AGE RELATED HEARING LOSS AND COGNITIVE DECLINE II: Mechanisms and Effect of Cochlear Implantation
 

11.3.2018

Background

An expanding literature indicates that age related hearing loss (ARHL) is associated with age related cognitive decline (ARCD).  This was discussed in the April 2016 blog in this series suggesting that memory and concentration both decline 30 – 40% faster in older adults who have hearing loss and that the risk of dementia increases proportionately with the degree of hearing loss.  In an aging mouse model, deafened mice had poorer cognitive function over time than normal hearing controls—inferring that the relationship may be causative. (References cited in April 2016 Blog.)

What’s New

The Lancet Commission on Dementia recently concluded that appropriate treatment of hearing loss may reduce the risk of dementia by up to 9% and that hearing loss is the leading treatable risk factor for dementia. (1)   Uchida et al. have described three mechanisms (and an artifact) by which ARCD and cognitive decline may be causally related. (2)

Possible Mechanisms

  1. Cognitive load hypothesis (Causal relationship between ARHL and ARCD).  Cognitive load refers to the amount of information processing required to perform a task.  If a task requires too much processing, performance is reduced because of a capacity limitation thought to be in working memory.  Older adults with hearing loss expend more attention and concentration (greater cognitive load) in listening than do their normal hearing counterparts.  This may deplete cognitive reserve required for other cognitive employment. (3)

  2. Cascade hypothesis (Causal relationship).  ARHL is associated with changes of brain morphology (neural plasticity) in older adults.  For example, ARHL subjects have smaller brain volume than age-matched normal-hearing peers (4,5) as well as accelerated rates of brain atrophy when followed over time.  (6) In fMRI studies, the degree of hearing loss predicted the volume of gray matter activation in the primary auditory cortex, thalamus, and brainstem. (7) Thus, in cascade theory, hearing loss may lead to changes in brain structure and function which may lead to ARCD, depression, social isolation, and behavioral involution.  Brain atrophy may also cascade into cognitive load issues.

  3. Common cause hypothesis (Non-causal relationship).  Common neurodegenerative process(es) in the aging brain may be responsible for both ARHL and ARCD.  Leading suspects include microcirculatory insufficiency, general health, oxidative stress, smoking, diabetes, cardiovascular and large vessel cerebrovascular disease, and genetic factors.  For example, the APOE gene encodes for Apolipoprotein E protein that has been associated with both neurodegenerative conditions such as central hearing loss and Alzheimer disease. In this theory, ARHL and ARCD may be caused by the same underlying processes but one does not cause the other. (8)

  4. Overdiagnosis    (Non-existent relationship)  It remains possible that hearing loss results in poor performance on neuropsychological tests leading to misdiagnosis of ARCD.  This notion is similar to that of culture-unfair IQ tests leading to misrepresentation of low intellect. In a study that supports this theory, use of ear plugs on older adults with normal cognitive test results caused artifactual ARCD.

Cochlear implants and ARCD

Lin et al (9) demonstrated that the rate of ARCD is directly related to the severity of hearing loss.  It follows that rehabilitation of severe-profound HL with cochlear implants may have a greater effect on ARCD than rehabilitation of mild-moderate HL with hearing aids.

Mosnier et al. (10) reported results of 37 implanted older adults who had abnormal scores on 2 or 3 of 6 cognitive tests (i.e.: ARCD) before surgery.  At 1-year post-op, 30 (81%) showed improvement with abnormal cognitive scores on 0 or 1 of the 6 tests. Thirty-one ARCD/implanted subjects were re-tested > 5 years post-op.  Ten (32%) returned to normal cognitive function, 19 (61%) remained stable and 2 (6%) progressed to dementia. (11)

Recently, Claes et al. (12) described the 12-month results of a planned 10-year prospective cohort study of cochlear implantation and ARCD in 20 severely hearing-impaired subjects > 55 years of age.  Significant improvements were found in total cognitive scores (p < 0.001), immediate (p < 0.005) and delayed memory (p < 0.002) and attention (p < 0.047).  However, the authors also found that after one year, the implanted patients showed significantly greater ARCD than normal hearing controls and suggested routine auditory and cognitive rehabilitation for implanted patients with ARCD. (13)

Take Home

Age related cognitive hearing loss is related to cognitive decline and is considered to be the leading treatable cause of dementia.  Three hypothetical mechanisms for the relationship of ARHL and ARCD include Cognitive Load, Cascade, and Common Cause. Early reports of longitudinal cohort studies indicate a beneficial effect of cochlear implantation on cognitive decline in older adults with ARHL.  Further studies of the effects of cognitive and language training after CI in older adults are called for.

References

  1. Livingston G, Sommerlad A, Orgeta V, Costafreda SG, Huntley J, Ames D, et al. Dementia prevention, intervention, and care. Lancet 2017;390 (10113):2673–734.

  2. Uchida Y, Sugiura S, Nishita Y, Saji N, et al.  Age-related hearing loss and cognitive decline—The potential mechanisms linking the two.  Auris Nasus Larynx. (2018) In press. https://doi.org/10.1016/j.anl.2018.08.010

  3. Sweller J, Ayres PL, Kalyuga S.  Cogniive load theory. New York; London: Springer, 2011.

  4. Lin FR, Ferrucci L, An Y, et al.    Association of hearing impairment with brain volume changes in older adults. Neuroimage (2014) 15: 84-92.   

  5. Rigters SC, Bos D, Metselaar M, Roshchupkin GV, Baatenburg de Jong RJ, Ikram MA, et al. Hearing impairment is associated with smaller brain volume in aging. Front Aging Neurosci 2017;9.  

  6. Golub JS. Brain changes associated with age-related hearing loss. Curr Opin Otolaryngol Head Neck Surg 2017;25(5):347–52.

  7. Peelle JE, Troiani V, Grossman M, Wingfield A. Hearing loss in older adults affects neural systems supporting speech comprehension. J Neurosci 2011;31(35):12638–21643.

  8. Mener DJ, Betz J, Yaffe K, et al. Apolipoprotein E allele in older adults. Am J Alzheimers Dis Other Demen 2016;31(1):34–9)   

  9. Lin FR, Yaffe K, Xia J, et al. Hearing loss and cognitive decline among older adults. JAMA Intern Med 2013;173:293–9.

  10. Mosnier I, Bebear JP, Marx M, Fraysse B, Truy E, et al. Improvement of cognitive function after cochlear implantation in elderly patients. JAMA Otolaryngol Head Neck Surg 2015;141 (5):442–50.

  11. Mosnier I, Vanier A, Bonnard D, et al. Long-Term Cognitive Prognosis of Profoundly Deaf Older Adults After Hearing Rehabilitation Using Cochlear Implants. J Am Geriatr Soc. 2018 Aug;66(8):1553-1561.  

  12. Claes AJ, Van de Heyning P, Gilles A, et al.  Cognitive Performance of Severely Hearing-impaired Older Adults Before and After Cochlear Implantation: Preliminary Results of aProspective, Longitudinal Cohort Study Using the RBANS-H.  Otol & Neurotol, Vol. 39, 2018.

  13. Claes AJ, Van de Heyning P, Gilles A, et al.  Impaired Cognitive Functioning in Cochlear Implant Recipients Over the Age of 55 Years: A Cross-Sectional Study Using the Repeatable Battery for the Assessment of Neuropsychological Status for Hearing-Impaired Individuals (RBANS-H).  Front Neurosci. 2018 Aug 24;12:580. doi: .3389/fnins.2018.00580. eCollection 2018.

 
 
Auditory-Verbal Practice: Access to Listening and Spoken Language (LSL) for Children with Cochlear Implants
 

September 2018


Background

Cochlear implants have established a remarkable record for improving hearing and language, educational, and social outcomes in pre-linguistic deaf and hard-of-hearing children.  Nonetheless, despite continuous improvements, in most cases the quality of auditory input with CIs is not sufficient for implanted children to develop age-level language without habilitation.  

Nearly 20 years ago, Hodges et al.(1) and Cullington et al.(2) demonstrated that implanted children who are enrolled in auditory-verbal therapy (AVT) programs performed significantly better than those in total communication (TC) programs on common batteries of speech perception and language development respectively.  More recently, Geers et al reported “compelling support…for the benefits of spoken language input for promoting verbal development in children implanted by 3 years of age.”(3)   

AVT is also referred to as Listening and Spoken Language (LSL), “the application and management of the most current hearing technologies, in conjunction with specific strategies that foster listening and spoken language conversations, through artful coaching of the child’s parents”(4). One important goal of LSL intervention is that children achieve age-appropriate literacy skills by third grade.

LSL intervention begins ideally at the time the child is initially diagnosed with hearing loss. The LSL professional is essential not only for facilitating listening and spoken language development, but in conditioning the child to respond to sound in preparation for early behavioral audiometry, guiding parents in managing hearing technology, providing critical diagnostic information on the child’s functional auditory skill development and preparing the child for the CI signal. As the member of the CI team who sees the child most frequently, the LSL professional can provide diagnostic information (a process called diagnostic therapy) on the status of the hearing aid trial period which can reduce the time for resolution of candidacy.

The AG Bell Academy for Listening and Spoken Language Specialist awards LSLSTM certification with two designations, Cert. AVT and Cert. AVEd to qualified professionals who have met rigorous academic, professional, post-graduate education and mentoring requirements, and have passed a certification exam.  Typically, LSLS certified practitioners are licensed audiologists, speech-language pathologists, or educators of the deaf who have acquired additional training and experience in listening and spoken language theory and practice.

Nicholas and Geers (5) have shown that children who receive AVT and are implanted at 6–12 months of age achieve significantly higher scores on all studied measures of language development than those implanted at 12-18 months.  Further, the advantages of implantation at 6-12 months remain constant at 4.5 years and 10.5 years of age. (6)  These findings underlie the value of early resolution of the hearing aid trial.


New Information

Conversely, Geers et al. (7) found that early exposure to sign language negatively affects CI outcomes.  In a controlled, prospective nationwide study of implanted children, those with sign language exposure exhibited a statistically significant disadvantage in spoken language and reading.  Only 39% of implanted children with exposure to ASL achieved age-appropriate spoken language compared to 70% of those without sign language exposure.

A 2016 systematic review by Kaipa and Danser (8) included 14 studies assessing AVT intervention with implanted children.  Significant benefits of AVT over other forms of habilitation were found in all three studied domains: receptive and expressive language, speech perception, and mainstreaming.  A similar systematic review of the relative efficacy of AVT and TC for language development in implanted children was completed in 2017. In that study, Shoffner (9) demonstrated statistically significant advantages of AVT over TC for measures of receptive and expressive language.

Unfortunately, many CI centers have reported lack of access to AVT/LSL services for their implanted patients.  Results of an Institute for Cochlear Implant Training (ICIT) nationwide survey of CI teams, circulated by the American Cochlear Implant Alliance (ACIA) (August 2018), indicate that 34.4% of implanted children in the US receive American Sign Language, Total Communication, or no formal habilitation (n = 87 CI centers).  (This membership survey cannot be considered a scientific sample.)

Also in August 2018, the AG Bell Academy (Academy) reported 610 Certified LSL professionals in the US.   According to the Academy, five states have no LSLS and 14 have fewer than three LSLS per state.

