ICIT Blog

Preventing Electrode Tip Fold-Over

Thomas Balkany, MD

8.28.17

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.

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The American Cochlear Implant (ACI) Alliance

The Institute for Cochlear Implant Training

7.13.17

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/

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Audiologic Management of CI Patients has become Increasingly Complex

Terry Zwolan, Ph.D.

7/1/2017

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.

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Delayed Hearing Loss after Hearing Conservation Surgery

Thomas J. Balkany, MD

6.1.17

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.

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Advanced Audiology CI Course (AAC)

The Institute for Cochlear Implant Training

May-July 2017

CochlearImplantTrainingAAC.com

Designed to challenge both developing and practicing 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

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CI OUTCOMES: THE IMPACT OF SPIRAL GANGLION SURVIVAL

Thomas J. Balkany, MD

3.7.17

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.

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Development and Validation of the Cochlear Implant Surgical Competency Assessment Instrument

Thomas Balkany, Kaming Lo, Howard Francis, Simon Angeli, Michael Novak, William Luxford, Rodney Lusk, and Heather Strader

2.14.17

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

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Vestibular Function and Development of Motor Skills in Implanted Children

Guest Author: Hamlet Suarez, MD

1.2.17

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 hearing1-4 and have recently been proposed for preserving vestibular function. (CI Surgery Blog 12.5.16).

Also, measurements of vestibular function5-7, 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?

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Vestibular Preservation in CI Surgery

Thomas J. Balkany, MD

12.5.16

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.

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Use of the Laser in Cochlear Implant Surgery

Guest Author: Ravi N. Samy, MD

11.1.16

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 Balkany5 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

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Slow Insertion of Cochlear Implant Electrodes

Thomas J. Balkany, MD

9.13.16

Introduction

Since preservation of residual hearing during cochlear implantation (CI) was first described in 19891, it has become clear that hearing preservation is possible in most cases2,3 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.

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Evolution of Cochlear Implant Electrodes: Straight vs. Pre-Curved

Thomas J. Balkany, MD

8.15.16

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 al2 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 Portmann3 in Bordeaux and by Burian and Hochmaier4 in Vienna.

Banfai et al5 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

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Long CI Electrodes: Hearing Outcomes

Thomas J. Balkany, MD

6.5.16

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 balance1 as well as a higher rate of incomplete insertion (18%) than standard-length electrodes.2 (CI Surgeons Blog 12/1/15)

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Do Current Guidelines Prevent Access to Cochlear Implantation?

Thomas J. Balkany, MD

5.1.16

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.

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Hearing Aids, Cochlear Implants and Dementia

Thomas J. Balkany, MD

4.1.16

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 hearing1,2. 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

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Preservation of Residual Hearing: Pharmaceutical Agents

Thomas J. Balkany, MD

3.1.16

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

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RW Cochleostomy: A Cause of Progressive Hearing Loss?

Thomas J. Balkany, MD

2.1.16

Introduction

Up to one-third of recipients who retain residual hearing after CI have progressive low-frequency loss in the weeks or months after surgery.1,2

One common theory is that following CI electrode insertion, intra-scalar histiocytic and giant-cell infiltration (foreign body reaction), fibrosis and osteoneogenesis lead to the progressive loss.3,4 These inflammatory reactions may destroy residual neural elements or interfere with the fluid-pressure wave as well as basilar membrane vibration. But are intra-cochlear factors the only causes of progressive loss and does the location of the cochleostomy make a difference?

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Spiral Ganglion Cell Survival and CI Performance

Thomas J. Balkany, MD

1.1.16

Background

The key neural elements that are stimulated by cochlear implants (CI) are spiral ganglion cells (SGC). So it would seem logical that the more SGCs that survive, the better CI performance would be. Nonetheless, histopathologic studies have suggested that SGC survival rates do not correlate with CI performance. 1,2

However, prior temporal bone studies could not control for variables that might affect performance (age, cause of deafness, degree of hearing loss, duration of deafness, cognitive ability, etc.) Failure to control these variables cast some doubt on the validity of the findings above.

In short, the best data available over the past 25 years indicated that SGC survival did not correlate with CI performance, but those studies created an intuitive dissonance. In order to settle the issue, the critical variables would need to be controlled.

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Long Cochlear Implant Electrodes: Incomplete insertion, loss of residual hearing and balance

Thomas J. Balkany, MD

12.1.15

Background

Preservation of residual hearing has been a goal of CI surgery since it was first reported in 1989.1 It is an indication of good surgical technique and may result in enhanced speech perception in conventional2 and hybrid devices.3 Very-long electrodes (> 28 mm) have been used successfully for over two decades, but continue to be debated due to anecdotal inferences of loss of residual hearing and vestibular function, as well as a high incidence of insertion failure.

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Neural Plasticity and Age of Implantation

Thomas J. Balkany, MD

11.1.15

Background

In early stages of development, peripheral stimulation helps organize the sensory cortex, a process commonly referred to as neural plasticity. Neural plasticity may be best thought of as continuous reorganization throughout early life in which neural pathways are formed, but abandoned if not frequently used, in favor of other more active pathways.

In the auditory and visual systems, sensory deprivation during CNS development causes deficient organization, or detrimental reorganization of the cortex that may lead to permanent deficits.1 For example, in amblyopia (“lazy eye”), affecting about 2% of children, one eye is less functional than the other. If untreated, the visual cortex will “ignore” the less-coherent signals from the lazy eye and its neural pathways will degenerate, leading to blindness of that eye.

The central auditory system likewise undergoes sensory-deprivation-based detrimental reorganization in the event of peripheral deafness