Early intervention programs in public-school systems often provide habilitation at no cost to families but, for a variety of reasons, such as cost or the predilection of deaf educators for American Sign Language (ASL), many tend to maintain TC approaches and offer limited access to LSL services.  Noblitt et al (10) have identified several barriers to habilitation of pediatric CI recipients and call for “efforts to expand access to care… to maximize CI benefit.”


Take Home

LSL/AVT is an effective form of habilitation of deaf children with CIs.  An emerging literature suggests three principles of maximizing listening and spoken language development:  early identification, cochlear implantation below the age of 12 months, and LSL habilitation. Additionally, post-linguistically deafened children and adults may also benefit from LSL techniques.  Our best estimate appears to suggest that approximately one-third of implanted children in the US undergo ASL, TC or informal habilitation. It is likely that CI outcomes in pre-linguistic children could be markedly improved by increasing accessibility of LSL to CI teams and their patients. Further efforts to increase the availability of LSL-oriented interventionists will be necessary.


References

  1. Hodges AV, Dolan Ash M, Balkany TJ, Schloffman JJ, Butts SL. Speech perception results in children with cochlear implants:  contributing factors. Otolaryngol Head Neck Surg. 1999 121: 31-34.

  2. Cullington H, Hodges AV, Butts SL, Dolan-Ash S, Balkany TJ.  Ann Otol Rhinol Laryngol Suppl. 2000 Dec; 185:121-3

  3. Geers AE, Mitchell CM, Warner-Czyz A, Wang N-Y, Eisenberg LS, CDaCI Team. Early Sign Language Exposure and Cochlear Implantation Benefits. Pediatrics. 2017;140(1): e20163489

  4. Estabrooks, W., MacIver-Lux, K., & Rhoades, E.A. (2016). Auditory-verbal therapy. (p. 4) San Diego: Plural Publishing.

  5. Nicholas JG, Geers AE.  Spoken Language Benefits of Extending Cochlear Implant Candidacy Below 12 Months of Age. Otol Neurotol. 2013 April; 34(3): 532–538.

  6. Geers AE, Nicholas JG.  Enduring Advantages of Early Cochlear Implantation for Spoken Language Development.   J Speech Lang Hear Res. 2013 April ; 56(2): 643–655.

  7. Geers AE, Mitchell CM, Warner-Czyz A, et al. Early Sign Language Exposure and Cochlear Implantation Benefits. Pediatrics. 2017;140(1):e20163489

  8. Kaipa, R., & Danser, M. L. (2016). Efficacy of auditory-verbal therapy in children with hearing impairment: A systematic review from 1993 to 2015. International Journal of Pediatric Otorhinolaryngology, 86, 124-134.

  9. Shoffner A.  Efficacy of Auditory-Verbal Therapy over Total Communication (TC) for Language Outcomes in Children with Cochlear Implants:  a Systemic Review. Master’s Thesis The Graduate School of the University of Alabama, Tuscaloosa, Alabama (2017)

  10. Noblitt B, Alfonso KP, Adkins M, Bush ML.  Barriers to Rehabilitation Care in Pediatric Cochlear Implant Recipients. 2018.  O&N 39: e307-313.

 

The views, information, and opinions below are solely those of the individuals commenting and do not necessarily represent those of ICIT.

Electrocochleography and Cochlear Implantation
 

Introduction

Electrocochleography is a method of recording electrical potentials generated in the cochlea in response to acoustic stimuli. For purposes of the following discussion, they are listed below:

Name Principle Site of Origin Potential Type
1. Summating Potential (SP) Outer hair cells DC
2. Action Potential (AP, CAP) Auditory nerve axons DC
3. Cochlear Microphonic (CM) Outer hair cells AC
4. Auditory nerve neurophonic (ANN) Auditory nerve dendrites AC


Clinicians are familiar with extracochlear recording of SP and AP in the diagnosis of Meniere’s disease and CM in the diagnosis of auditory neuropathy spectrum disorder. However, intracochlear recording of ECochG with CI electrodes is a more recent development. Calloway et al.1 demonstrated that CI recipients with severe to profound hearing loss routinely have measurable ECochG responses to acoustic stimuli when recording with an intracochlear CI electrode.

Over the past ten years or so, Craig Buchman, Oliver Adunka and their colleagues, as well as other teams, have been investigating the intraoperative use of ECochG to monitor electrode insertion trauma during cochlear implantation.1-6 In 2010, Adunka et al.2 demonstrated in gerbils that CM and AP can be used as physiologic markers of electrode contact with the basilar membrane and may be able to provide forewarning to the surgeon to avoid permanent loss of neural function or histological damage.

What’s New

Recently Koka et al.6 reported monitoring ECochG in human subjects during CI electrode insertion to estimate electrode position and conservation of residual hearing. ECochG, specifically the CM, was recorded from the apical electrode (closest to low frequency place) in response to 110 dB SPL tone bursts. As interpreted by a pragmatic algorithm based on amplitude and phase, changes in ECochG correctly identified electrode array position (S. tympani vs. vestibuli) in 26 (82%) of 32 human subjects while 6 (18%) electrodes were wrongly identified as translocated (sensitivity = 100%, specificity = 77%; positive predictive value = 54%, and negative predictive value = 100%). ECochG changes could be seen when an electrode first contacted the basilar membrane providing advanced warning of translocation from S. tympani to vestibuli.

Intracochlear ECochGs have also been recorded from implanted guinea pigs which were then studied histologically by Helmstaedter et al.7 The authors suggest that the SP can be used to identify the pitch place of individual electrode contact and the AP was generally correlated with the degree of electrode insertion trauma. For further information on intracochlear measurements of ECochG potentials, Bester et al.8 have provided a detailed characterization.

Finally, Koka et al.9 explored the relationship between ECochG thresholds and behavioral thresholds in a group of CI recipients tested on the same postoperative day. These studies showed strong correlation (r=0.87) with a mean difference of -3.2 dB (+/- 9dB) suggesting that ECochG may accurately predict audiometric threshold.

Take Home

ECochG may have several important applications in cochlear implantation:

- Assess electrode array location (S. tympani/ vestibuli)
- Asses the pitch place of individual contacts and the cochleotopic boundary of residual low frequency hearing
- Identify real-time onset of one type of electrode insertion trauma (interaction with the basilar membrane prior to permanent damage)
- Determine audiometric thresholds postoperatively
- Help develop minimally-traumatic electrodes (MTEs) and insertion techniques
- Assist in surgical training of neural conservation techniques.

Like the facial nerve monitor, ECochG may provide adjunctive forewarning of intra-cochlear neural trauma. The use of ECochG has the potential to improve CI outcomes by conserving functional neural structures, residual hearing, and balance.

References

  1. Calloway NH, Fitzpatrick DC, Campbell AP, Iseli C, Pulver S, Buchman CA, Adunka OF. Intracochlear electrocochleography during cochlear implantation. Otology and Neurotology 2014; 35: 1451-1457.

  2. Adunka OF, Mlot S, Suberman TA, Campbell AP, Surowitz J, Buchman CA, Fitzpatrick DC. Intracochlear Recordings of Electrophysiological Parameters Indicating Cochlear Damage. Otology & Neurotology. 2010; 31:1233-1241.

  3. Harris MS, Riggs WJ, Giardina CK, O'Connell BP, Holder JT, Dwyer RT, Koka K, Labadie RF, Fitzpatrick DC, Adunka OF. Patterns Seen During Electrode Insertion Using Intracochlear Electrocochleography Obtained Directly Through a Cochlear Implant. Otol Neurotol. 2017 Dec;38(10):1415-1420.

  4. Riggs WJ, Roche JP, Giardina CK, Harris MS, Bastian ZJ, Fontenot TE, Buchman CA, Brown KD, Adunka OF, Fitzpatrick DC. Intraoperative Electrocochleographic Characteristics of Auditory Neuropathy Spectrum Disorder in Cochlear Implant Subjects. Front Neurosci. 2017 11:416-422.

  5. Harris MS, Riggs WJ, Koka K, Litvak LM, Malhotra P, Moberly AC, O'Connell BP, Holder J, Di Lella FA, Boccio CM, Wanna GB, Labadie RF, Adunka OF. Real-Time Intracochlear Electrocochleography Obtained Directly Through a Cochlear Implant. Otol Neurotol. 2017 Jul;38(6):e107-e113.

  6. Koka K, Riggs WJ, Dwyer R, Holder JT, Noble JH, Dawant BM, Ortmann A, Valenzuela CV4, Mattingly JK, Harris MM, O'Connell BP, Litvak LM, Adunka OF, Buchman CA, Labadie RF. Intra-Cochlear Electrocochleography During Cochear Implant Electrode Insertion Is Predictive of Final Scalar Location. Otol Neurotol. 2018 Sep;39(8):e654-e659.

  7. Helmstaedter V, Lenarz T, Erfurt P1, Kral A, Baumhoff P. The Summating Potential Is a Reliable Marker of Electrode Position in Electrocochleography: Cochlear Implant as a Theragnostic Probe. Ear Hear. 2018 Jul/Aug;39(4):687-700.

  8. Bester CW, Campbell L, Dragovic A, Collins A, O'Leary SJ. Characterizing Electrocochleography in Cochlear Implant Recipients with Residual Low-Frequency Hearing. Front Neurosci. 2017 Mar 23;11:141.

  9. Koka K, Saoji AA, Litvak LM. Electrocochleography in Cochlear Implant Recipients with Residual Hearing: Comparison with Audiometric Thresholds. Ear Hear. 2017 May/Jun;38(3):e161-e167.
 
 

 

       
      CI Tip Fold-Over II: Intraoperative Electrophysiology and Imaging
       

      Background

      Intraoperative evaluation of CI electrodes has been available for many years, although many CI centers have found testing to be unnecessary in routine cases. Such judgments have been based on a low overall rate of positive findings, a relatively high rate of false-positives (presumably due to air in the cochlea), extended anesthesia time, non-reimbursable audiology time, cost, the rarity of out-of-the-box failures, exposure to radiation, etc. However, the advent of very delicate electrodes, which may be susceptible to tip foldover (ICIT Surgeon’s Blog 8.28.17) suggests the need to re-evaluate the advisability of routine electrode evaluation.

      Intra-operative evaluations consist of electrophysiological tests and X-ray imaging. The former include electrically evoked compound action potential (ECAP), electrical impedance (EI), and spread of excitation (SOE). ECAP is a measure of neural responses. EI can identify open circuits (high impedance) and short circuits (low impedance). SOE represents the location of the electrical field around each electrode and overlap suggests tip foldover. These tests are evaluated using reverse telemetry. Intraoperative ECoG is evolving and a number of X-ray imaging studies (plain films, fluoroscopy, 3-D rotational X-ray, CT scan, etc.) are used in evaluation of tip foldover.

      New Information

      Page, Murphy, Kennett, Trinidade et al. of the University of Arkansas for Medical Sciences(1) recently reported that, based on ECAP and EI, a backup device was used in only 2 of 266 (0.8%) consecutive implants performed between 2010 and 2015. In one case, the backup device showed the same high impedances (open circuit) as the initial device but was left in place and worked normally post-op (probably due to resorption of air). The authors appropriately make a case against routine intraoperative electrophysiological testing of the CI electrodes used during the study period. However newer, more delicate perimodiolar electrode arrays were not evaluated and X-ray imaging was not routinely performed.

      Zuniga, Rivas, Hedley-Williams, Gifford et al. of Vanderbilt University(2) reported that foldover was associated with perimodiolar electrodes (5 of 6 cases) but was uncommon (<2%) in electrodes used prior to mid-2015. Some of their important findings regarding foldover:

      1. SOE had limited predictive value

      2. foldover was not apparent to the surgeon during insertion

      3. foldover was not associated with aversive stimuli to the patient

      4. diagnosis was made by CT scan

      5. deactivation of overlapping electrodes resulted in improved hearing.

      Garaycochea, Manrique-Huarte and Manrique(3) report failure of ECAP and EI to identify tip foldover with a newer perimodiolar array. Like Zuniga et al(2), diagnosis was made by X-ray imaging. It appears that intraoperative imaging has a higher predictive value for foldover and may be less expensive than electrophysiology (the cost of an audiologist’s time.)

      Take Home

      Tip foldover appears to be more common in perimodiolar electrodes. Although many CI surgeons agreed that intraoperative electrode evaluation may have been unnecessary using previous electrodes, it may be time to reconsider that decision when implanting very delicate perimodiolar electrodes. At this time, X-ray imaging appears to have higher predictive value in identifying rollover. Further study is called for to determine the actual rate of tip foldover in newer arrays.

       

      References

      1. Page JC, Murphy L, Kennett S, Trinidade A, Frank R, Cox M, Dornhoffer JL. The influence of intraoperative testing on surgical decision making during cochlear implantation. Otol Neurotol 2017 38(8): 1092-1096.

      2. Zuniga GM, Rivas A, Hedley-Williams A, Gifford RH, Dwyer R, Dawant BM, et al. Tip foldover in cochlear implantation: Case series. Otol Neurotol 2017 38:199-206.

      3. Garaycochea O, Manrique-Huarte R, Manrique M. Intra-operative radiological diagnosis of a tip roll-over electrode array displacement using fluoroscopy, when electrophysiological testing is normal: the importance of both techniques in cochlear implant surgery. Braz J Otorhinolaryngol. 2017.  http://dx.doi.org/10.1016/j.bjorl.2017.05.003

       
      Preventing Electrode Tip Fold-Over
       

      Background

      Electrode array design has continuously evolved to reduce insertion trauma and improve hearing conservation. However, one downside of some delicate (smaller diameter, more flexible) electrodes has been a tendency for tip fold-over. Tip fold-over may occur during insertion when the electrode array tip impinges the modiolar wall (or other structure) and is temporarily held stationary while the more proximal electrode advances past it. The phenomenon has also been called “tripping” and may be more common in perimodiolar electrodes.(1,2) Tip fold-over may result in a variety of negative consequences, ranging from the need to program-out electrode contacts all the way to removal and replacement of the entire electrode array. Fold-over is also associated with cochlear insertion trauma.

      New Information

      Prof. Angel Ramos and colleagues at Las Palmas University have recently analyzed insertion techniques for a newer delicate perimodiolar electrode array using both a plastic model of the cochlea and human cadaver temporal bones.(1) Dynamic insertion was studied with fluoroscopy while final electrode position was studied with cone beam CT. The authors analyzed the outcomes of the manufacturer’s recommended insertion technique and the effects of three common errors that could be made in surgery:

      1. Improper alignment (rotation) of the pre-curved electrode at the cochleostomy (should be toward the modiolus);

      2. Over-insertion of the electrode ‘sheath’;

      3. Pre-extrusion of the array from the sheath prior to proper positioning of the sheath.

      Using the recommended technique, the authors report good results with no tip fold-overs. However, in each of the three technique-error conditions, tip fold-over was common: improper alignment--100%; over-insertion—60%; pre-extrusion—40%. Imaging also demonstrated dislocation of the electrode into Scala vestibuli in most bones with tip fold-over. It should be noted that, typical of anatomic studies, the number of insertions in this study are limited.

       

      Take Home

      As electrodes become more delicate, the potential for tip fold-over becomes more substantial. This may be especially true with perimodiolar electrodes. Ramos et al. demonstrate the need meticulously to follow good surgical techniques and to be aware of common errors.

      It is important to remember that initial studies of new electrodes are performed by surgeons who were highly involved in the experimental development of the electrode over a period of months or years. These surgeons are highly aware of the characteristics of the new array as well as what can go wrong during insertion. Subsequent FDA pre-market approval/CE Marking studies are usually carried out by a small group of highly selected senior CI surgeons who receive more training on a new electrode than other practicing CI surgeons usually do. As a result, sometimes surgical issues are not apparent until the new electrodes are released for widespread use.

      For these reasons it is important to obtain specific training on any new device prior to performing the procedure. Manufacturers will provide this on request in a number of ways. Reading the surgeon’s manual and having a rep standing by in the O.R. for a first case are helpful but may not be sufficient.

      References

      1. Ramos-Macias A, De Miguel AR, Falcon-Gonzalez JC. Mechanisms of electrode fold-over in cochlear implant surgery when using a flexible and slim perimodiolar electrode array. Acta Oto-Laryngol 2017. PAP DOI:10.1080/00016489.2016.127149.

      2. Briggs RJ, Tykocinski M, Xu J, et al. Comparison of round window and cochleostomy approaches with a prototype hearing preservation electrode. Audiol Neurotol. 2006;11:42–48.

       
      The American Cochlear Implant (ACI) Alliance
       

      By The Institute for Cochlear Implant Training

      The American Cochlear Implant (ACI) Alliance is a not-for-profit membership organization created with the purpose of eliminating barriers to cochlear implantation. The ACI Alliance membership spans clinicians and scientists from across the cochlear implant continuum of care including otolaryngologists, audiologists, speech pathologists, educators, psychologists, and others in cochlear implant teams. Parents of children with cochlear implants, adult recipients, and other advocates for access to care are also active members. Our activities include research, advocacy and awareness initiatives designed to improve access to CI care. The ACI Alliance sponsors an annual clinical research meeting that provides opportunities for scientists, clinicians and others to share information.

      http://www.acialliance.org/

       
      Audiologic Management of CI Patients has become Increasingly Complex
       

      Background

      Over the past 3 years, the Institute for Cochlear Implant Training (ICIT) Advanced Surgeons’ Training Course has provided in-depth education for over 60 CI surgeons from the US and around the world, which could improve outcomes of thousands of CI recipients. Similar training and education needs to exist for audiologists. This blog describes some of the areas that are covered in the Advanced Audiology CI Course (AAC), which was developed by ICIT to meet this educational need.

      It is the responsibility of the cochlear implant (CI) team, which typically includes the implant surgeon, audiologist, and speech-language pathologist, as well as other professionals, to determine who is an appropriate candidate to receive a CI. It is also their responsibility to ensure the device is adequately placed, appropriately programmed, and to monitor device function to ensure the patient is receiving optimal benefit from its use. In recent years, the responsibilities of CI audiologists have expanded considerably and become increasingly complex as technological advances with external and internal devices have accelerated at fast rates.

      New Information

      Early on, many CI teams declined to implant patients with cochlear anomalies such as cochlear malformations or ossification. Today, it is estimated that approximately 20-30% of children who receive a CI have some type of cochlear abnormality.(1) This increase in access is the result of several factors, including improvements in preoperative radiographic and electrophysiologic tests(2), technological advances in internal devices (such as split and compressed arrays), and improved surgical device placement. This makes it necessary for audiologists to understand the anatomy and physiology of the ear, particularly as it relates to hearing and electrical current. For example, a patient with an ossified cochlea may receive a split electrode array. The audiologist must understand the reason for choosing such a device and be able to counsel the patient regarding expected outcomes. Mapping the device necessitates understanding the physiology of both the normal and abnormal inner ear in order to manage the flow of current that will be delivered to the electrodes located in various areas of the cochlea. This includes a basic understanding of mapping parameters that can be changed or tried when difficult situations, such as stimulation of the facial nerve, occur.

      Over the years, advances in speech processing have resulted in great increases in speech recognition scores obtained by CI recipients. In early trials, adults with CIs obtained scores of approximately 15% on CNC Monosyllabic Words and approximately 35% on simple CID Sentences.(3) More recently, these scores have increased to approximately 58% for CNC Words and over 80% for the more challenging AzBio Sentences.(4) In order to optimize performance and have their patients attain such scores, CI audiologists need to have a basic understanding of sound processing strategies, as well as understand the parameters that can be manipulated or changed to optimize the patient’s ability to hear with the device. Mapping a CI comes with great responsibility; provision of an inappropriate map can result in months or years of less than optimal hearing and may lead to greatly reduced outcomes for both children and adults. Conversely, provision of an optimized map can lead to life-changing results.

      Recent advances in electrophysiologic tests have increased their use in clinical care. Electric auditory brainstem response (EABR) testing has been used for several years to verify electric stimulability of the ear prior to implantation.(5) Intraoperatively, electrically evoked compound action potentials (ECAPS) have been used to determine a baseline reference for future audibility measurements when mapping the speech processor(6) while more recently, researchers have described the use of electrocochleography during surgery to help predict postoperative hearing preservation(7), and to modify surgical procedure, reduce trauma, and increase preservation of residual hearing.(8) Post-implant, ECAPS are successfully used with all 3 of the currently available devices to confirm that mapping measures of threshold, comfort level, or M level are falling within an area of audibility.

      Recent approval of the Nucleus Hybrid and the MedEl EAS have increased the complexity of decisions regarding candidacy for a cochlear implant. Previously, determination of candidacy for a CI was rather straightforward: patients were only considered to be candidates for a CI if they demonstrated little or no benefit from amplification. Today, patients are being evaluated for a CI even though they demonstrate word or sentence recognition scores in the high 70s (percent correct). This is appropriate, as the results of recent clinical trials indicate that hearing preservation is possible for many patients and that such patients hear best when they are fit with devices that utilize acoustic stimulation for low frequency hearing combined with electrical stimulation for enhanced high frequency hearing. Recent studies also indicate that many patients demonstrate bimodal benefit when the hearing received with a cochlear implant is combined with the acoustic hearing in the contralateral/non-implanted ear.(9) These advances have not only changed how we look at candidacy, but have also impacted the tests being used to determine candidacy and evaluate performance. Tests are becoming increasingly complex, with greater use of more difficult sentences and increased use of test materials in noise.

      Another recent change in CI management includes continued increase in the provision of CIs to pediatric patients with disabilities in addition to hearing loss.(10-11) Unfortunately, adult patients are not immune from this phenomenon; Lin and colleagues found that adults with hearing loss demonstrated a 30-40% increase in rate of cognitive decline when compared to adults with normal hearing. They also found that adults with severe hearing loss were at five times the risk of developing dementia than adults with normal hearing. Such patients can be challenging to manage and often require modifications to mapping and testing procedures in order to optimize outcomes.

      Lastly, one aspect of patient management that is frequently overlooked is clinic efficiency. Recent changes in reimbursement make it necessary for audiologists to not only consider the quality of care they provide, but to also consider the sustainability of their program and the services they provide.(12) This includes designing programs that are efficient, cost-effective and will last over time to serve the life-long needs of patients with CIs.

      Take Home

      Audiological management of CI patients has become increasingly complex. It is the responsibility of the CI team to remain current in regards to recent advances and improvements in all aspects of care. For the CI audiologist, this includes preoperative determination of candidacy, optimization of CI mapping, post-operative monitoring of device function and patient performance, and knowledge of various cochlear anomalies and disabilities and how they will impact outcomes with both children and adults. The Institute for Cochlear Implant Training (ICIT), with its introduction of the Advanced Audiology CI Course (AAC), is one option for facilitating continued learning and expansion of knowledge by CI audiologists.

      References:

      1. Coticchia JM1, Gokhale A, Waltonen J, Sumer B. Characteristics of sensorineural hearing loss in children with inner ear anomalies. Am J Otolaryngol. 2006 Jan-Feb; 27(1):33-8.

      2. Cushing SL, Blaser SI, Papsin BC. Medical and Radiological Issues in Pediatric Cochlear Implantation. In Young and Kirk (Eds) Pediatric Cochlear Implantation, Learning and the Brain. Springer (2016), New York, New York.

      3. Dowell R, Mecklenburg D, Clark G. Speech recognition for 40 patients receiving multichannel cochlear implants. Arch Otolaryngol Head Neck Surg, (1986); 112(10): 1054-1059.

      4. Runge CL, Henion K, Tarima S, Beiter A, Zwolan TA. Clinical Outcomes of the Cochlear™ Nucleus(®) 5 Cochlear Implant System and SmartSound™ 2 Signal Processing. J Am Acad Audiol. 2016 Jun; 27(6):425-40.

      5. Kileny PR, Zwolan TA. Pre-perioperative, transtympanic electrically evoked auditory brainstem response in children. (2004). Int J Audiol. 2004 Dec; 43 Suppl 1:S16-21.

      6. Muller A, Hocke T, Mir-Salim, P. Intraoperative findings on ECAP-measurement: normal or special case? Int J Audiol 2015 Apr; 54(4); 257-64.

      7. Adunka OF, Giardina CK, Formeister EJ, Choudhury B, Buchman CA, Fitzpatrick DC. Round window electrocochleography before and after cochlear implant electrode insertion. Laryngoscope 2016 May, 126(5): 1193-200.

      8. Mandalà M, Colletti L, Tonoli G, Colletti V. Electrocochleography during cochlear implantation for hearing preservation. Otolaryngol Head Neck Surg. 2012 May; 146(5):774-81.

      9. Illq A, Bojanowicz M, Lsiniski-Schiedat A, Lenarz T, Buchner A. Evaluation of the bimodal benefit in a large cohort of cochlear implant subjects using a contralateral hearing aid. Otol Neurotol 2014 Oct; 35(9).

      10. Edwards LC. Children with cochlear implants and complex needs: a review of outcome research and psychological practice. Journal of Deaf Studies and Deaf Education. 2007;12(3):258–268.

      11. Johnson KC, Wiley S. Cochlear implantation in children with multiple disabilities. In: Eisenberg LS, editor. Clinical management of children with cochlear implantation. Plural Publishing; San Diego, CA, USA: 2009. pp. 573–632.

      12. Huddle M, Tirabassi A, Turner L, Lee E, Ries K, Lin S. Application of Lean Sigma to the Audiology Clinic at a Large Academic Center. Otolaryng-Head and Neck Surgery 2016 Vol 154(4) 715-719.

       
      Terry Zwolan, Ph.D.
      Delayed Hearing Loss after Hearing Conservation Surgery
       

      Background

      Conservation of residual hearing during cochlear implantation has been a focused area of CI research since the first report in 1989.(1) Retention of low-frequency acoustic hearing may allow fine structure processing, enhance speech understanding in noise, sound localization, and music appreciation. Hearing conservation has been made possible by advances in surgical techniques, low-trauma electrodes and the use of steroids (see ICIT Surgeons’ Blog 7/1/15; 8/1/15; 12/1/15; 1/1/16; 2/1/16; 3/1/16; 12/5/16; 3/7/17).

      Although residual hearing is frequently conserved (not destroyed) during implantation, at this time there are no widely available methods to actively preserve it. Delayed loss of residual hearing after implantation is known to occur in a substantial number of patients.

      What’s New

      Scheperle, Tejani, Omtvedt, Brown, Abbas, Hansen, Gantz, Oleson, and Ozanne(2) recently described longer-term outcomes in 85 people with residual hearing who were implanted at the University of Iowa. Thirty-eight percent of subjects experienced delayed loss of residual acoustic hearing, often within the first year. No significant differences were found when comparing round window cochleostomy with bony cochleostomy or comparing four different electrode styles. These findings demonstrate excellent surgical technique and electrode design and direct our attention to reactive physiologic processes that are as yet undefined.

      Of particular interest, subjects with delayed precipitous drops in acoustic threshold also had abrupt changes in electrode impedance but not necessarily in ECAP findings. The authors suggest these findings may indicate a change in the electrode environment (e.g. a fibrotic response altering cochlear micromechanics) rather than the usual explanation—loss of stimulable neural elements. Prior studies support the notion that the extent of fibrous growth is related to progressive loss of acoustic hearing.(3,4)

      Take Home

      Cochlear implant surgeons perform minimally traumatic surgery to avoid damaging residual neural elements, but no methods are generally available actively to preserve those structures. In the Iowa study, 38% of subjects with initial conservation of acoustic hearing had subsequent delayed loss, usually within 12 months. Nonetheless, ECAPs were often not similarly diminished, a finding that may indicate a mechanical effect of the fibrous electrode sheath. Alternatively, it could indicate loss of cochlear hair cell function in excess of ganglion cell function. Look for further research in this domain. In the near future, drug eluting CI electrodes, neurotrophin-producing intra-cochlear cellular transplants, direct gene therapy, or other regenerative techniques may become available for actively preserving residual hearing.

       

       

       

      References

      1. Boggess WJ, Baker JE, Balkany TJ. Loss of residual hearing after cochlear implantation.Laryngoscope. 1989. 99:1002-5.

      2. Scheperle RA, Tejani VD, Omtvedt JK, Brown CJ, Abbas PJ, Hansen MR, Gantz BJ, Oleson JJ, Ozanne MV. Delayed changes in auditory status in cochlear implant users with preserved acoustic hearing. Hear Res (2017) 350: 45-57.

      3. O'Leary SJ, Monksfield P, Kel G, Connolly, T, Souter MA, Chang A, Marovic P, O'Leary JS, Richardson R, Eastwood H. 2013. Relations between cochlear histopathology and hearing loss in experimental cochlear implantation. Hear Res. 298, 27-35.

      4. Wilk M, Hessler R, Mugridge K, Jolly C, Fehr M, Lenarz T, Scheper V, 2016.

       
      Advanced Audiology CI Course (AAC)
       

      By The Institute for Cochlear Implant Training

      May-July 2017

      CochlearImplantTrainingAAC.com

      Designed to challenge both new and developing audiologists who wish to accelerate their knowledge of programming and improve care for the patients they serve.

      10 week online web class

      • Recommended reading and video materials

      • Discussion Board

      • Weekly live 90 minute web class (Tuesday's at 8p EST, starting 5.16.17 through 7.18.17)

      Hands-on Advanced Programming Workshop

      • Saturday, July 29th (1-5p), following the conclusion of ACIA at Hilton Union Square Hotel, San Francisco

      • Instructors: Dr. Terry Zwolan, Dr. Meredith Holcomb, and Dr. Cache Pitt

      Module topics presented by leading research and clinical experts:

      1. Expanded Candidacy & the CI Team, Dr. Terry Zwolan

      2. Anatomy, CAS, and Medical Assessment, Dr. Craig Buchman

      3. Processing Strategies, Dr. Jace Wolfe

      4. Electrophysiologic testing and CI, Dr. Lisa Potts

      5. CI Mapping, Dr. Rene Gifford

      6. Evaluating Communication Needs/Outcomes, Dr. Terry Zwolan

      7. Etiologies and Patients with Additional Disabilities, Dr. Holly Teagle

      8. Hybrid/Bimodal, Dr. Camille Dunn

      9. ABI/SSD, Dr. William Shapiro

      10. Clinic Efficiency, Dr. Terry Zwolan

       
      Terry Zwolan, Ph.D.
      CI Outcomes: The Effect of Spiral Ganglion Survival
       

      Background

      Although CI outcomes are generally good and consistently improving, there continues to be a wide range of performance in speech recognition. Disparate outcomes have been attributed to several clinical variables including:

      • Age at implantation

      • Cognitive function

      • Use of signed language

      • Duration of deafness

      • Surgeon experience

      • Auditory-Verbal Therapy

      • Pre-op hearing aid use

      • Percent active electrodes

      • Scalar position of electrode

      • Residual hearing

      • Device, electrode, program

      • Socio-economic status

      However, in examining these factors a retrospective study of 2,251 CI recipients showed that even a combination of the most significant variables accounted for only about 10 to 20% of outcome variability.(1,2) Some other determinant(s) must have a substantial impact on performance.

      What’s New

      McClellan et al (2014)(3) of the University of North Carolina employed a novel analysis of ECOG potentials (which include contributions of both hair cell and neuron function, but are dominated by the latter.) The ECOG-TR sums response amplitudes at multiple frequencies to derive a “total response”. This test alone accounted for 40% of CI outcome variance in 32 subjects. Aside from its predictive value, this study suggested that residual spiral ganglion cell function may play an important role in CI outcomes. Support for this notion was to come from genetic studies using massively parallel sequencing techniques.

      In 2015, Wu et al(4) of the National Taiwan University reported that 12 children with poor CI performance (in speech perception, receptive and expressive language) tended to have more genetic mutations affecting the spiral ganglion than a matched group of 30 children with good outcomes. The authors found that organ of Corti mutations were associated with “good” results and ganglion cell mutations were associated with “poor” results. This makes sense since CIs bypass hair cells and synapses.

      A larger study of 155 adult CI subjects was recently (PAP 2017) reported by Shearer and colleagues from the University of Iowa(5) The authors categorized subjects as a sensory-genetic group (deleterious variants among 89 genes affecting hair cells or synapses) or neural-genetic group (deleterious variants among seven genes affecting the spiral ganglion.) Mutation of spiral ganglion-associated genes was associated with poorer results than mutation of organ of Corti-associated genes and accounted for 18% of the variance in speech perception outcomes, underscoring the importance of spiral ganglion cell function in CI outcomes.

      Take Home

      The importance of residual spiral ganglion function has been largely overlooked in assessing possible causes of CI outcome predictability and variability. This will change as physiologic and genetic methods of evaluating spiral ganglion survival and function in CI candidates become more prevalent.

      ECOG-TR can account for 40% of outcome variability and genetic testing for mutations in spiral ganglion cells account for 18%. Although widespread application of these techniques awaits further study, one thing has become clear: spiral ganglion cell survival and function play an important role in CI performance.

      References

      1. Lazard DS, Vincent C, Venail F, Van de Heyning, P, Truy, E, et al. Pre-, Per- and Postoperative Factors Affecting Performance of Postlinguistically Deaf Adults Using Cochlear Implants: A New Conceptual Model over Time. 2012 PLoS ONE 7, e48739–11.

      2. Blamey P, Artieres F, Baskent D, Bergeron F, Beynon AS, et al.. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants: an update with 2251 patients. 2013 Audiol. Neurootol. 18, 36–47.

      3. McClellan J.H, Formeister EJ, Merwin WH, Dillon M, Calloway N, Iseli C, et al. 2014. Otology & Neurotology 35, e245-e252.

      4. Wu CC, Lin YH, Liu TC, Lin KN, Yang WS, et al. Identifying Children With Poor Cochlear Implantation Outcomes Using Massively Parallel Sequencing. 2015. Medicine 94, e1073.

      5. Shearer AE, , Eppsteiner RW, Frees K, Tejani V, Sloan-Hagen C Black-Ziegelbein EA, et al. 2017 Hear Res (PAP, DOI: 10.1016/j.heares.2017.02.008).

       
      Development and Validation of the Cochlear Implant Surgical Competency Assessment Instrument
       

      Objective: We present a new instrument for evaluation of cochlear implant (CI) surgical skills and review its validation process.

      Methods: An instrument to assess CI surgical competency incorporated results of structured surveys of comprehensiveness sent to 30 international CI experts and US trainees. One-hundred evaluations of 28 residents, fellows, and practicing CI surgeons were completed. Surgical skills were evaluated by four experienced neurotologists (two raters per subject) using two temporal bones per subject. A training session was completed by 24 subjects between the first and second procedure. Comparison of two blinded rater’s scores per subject provided information on interrater reliability. Correlation of competency scores with degree of training and with improvement after a training session provided information on construct validity.

      Results: High levels of interrater reliability were confirmed by using the intraclass correlation coefficient. Construct validity was demonstrated by correlation of higher performance scores with increasing years of training, board certification, and fellowship training. Construct validity is also supported by improvement in scores after a CI training session as well as by acceptability surveys.

      Discussion: Data indicate that this instrument is an objective, accurate, and dependable procedure-specific instrument for evaluating CI surgical competency.

      Conclusion: The cochlear implant surgical competency assessment (CI-SCA) can be used to establish CI surgical competency, identify surgical skills that require remediation and demonstrate progress during training.

      *Check out this abstract published online ahead-of-print by Otology and Neurotology

       
      Vestibular Function and Development of Motor Skills in Implanted Children
       

      Introduction

      Progress in cochlear implantation programs allows a better understanding of speech development in children with prelingual profound hearing loss. Less understood is the impact of vestibular receptor disorders which can be associated with congenital deafness. These disorders can be congenital or result from the surgical procedure. Sensory preservation surgical techniques are effective for residual hearing(1-4) and have recently been proposed for preserving vestibular function. (CI Surgery Blog 12.5.16).

      Also, measurements of vestibular function(5-7), posture, and gait in these children has created a new area of interest, generating other questions, such as:

      1-Does the motor skill development in congenitally deaf children have a similar process to that of normal hearing children?

      2-How is the posture and gait performance in implanted children with congenital deafness?

      What’s New

      Recent studies from the Laboratory of Otoneurology, British Hospital, Department of Electrical Engineering, University Catolica Del Uruguay and Facultad de Medicina, Montevideo, Uruguay, demonstrate vestibular dysfunction in prelingual cochlear implant users and its impact on posture and gait. Postural control has been studied in a sample of children of different ages and times of implantation. Differences were found between cochlear implant users and children with normal hearing, in whom posture in different sensory conditions showed better performance when compared to the first group. Using regression curves related to both age and time of use of the cochlear implant, postural control showed a significant improvement with age and time of implant use.

      Explaining these findings under the laws of the closed-loop control system was proposed as a first step, in which there is a re-weighting of sensory input, having visual and somatosensory information serving a major role in maintaining accurate posture. Over time and with use of the implant, the central nervous system modifies the gain of the sensory input (visual, vestibular, and somatosensory) to achieve a definitive adaptation process.(8)

      Gait performance in implanted children was also assessed in conditions with the implant turned on and off.(9) Impaired gait (lower gait velocity) was found with the implant turned on. This suggests that hearing works as a “dual task” for them. However, when the sample was divided into two groups of children, those who were implanted before and after 3 years old, the gait performance in the earlier implanted children was similar to that of the children with normal hearing. These findings suggest that auditory input is not neutral in the progress of motor skills, and like in speech production, the interaction between auditory information and motor performance during the first years of childhood are crucial for a suitable neurodevelopment.

      Take Home

      The new findings seem to confirm the importance of less traumatic surgical procedures to avoid vestibular damage and implantation at the earliest stages of neurodevelopment are precise strategies to improve both speech and motor skills development in children with profound prelingual deafness.

      References

      1. Boggess WJ, Baker JE, Balkany TJ. Loss of residual hearing after cochlear implantation. Laryngoscope. 1989 Oct;99(10 Pt 1):1002-5.

      2. Kautzky M, Susani M, Hübsch P, Kürsten R, Zrunek M. Holmium: YAG laser surgery in obliterated cochleas: an experimental study in human cadaver temporal bones. Eur Arch Otorhinolaryngol. 1994;251(3):165-9.

      3. Klenzner T, Knapp FB, Schipper J, Raczkowsky J, Woern H, Kahrs LA, Werner M, Hering P. High precision cochleostomy by use of a pulsed CO2 laser - an experimental approach. Cochlear Implants Int. 2009;10 Suppl 1:58-62.

      4. Eze N, Jiang D, Fitzgerald, O'Connor A. Inner ear energy exposure while drilling a cochleostomy. Acta Otolaryngol. 2014 Nov;134(11):1109-13.

      5. Frounlund J, Harder H,Maki-Torkko E, Ledin T. Vestibular Function after Cochlear Implantation: A Comparison of Three Types of Electrodes.Otol Neurotol 2016 37(10)1535-1540.

      6. Wolter NE, Cushing SL,MadrigalLD,James Al,Campos J, Papsin BC,Gordon KA.Unilateral Hearing Loss Is Associated With Ipaired Balance in Children.: A PIlot Study. Otol Neurotol 2016.37(10) 1589-1595.

      7. Inoue A, Iwasaki S, Ushio M, Chihara Y, Fujimoto C, Egami N, Yamasoba T. Effect of Vestibular Dysfunction on the development of gross motorfunction in children with profound hearing loss. Audiol Neurotol 2013: 18(3) :143-151.

      8. Suarez H, Ferreira E, Alonso R, Arocena S, San Roman C,Herrera T,Lapilover V.Acta Otolaryngol. 2016; 136(4):344-350.

      9. Suarez H, Alonso R, Arocena S, Ferreira E, San Roman C, Suarez A, Lapilover V. Sensorymotor interaction in deaf children.Relationship between gait performance and hearing input during childhood assessed in prelingual cochlear implant users. Acta Otolaryngol.2016.15:1-6.

       

      Guest Author: Hamlet Suarez, MD

      Chairman, Laboratory of Otoneurology

      British Hospital, Biomedical Engineering Program

      Montevideo, Uruguay

      www.otoneurolab.com

       
      Hamlet Suarez, MD
      Slow Insertion of Cochlear Implant Electrodes
       

      Introduction

      Since preservation of residual hearing during cochlear implantation (CI) was first described in 1989(1), it has become clear that hearing preservation is possible in most cases (2,3) and that it can result in better CI outcomes(4,5). Over the last several years, slow electrode insertion speed has been evaluated as a surgical technique to optimize hearing preservation.

      What’s New

      Timed observations estimate that surgeons insert electrodes over a period of roughly 10 to 30 seconds(6). Slower insertions (30 seconds or more) have been associated with better hearing preservation as well as better vestibular function(7). Further, two mechanistic explanations for the traumatic effects of fast insertion were investigated with plastic models of the cochlea and support the notion that slower may be better:

      • Higher insertion speed increases insertion force(6), which increases electrode insertion trauma(8).

      • Higher insertion speed also causes increased intra-cochlear fluid pressure, which itself appears to be traumatic(9).

      • We should also note that stop-and-go insertion and surgeon tremor may cause intermittent increases in intra-cochlear fluid pressure(10).

      However, it is relevant to mention that plastic models, while useful in understanding certain mechanics of insertion, cannot account for many of the variables of human electrode insertion:

      • In plastic cochleae, cochleostomy size is fixed. In surgery, cochleostomy size is variable (e.g.: RWM linear incision vs. flap), resulting in differences in capacity for fluid egress/pressure relief.

      • In human cochleae, instantaneous pressure relief may also occur via the internal auditory canal, cochlear aqueduct, vestibular aqueduct, or mobile stapes footplate.

      • Other than fluid egress, plastic cochleae filled with fluid are incompressible systems. Conversely, human cochleae have compressible elements that may mitigate pressure peaks and trauma.

       

      Take Home

      Based on current research, electrode insertion should be slow and continuous, taking 30 seconds or more to complete. Using appropriate cochleostomies, insertion angles and electrode trajectories, along with slow-speed insertion, should minimize trauma and improve hearing preservation. Slow insertions have also been associated with less resistance and a higher rate of complete insertions.

       

      References

       

      1. Boggess WJ, Baker JE, Balkany TJ. Loss of residual hearing after cochlear implantation. Laryngoscope. 1989;99:1002-5.

      2. Hodges AV, Schloffman J, Balkany T. Conservation of residual hearing with cochlear implantation. Am J Otol. 1997 Mar;18(2):179-83.

      3. Balkany TJ, Connell SS, Hodges AV, Payne SL, Telischi FF, Eshraghi AA, Angeli SI, Germani R, Messiah S, Arheart KL. Conservation of residual acoustic hearing after cochlear implantation. Otol Neurotol. 2006 Dec;27(8):1083-8.

      4. Gifford, R., H., Dorman, M. F., Skarzynski, H., Lorens, A., Polak, M., et al. (2007). Cochlear implantation with hearing preservation yields significant benefit for speech recognition in complex listening environments. Ear and Hearing, 34(4), 413-425.

      5. Sheffield SW, Jahn K, Gifford RH. Preserved acoustic hearing in cochlear implantation improves speech perception. J Am Acad Audiol. 2015 Feb;26(2):145-54

      6. Kontorinis G, Lenarz T, Stover T, Paasche G. Impact of insertion speed of cochlear implant electrodes on the insertion forces. Otol Neurotol. 2011 32:565-570.

      7. Rajan GP1, Kontorinis G, Kuthubutheen J. The effects of insertion speed on inner ear function during cochlear implantation: a comparison study. Audiol Neurootol. 2013;18(1):17-22.

      8. Ishii T, Takayama M, Takahashi Y. Mechanical properties of human round window, basilar and Reissner's membranes. Acta Otolaryngol Suppl 1995;519:78-82.

      9. Todt I, Mittmann P, Ernst A. Intracochlear fluid pressure changes related to the insertional speed of a CI electrode. Biomed Res Int. (Online only: http://dx.doi.org/10.1155/2014/507241.

      10. Todt I, Ernst A, Mittmann P. Effects of Different Insertion Techniques of a Cochlear Implant Electrode on the Intracochlear Pressure. Audiol and Neurotol 2016;21:30-37.

       
      Vestibular Preservation in CI Surgery
       

      Introduction

      Improved surgical techniques, low-trauma electrodes, and the use of steroids can be effective in preserving residual hearing after cochlear implantation (ICIT CI Surgery Blog: 9/16; 8/16; 6/16; 3/16; 2/16; 1.1/16…). However, less attention has been given to preservation of vestibular function. This is understandable because from a clinical practice perspective, post-CI vestibular complaints are surprisingly uncommon; possibly due to the remarkable capacity for central vestibular compensation and adaptation.

      Although spontaneous complaints are few, when recipients are specifically questioned, post-CI vestibular symptoms have been reported to be as high as 75%(1). And as surgical indications expand and bilateral implantation becomes more common, preservation of vestibular function may take on an important clinical role. Can vestibular function be preserved by techniques used for hearing preservation?

      Buchman et al, using a hearing preservation surgical technique including bony cochleostomy, found that unilateral CI rarely results in significant adverse effects on the vestibular system and that postural stability actually improved post-implantation(2). Recent studies tend to validate those findings.

      What’s New

      Chen and colleagues from Zhengzhou University School of Medicine described vestibular function studies of severe-profoundly deaf CI recipients who were implanted using round window cochleostomies and a ‘standard’ technique(3). With this ‘standard’ technique, vestibular damage was frequently caused by implantation. Reduction in pre-operative caloric responses occurred in 93% of subjects and 40% lost VEMP waveforms. These results and similar previous studies(4-6) suggest that preservation of residual vestibular function may be less likely in CI recipients who do not undergo hearing preservation type surgery.

      In contrast, Tsukada and colleagues from the Shinshu University School of Medicine performed a similar study using hearing preservation techniques (7). Like Buchman, Tsukada et al report little or no additional loss of caloric or VEMP function with sensory-preservation surgery.

       

      Take Home

      These studies suggest that preservation of residual vestibular function may be more likely in patients who undergo cochlear implantation using sensory-preservation surgical techniques. And like hearing preservation, vestibular preservation is a desirable outcome of cochlear implantation.

       

       

      References

       

      1. Buchman CA, Joy J, Hodges A, Telischi FF, Balkany TJ. Vestibular effects of CI. Laryngoscope 2004;114:1–22.

      2. Steenerson RL, Cronin GW, Gary LB. Vertigo after cochlear implantation. Otol Neurotol 2001;22:842–843.

      3. Chen X, Chen X, Zhang F, & Qin Z. (2016) Influence of cochlear implantation on vestibular function, Acta Oto-Laryngologica, 136:7, 655-659.

      4. Melvin TA, Della Santina CC, Carey JP, Migliaccio AA. The effects of cochlear implantation on vestibular function. Otol Neurotol 2009;30:87–94.

      5. Krause E, Louza JP, Wechtenbruch J, Gürkov R. Influence of cochlear implantation on peripheral vestibular receptor function. Otolaryngol Head Neck Surg 2010;142:809–13.

      6. Licameli G, Zhou G, Kenna MA. Disturbance of vestibular function attributable to cochlear implantation in children. Laryngoscope 2009;119:740–5.

      7. Tsukada K, Moteki H, Fukuoka H, Iwasaki S, Usami S-I. Effects of EAS cochlear implantation surgery on vestibular function. Acta Oto-Laryngologica. 2013; 133: 1128–1132.

       
      Use of the Laser in Cochlear Implant Surgery
       

      Introduction

      In otology/neurotology, the LASER has been described for use in treatment of acoustic neuromas, cholesteatomas, and stapes surgery (1-4). A wide variety of LASERs exist for otologic use; however, the most commonly used are the carbon dioxide (CO2), potassium-titanyl phosphate (KTP), and argon LASERs. Each of these LASERs has their strengths and weaknesses with surgeons preferring one or the other based on cost, ease of use (i.e., flexible fiber vs. micromanipulator), wavelength, and interaction with tissue. What is less commonly discussed is use of the LASER in cochlear implant (CI) surgery.

      Use of a KTP laser in conjunction with fiberoptic endoscopy to remove bony obstruction of the inferior segment of the cochlea was first documented by Balkany (5) in 1990. Video of this procedure is available below.*

      Additional studies were performed by Kautzky et. Al., who attempted to recanalize the basal turn of a human cadaveric cochlea that was artificially obliterated (6). Klenzner et. Al. described the use of the CO2 laser for a high-precision cochleostomy in an experimental model; the goal of the study was to reduce the trauma to the cochlea during hearing preservation approaches in a contactless fashion. Fishman et. Al. studied the CO2 laser in 18 guinea pig models. The authors measured compound action potential (CAP) thresholds by acoustic tone pips and noted little change after creating the cochleostomy with the LASER (7). Cipolla et. Al. performed standard drill and CO2 laser cochleostomies on 30 cadaveric temporal bones (8). They felt that the operative times were similar between the 2 techniques. However, the LASER had an intracochlear sound level that was significantly lower than the drill (54.9 vs. 89.9 dB, P<0.001). Other authors have described a significant and marked energy transfer when allowing the drill to touch the endosteum (9). This is something that should not occur with the LASER, although the LASER can cause heat transfer to the perilymph of the scala tympani (8).

      What's New

      If one considers the CI surgery as a combination of standard mastoidectomy techniques followed by the principles of stapes surgery, then the LASER may be a tool that can be used to minimize intracochlear trauma. The CI team at the University of Cincinnati (UC) has used the CO2 laser for over 5 years, whether using a round window (RW) or cochleostomy approach, depending on the type of electrode and the anatomic constraints of the individual patient.

      While the UC CI team is in the midst of publishing our results, we have given 2 presentations at ACIA meetings discussing our results (manuscript in preparation) (10). We performed a retrospective chart review of patients undergoing hybrid CI from 2011-2014. The CO2 laser was used to ablate vasculature on the promontory and RW for meticulous mesotympanic hemostasis. All patients had slow insertion and intratympanic steroids as well as preoperative and postoperative systemic steroids. Comparisons of pre-and postoperative pure tone thresholds, AZBioQ, and CNC scores were made at 3 months and ≥1 year. Usage rates of electro-acoustic stimulation were documented. Nineteen ears underwent hybrid implantation. The mean age was 62 years. 53% of patients were male. Mean follow up was 17.3 months. At the time of first post-operative audiometric evaluation (mean 3.4 months), 79% of patients had low frequency hearing preservation. Eight of these have since been tested at a follow up date ≥1 year (mean 19.3 months) with a low frequency average of 59.8dB. Preoperative AZBIOQ was 48.7%, compared with 55.3% postoperatively. A significant improvement in CNC was detected pre- to post-op (27.3% to 52.4%; p=0.0049). 74% of patients in the study were still utilizing electro-acoustic stimulation at most recent follow up.

      Take Home

      Whether one uses a drill or a LASER, the goal is to minimize intracochlear trauma, entrance of blood or bone products (which can subsequently cause labyrinthitis and/or fibrosis and bone formation); these are important principles whether performing standard cochlear implantation or hearing preservation (soft surgery) techniques. While the use of the LASER may be a promising approach to open the cochlea and perform soft surgical techniques, I agree with Elsholz et. Al. in stating that there is a need for additional investigation in this area (11).

       

      *ICIT VIDEOS DEMONSRATING THIS TOPIC: https://cochlearimplanttraining.com/videolibrary/

      • Thomas Balkany, MD. Endoscopic Cochlear Implantation in Patients with FAO: 1988 Video of two patients with FAO undergoing cochlear implantation using 0.8 mm 0 degree Machida fiber-scope and KTP laser (3:55)

      • Ravi N. Samy, MD. Right CI: Use of CO2 Flexible Fiber Laser: Right CI: Use of CO2 flexible laser in preparation of cochlear implantation via round window (3:01)

       

      REFERENCES

      1. Smith, MFW, Lagger R, and Shinn JB. Carbon Dioxide Lasers in Managing Basal Skull Tumors. West J Med. 1982 Sep; 137(3): 229.

      2. Thedinger BS.Applications of the KTP laser in chronic ear surgery. Am J Otol. 1990 Mar;11(2):79-84.

      3. Sataloff J. Experimental use of laser in otosclerotic stapes. Arch Otolaryngol. 1967 Jun;85(6):614-6.

      4. Perkins RC. Laser stapedotomy for otosclerosis. Laryngoscope. 1980 Feb;90(2):228-40.

      5. Balkany TJ. Endoscopy of the Cochlea During Cochlear Implantation. Ann of Otol Rhinol Laryngol 1990;99:919-922.

      6. Kautzky M, Susani M, Hübsch P, Kürsten R, Zrunek M. Holmium: YAG laser surgery in obliterated cochleas: an experimental study in human cadaver temporal bones. Eur Arch Otorhinolaryngol. 1994;251(3):165-9.

      7. Klenzner T, Knapp FB, Schipper J, Raczkowsky J, Woern H, Kahrs LA, Werner M, Hering P. High precision cochleostomy by use of a pulsed CO2 laser - an experimental approach. Cochlear Implants Int. 2009;10 Suppl 1:58-62

      8. Fishman AJ, Moreno LE, Rivera A, Richter CP. CO(2) laser fiber soft cochleostomy: development of a technique using human temporal bones and a guinea pig model. Lasers Surg Med. 2010 Mar;42(3):245-56.

      9. Cipolla MJ, Iyer P, Dome C, Welling DB, Bush ML. Modification and comparison of minimally invasive cochleostomy techniques: A pilot study. Laryngoscope. 2012 May;122(5):1142-7.

      10. Eze N, Jiang D, Fitzgerald, O'Connor A. Inner ear energy exposure while drilling a cochleostomy. Acta Otolaryngol. 2014 Nov;134(11):1109-13.

      11. Redmann A, Stevens S, Altman A, Houston L, Hammer T, and Samy RN. Low frequency preservation and speech hearing performance following hybrid cochlear implantation with a modified soft surgical technique using the carbon dioxide laser. Presented at the ACIA meeting, 2016, in Toronto, Ontario, Canada (2016). Manuscript in preparation.

      12. Elsholz A, Böttcher A, Knecht R, Dalchow CV.Overview of Alternative Methods of Cochleostomy with Focus on Laser Ablative Techniques. Laryngorhinootologie. 2015 Jul;94(7):437-40. doi: 10.1055/s-0035-1548808. Epub 2015 Jun 30.

       
      Ravi N. Samy, MD
      Evolution of Cochlear Implant Electrodes: Straight vs. Pre-Curved
       

      Introduction

      Early intra-cochlear electrodes were simply straight, short wires. The House single-channel electrode was a somewhat variable length (around 4 mm) of copper wire with a flame-balled tip (1). Preserving hearing was not a priority for the anacusic or profoundly deaf patients implanted in the 1960s and 1970s and short electrodes seemed appropriate to the expectations of single channel implantation.

      Extra-cochlear electrodes were also in common use at that time. Douek et al (2) implemented a steel, flame-tipped electrode that was initially placed on the round window membrane in 1976. It was later placed on the promontory after surgical collapse of the tympanic membrane (tympano-cochleopexy) where it was held in place by spring-loading it to a hearing aid mold. Other unilateral extra-cochlear systems were used in a number of centers including Portmann (3) in Bordeaux and by Burian and Hochmaier (4) in Vienna.

      Banfai et al (5) in Cologne-Duren used a 16-channel extra-cochlear electrode nicknamed the Hedgehog. Anatomic studies allowed promontory surface projections of the scalae. Bone was thinned in the areas to be stimulated and a plate was wedged against the promontory with 16 metal projections in corresponding locations.

      As it became clear that extra-cochlear and single channel intra-cochlear devices provided limited benefit, the push was on to optimize multi-channel devices with intra-cochlear electrodes. Two outstanding electrode engineers, among others, who played a critical role in the evolution of CI electrodes deserve recognition for their work: Janusz Kuzma and (Melbourne, Valencia), Claude Jolly (Vienna).

      Multichannel electrodes were first used in the 1960s by House and Simmons (later abandoned). More successful prototypes were developed in the 1970s by Michelson and Schindler (San Francisco), Eddington (Salt Lake City), Chouard (Paris), the Hochmairs (Vienna), and Clark (Melbourne), et al.

      The most commonly used commercially available multi-channel electrodes of the 1980’s were straight, bulky, stiff, and traumatic (6). In comparison, early peri-modiolar electrodes of the 1980s were less traumatic and had the putative advantage of being close to ganglion cells, limiting current spread during bipolar stimulation. However, the industry has leaned to monopolar stimulation, largely to increase battery life, thereby increasing current spread and reducing some potential benefits of peri-modiolar electrodes. Straight, flexible, low-trauma electrodes came into common use in the 1990s.

      The current emphasis in electrode development is on reducing electrode insertion trauma. Doing so helps preserve residual hearing and improve CI outcomes (with and without electro-acoustic stimulation). The very short, very delicate hybrid electrodes developed by Gantz are the best example of low-trauma electrodes (7).

      Over the last decade, advanced imaging techniques have been used to estimate scalar location (S. tympani vs. S. vestibuli) in living subjects. It is generally thought that electrode location in S. vestibuli may be a surrogate for cochlear trauma and appears to correlate with poorer hearing outcomes and reduced hearing preservation (8,9).

      What’s New

      O’Connell, Hunter, Gifford, Rivas, Haynes, Noble and Wanna8 at Vanderbilt University recently compared outcomes using contemporaneous straight and peri-modiolar electrodes with identical processors from the same manufacturer.

      Scalar Place Outcomes

      In a retrospective sample of 56 implanted ears (20 straight, 36 peri-modiolar electrodes), imaging evidence of electrode transgression from ST into SV was noted in 10% of straight electrodes and in 53% of perimodiolar electrodes (p=0.002).

      Hearing Outcomes

      Hearing outcomes at one year were better for straight electrodes. CNC word scores were 55.4% for straight electrodes compared with 36.5% for perimodiolar electrodes (p = 0.005). AzBio sentence scores were 71.2% vs. 46.7% (p = 0.004).

      However, even when both types of electrodes were entirely within ST, sentence scores were somewhat higher for straight electrodes. This indicates that trauma or other factors unrelated to scalar transgression have not yet been explained and deserve further investigation.

       

      Take Home

      Electrode design has continuously evolved since the first CIs were implanted. The data suggests that the straight, thin, flexible electrodes used in this study may provide better hearing preservation and hearing outcomes than the perimodiolar electrodes used. Of course, this is not generalizable to all peri-modiolar and all thin-straight electrodes.

      Electrodes range from < 1 cm to 3 cm in length. The shortest may have the greatest chance for hearing preservation but may be less efficient without simultaneous acoustical stimulation. The longest may better access low frequency place, but may be somewhat more traumatic. Look for a variety of length options to become available, which may be most suitable for the amount of residual hearing and other factors. Parallel efforts to retain residual hearing include improved surgical techniques and the use of pharmaceuticals.

       

      References

      1. House WF, Urban J. Long term results of electrode implantation and electronic stimulation of the cochlea in man.Ann Otol Rhinol Laryngol.1973 82(4):504–517.

      2. Douek E, Fourcin AJ, Moore BCJ, Rosen S, et al. Clinical Aspects of Extra-cochlear Electrical Stimulation. Annals NY Acad Sci (2006) 405: 332-336.

      3. Portmann M, Cazals Y, Negrevergne M. Extra-cochlear Implants. Otolaryngol Clin N America. (Balkany TJ, ed.) (1986) 19: 307-312.

      4. Burian K, Hochmaier-Desoyer I, Eisenwort B. The Vienna Cochlear Implant Program. Otolaryngol Clin N America. (Balkany TJ, ed) (1986) 19: 313-328.

      5. Banfai P, Karczaq A, Kublik S, Luers P, Surth W. Extra-cochlear sixteen-channel electrode system. Otolaryngol Clin N America. (Balkany TJ, ed) (1986) 19: 371-408.

      6. Kennedy DW. Multichannel intracochlear electrodes: mechanism of insertion trauma. Laryngoscope 1987; 97:42-49.

      7. Gantz BJ, Turner C, Gfeller KE, Lowder MW. Preservation of hearing in cochlear implant surgery: advantages of combined electrical and acoustical speech processing. Laryngoscope 2005;115:796–802.

      8. O'Connell BP, Hunter JB, Gifford RH, Rivas AR, Haynes DS, Noble JH, Wanna GB. Electrode location and audiologic performance after cochlear implantation: a comparative study between Nucleus CI422 and CI512 electrode arrays. Otol and Neurotol 2016;37:1032-35.

      9. Boyer E, Karkas A, Attye A, et al. Scalar localization by cone-beam computed tomography of cochlear implant carriers: a comparative study between straight and periomodiolar precurved electrode arrays. Otol Neurotol 2015;36:422–9.

       
      Long CI Electrodes: Hearing Outcomes
       

      Introduction

      Very-long CI electrodes (28mm, 31 mm), elegantly flexible and minimally traumatic, are designed to be deeply inserted into the low-frequency areas of the upper cochlear turns. However, it is not yet clear whether this additional depth of insertion provides outcomes superior to standard-length electrodes (< 24 mm). This is important because reaching the upper turns comes at a potential cost.

      Very-long electrodes have previously been associated with greater loss of residual hearing and balance (1) as well as a higher rate of incomplete insertion (18%) than standard-length electrodes (2). (CI Surgeons Blog 12/1/15)

      What’s New

       

      Failure of complete insertion

      Daniele De Seta and colleagues of a research consortium led by Isabelle Moniere of the Groupe Hospitalier Pitié-Salpêtrière in Paris, reported that in a 5-year, prospective, multi-center study, failure of full insertion of very-long electrodes occurred in 12 of 38 (32%) implanted ears (3).

      De Seta et al also found that the size of the cochlea had no effect on failure of full insertion. “The size of the cochlea…was similar between the ears with a full insertion and the ears with a partial insertion.” “No significant difference in the size of the cochlea between ears with incomplete and complete insertions was found in our study (3).” This differs from prior studies suggesting that the high partial insertion with very-long electrodes is due to the variable size of the cochlea. Since the size of the cochlea did not appear to be the cause of incomplete insertion, other factors might be considered, including the additional length of the electrode.

      Loss of residual hearing

      Kisser et al of the University of Munich reported sub-total loss of residual hearing with 28 mm electrodes, concluding that the 28 mm electrode “does not allow for usable additional hearing at present (4).”  The authors recognize technical difficulties that may somewhat limit their study.

      Hearing not improved

      De Setta shows that the depth of insertion of very-long electrodes was not associated with better hearing outcomes. In considering only ears with full electrode insertion, but variable angular depth of insertion (510° to 880°), the authors found that deeper insertion into the apical region does not correlate with better hearing. “If we consider the ears with full insertion of the electrode array, despite a large variation of the angular depth of insertion, no correlation was found between this variable and the hearing performance.” 3In other words, “No correlation was found between the speech perception scores and the angular depth of insertion, both in quiet and in noise….(3)”  Nonetheless, it may be important to note that even the 510° insertions are deeper than most standard-electrode insertions.

       

      Take Home

      • In expert hands, incomplete insertion of very-long electrodes occurred in 18 - 32% of ears.

      • Deeper cochlear penetration with very-long electrodes added no hearing benefit in this study. (Angular depth is not the same as length. Depth depends on cochlear size and electrode trajectory).

      The De Seta study includes 38 subject ears, a notable accomplishment for a 5-year study. The findings reported are statistically significant. Nonetheless, as the authors point out, it is possible that larger studies may have different findings. It should also be noted that previous studies have found benefits of very-long electrodes. (5,6)

       

      References

      1. Nordfalk K F, Rasmussen KH, Bunne, M et al. Insertion Depth in Cochlear Implantation and Outcome in Residual Hearing and Vestibular Function. Ear and Hear 2015. Epub ahead of Print -

      2. Brito R, Alves T…Bento RF. Surgical complications in 550 consecutive cochlear implantations. Braz. J. Otorhinolaryngol. 78; 3: May/June 2012.

      3. De Seta D, Nguyen Y, Bonnard D, Ferrary E, Godey B, Bakhos D, Mondain M, Deguine O, Sterkers O, Bernardeschi D, Mosnier I. The Role of Electrode Placement in Bilateral Simultaneously Cochlear-Implanted Adult Patients. Otolaryngol. Head Neck Surg. (05/2016) E-Published before print: 0194599816645774.

      4. Kisser U, Wunsch J, Hempel JM, Adderson-Kisser C, Stelter K, Krause E, Muller J, Schrotzmair F. Residual hearing outcomes after cochlear implant surgery using Ultra-flexible 28-mm electrodes. Otol Neurotol, PAP 2016) doi: 10.1097/MAO.0000000000001089.

      5. Roy AT, Penninger RT, Pearl MS, Wuerfel W, Jiradejvong P, Carver C, Buechner A, Limb CJ. Deeper Cochlear Implant Electrode Insertion Angle Improves Detection of Musical Sound Quality Deterioration Related to Bass Frequency Removal. Otol Neurotol. 2016 Feb;v37(2):146-51.

      6. Hochmair I, Hochmair E, Nopp P, Waller M, Jolly C. Deep electrode insertion and sound coding in cochlear implants. Hear Res. 2015 Apr; 322:14-23.

       
      Do Current Guidelines Prevent Access to Cochlear Implantation?
       

      Background

      In the era of single channel cochlear implants, nothing less than bilateral profound deafness was an indication for surgery. But as CI performance improved, auditory guidelines for candidacy expanded. And as safety and efficacy of implantation were confirmed, young children and older adults were included. It has been anticipated that, consistent with improving outcomes, the candidate field would continue to expand.

      So it is not surprising that in clinical practice, hearing impaired people with conditions that once contraindicated implantation are now candidates. Some of these prior contraindications include (1):

      • Significant residual hearing

      • Cochlear dysplasia

      • Auditory neuropathy spectrum disorder

      • Pre-linguistically deaf adolescents and adults

      • Non-auditory developmental or cognitive delay

      • Single sided deafness

      Unfortunately, written guidelines for candidacy may not reflect best practices, which tend to respond quickly to evidence-based, peer-reviewed research. Too often, CI professionals must challenge regulatory and insurance authorities in the best interest of their patients. As a result, inappropriate guidelines and regulations tend to prevent access to CI for many candidates who could be expected to benefit. A special issue of Cochlear Implants International (ed., John Graham) addresses this concern (2).

      New Information

      Restricted access to CI may be especially important in children. Hanvey et al.(3) report evidence of harm being done to patients because “…guidelines may be interpreted as strict criteria whereby clinicians adhere to specific audiometric thresholds without accounting for the acceptable range of performance…or a child’s functional development.” Most would also agree that reliance on audiometric thresholds is inappropriate in the first place although threshold hearing remains the standard guideline for implantation in most regions.

      Prof. Paul Govaerts of the Eargroup and Antwerp University addresses this issue from the clinical as well as ethical perspectives. From the clinical perspective, Govaerts(4) correctly asserts that,

      “…CI selection must be highly individual, whereas the current criteria are general, not valid, not based on a wide consensus, and not up-to-date.”

       

      Factors that are specific to each candidate, such as cause and duration of hearing loss, age, motivation, family support, prior successful imbedding of children in Deaf cultures, availability of auditory-verbal therapy and socio-economic factors, are universally considered important by CI teams but ignored by governmental agencies and insurance companies (4,5). Further, today’s outcomes are significantly better than those of the previous decade (4). By the time new CI candidacy criteria achieve consensus approval by bureaucratic agencies, they are often out of date.

      From the ethical perspective, CI teams often face a moral dilemma pitting the obligation to act in the best interest of the patient against the restrictions imposed by strict criteria. Govaerts4 provides the following example:

      Although evidence has long demonstrated the value of CI in young children,

      “There are entire cohorts of babies who did not receive a CI at the necessary early age because of the administrative criteria of many countries. For the rest of their lives these children are doomed to a disability that is much greater than what should have been.”

      Take Home

      CI criteria may still have a role to play in training of new generations of CI specialists, general guidance for teams and in the clinical evaluation of new methods and technology. However, if strict criteria are used to deny services to appropriate candidates and primarily serve administrative or financial interests, the system must adapt or be abandoned.

      References

      1. Arnolder C, Lin VY Expanded selection criteria in adult cochlear implantation. Cochlear Implants Int. 2013. 14: S10-3.

      2. Cochlear Implants International Volume 17, Supplement 1, 2016

      3. Hanvey K, Ambler M, Maggs J, Wilson K. Criteria versus guidelines: Are we doing the best for our paediatric patients? Cochlear Implants Int. 2016. 17 Suppl 1: 78-82.

      4. Govaerts PJ. Expert opinion: Time to ban formal CI selection criteria? Cochlear Implants Int. 2016. 17 Suppl 1: 74-77.

      5. Blamey P, Atieres F, Baskent D, Bergeron F, et al. Factors affecting auditory performance of post-linguistically deaf adults using cochlear implants: an update with 2251 patients. Audiology and Neurotology 2012. 18(1): 36-47.

       
      Hearing Aids, Cochlear Implants and Dementia
       

      Background

      Presbycusis is associated with accelerated cognitive decline, dementia and depression. Affected individuals suffer difficulty communicating, social isolation, loss of autonomy and general psychological involution. Memory and concentration decline 30 – 40% faster in older adults with hearing loss than in those with normal hearing (1,2). Further, the risk of developing dementia increases proportionately with the amount of hearing loss.

       

      ·Mild loss

      2x risk of dementia

      ·Moderate loss

      3x risk

      ·Severe loss

      5x risk

      New Information

       

      Two new studies help connect the dots between presbycusis and dementia. In the first, data from an animal model of cognitive impairment suggest that hearing loss may result in age-related cognitive dysfunction. In the second, general mental health of hearing impaired older adults is shown to improve with the appropriate use of hearing aids or cochlear implants.

       

      So and colleagues (3) from The Catholic University of Korea (Seoul, Korea), recently suggested a causal relationship between hearing loss and cognitive impairmentusing standard mouse models of cognitive function. The experimental group, mice with NIHL, had poorer cognitive function after 6 months than normal hearing controls. Some basic questions, such as a possible direct effect of sound-deafening on performance and correlation of the degree of HL with cognition, leave room for further investigation. Although replication is necessary, this is (to our knowledge) the first study to support a causal relationship between HL and dementia.

      In another recent paper, Contrera and colleagues (4) from Frank Lin’s group at Johns Hopkins demonstrated improved generic (that is, not disease-specific) mental health quality of life in hearing impaired older adults after 12 months use of a hearing aid (for moderate HL) or CI (for severe – profound HL). CI users improved nearly twice as much as HA users, partly a reflection of lower baseline scores. The safety and utility of CI in older adults, up to 80 and 90 years of age, has been demonstrated (5).

       

      Take Home

       

      A somewhat nebulous relationship between HL and dementia has been widely accepted for some time. These new studies begin to support the notion that HL may be one cause of age related decline in cognitive function and that appropriate intervention with hearing aids or cochlear implants may be effective in the management of dementia.

       

      References

      1. Lin FR. Hearing loss and cognition among older adults in the United States. J Gerontol A Biol Sci Med Sci2011;66:1131–6.

      2. Lin FR, Yaffe K, Xia J, Xue QL, Harris TB, Purchase-Helzner E. Hearing loss and cognitive decline in older adults. JAMA Intern Med 2013;173:293–9.

      3. So YPMin JKHuerxidan S, Dong-Kee K,Sang WY, Shi NP. A causal relationship between hearing loss and cognitive impairment. Acta Oto-Laryngolgica. Epub ahead of print (2016). DOI: 10.3106/00016489.2015.1130857.

      4. Contrera KJ, Betz J, Lingsheng L, Blake CR et al. Quality of Life After Intervention With a Cochlear Implant or Hearing Aid. Laryngoscope e Pub before print DOI: 10.1002/lary.25848 (2016).

      5. Eshraghi AA, Rodriguez M, Balkany TJ. Cochlear implant surgery in patients more than seventy-nine years old. Laryngoscope (2009) 119:1180-1183.

       
      Preservation of Residual Hearing: Pharmaceutical Agents
       

      Background

      Electrode insertion trauma (EIT) is thought to be a primary cause of loss of residual hearing during cochlear implantation (CI). Over the past three decades, improved surgical techniques and electrode design have partially preserved residual hearing and improved CI outcomes in many recipients.

      Although EIT may cause loss of residual hearing through immediate tissue disruption and necrosis, histological studies suggest that the preponderance of damage results from secondary inflammation, fibrosis/osteogenesis, oxidative stress and apoptosis. In some cases, these programmed pathways may be blocked to varying extents by medications. Some of the pharmaceuticals currently under investigation for preservation of residual hearing in CI include:

      • Steroids

      • Neurotrophins

      • Anti-oxidants

      • Mannitol

      Dexamethasone (Dex) has anti-inflammatory and anti-apoptotic characteristics. For example, Dex can suppress inflammatory cytokines, interleukins and TNF-alpha, increases expression of anti-apoptosis genes and decreases expression of pro-apoptosis genes in the cochlea. A single dose of systemic and/or topical steroids is often given just prior to implantation and has also been delivered orally in a two-week clinical trial (1).

      Neuroprotective growth factors such as brain derived neural growth factor (BDNF), insulin-like growth factor (ILGF), hepatic growth factor (HGF) and neurotrophin-3 (NT3) have been used experimentally to enhance ganglion cell survival after cochlear implantation. Delivery methods include osmotic pumps (2) and drug eluting electrodes. Neurotrophins have also been delivered with gene therapy via viral vectors (3) and cell therapy in alginate microspheres (4).

      N-acetyl cysteine (NAC) is a free radical scavenger that replenishes glutathione and L-cysteine. NAC provides protection against hydroxyl radicals and lipid peroxidase and blocks the MAPK/JNK apoptotic pathway in the cochlea.

      Mannitol reduces oxidative stress by stabilizing blood flow, especially in ischemia-reperfusion injury that may result from EIT. It has been shown to protect hair cells from acoustic trauma, gentamicin toxicity and TNF alpha mediated hair cell loss.

      New Information

      Steroids

      Bas et al. in Prof Van De Water’s lab (5) at the University of Miami Ear Institute recently published an important paper showing that Dex, when delivered by a drug eluting electrode, protected guinea pig cochleas against loss of hair cells and other neural elements, loss of hearing, fibrosis and increasing electrical impedance. Responses were dose-dependent and optimal drug concentrations were established. By using drug eluting electrodes, the delivery of Dex was continued for 3 months.

      The Van De Water electrode elutes Dex directly from the silastic carrier providing a possible advantage over other electrodes that utilize applied coatings. In such electrodes, applied coatings are eluted along with Dex and may tend to cause an inflammatory response in some cases.

      Growth Factors

      Kikkawa et al. (6) of Prof. Ito’s laboratory at Kyoto University have recently reported a hydrogel-coated guinea pig electrode that releases insulin-like growth factor (IGF) and hepatocyte growth factor (HGF). Loss of hearing (increased ABR threshold) was reduced by IGF and HGF eluting electrodes but histological changes were not affected. Hydrogel coating of CI electrodes may also reduce frictional forces during insertion.

      Polypyrrole (Ppy) coatings have also been used to deliver neurotrophins from CI electrodes in guinea pigs. Ppy is an electrical conductor and is eluted from electrodes during stimulation. In these experiments, reported by Richardson et al. (7) of Prof. O’Leary’s group at Melbourne University, NT3 enhanced spiral ganglion cell counts in ears that received electrical stimulation.

      Combination Therapy

      Several studies have demonstrated that the reactive oxygen species scavenger L-NAC, the osmotic regulator mannitol, and dexamethasone all have a protective effect after electrode insertion trauma. Each of these protective molecules has an independent mechanism of action that occurs at a different locus in the inflammatory/apoptotic cascade. Eshraghi et al (8) at the University of Miami Ear Institute initiated EIT in rats then explanted and cultured the organs of Corti in solutions containing graded concentrations of each molecule to identify effective dosage. Dose-response curves were developed to determine the drug concentration required to achieve 50% protection of HCs in vitro by each drug. A cocktail containing the three molecules was then evaluated in organotypic cultures. The combination of the three agents was 96% protective in vitro.

      Take Home

      Clinical studies have suggested that improved surgical techniques and less traumatic electrodes can reduce EIT and enhance preservation of residual hearing. The next stage in hearing preservation may be expanded use of pharmaceutical agents. Steroids have shown promise in clinical and laboratory settings while neurotrophins, antioxidants, and mannitol have shown promise in the laboratory.

      References

      1. Sweeney AD, Carlson ML, Zuniga MG, Bennett ML et al. Impact of Perioperative Oral Steroid Use on Low-frequency. Otology & Neurotology (2015) 36:1480–1485.

      2. Sly DJ, Hampson AJ, Minter RL…O'Leary SJ: Brain-derived neurotrophic factor modulates auditory function in the hearing cochlea. J Assoc Res Otolaryngol 2012, 13:1–16.

      3. Wang H, Murphy R, Taaffe D, Yin S, Xia L, et al. Efficient cochlear gene transfection in guinea-pigs with adeno-associated viral vectors by partial digestion of round window membrane. Gene Ther 2012, 19:255–263.

      4. Gillespie LN, Zania MP, Shepherd RK. Cell-based neurotrophin treatment supports long-term auditory neuron survival in the deaf guinea pig. J. Controlled Release. (2015) 198; 26 – 34.

      5. Bas, E, Bohorquez, J…Van De Water, TR, et al. Electrode array-eluted dexamethasone protects against electrode insertion trauma induced hearing and hair cell losses, damage to neural elements, increases in impedance and fibrosis: A dose response study. Hearing Research (2016), doi: 10.1016/j.heares.2016.02.003.

      6. Kikkawa YS, Nakagawa T, Ying L…Ito J. et al. Growth factor-eluting cochlear implant electrode: impact on residual auditory function, insertional trauma and fibrosis. Journal of Translational Medicine 2014, 12:280.

      7. Richardson RT, Wise AK, Thompson BC…O’Leary SJ et al. Polypyrrole-coated electrodes for the delivery of charge and neurotrophins to cochlear neurons. Biomaterials(2009) 30; 2614–2624.

      8. Eshraghi AA, Roell J…Van De Water, et al. A novel combination of drug therapy to protect residual hearing post cochlear implant surgery. Acta Otolaryngol (2016). http://dx.doi.org/10.3109/00016489.2015.1134809.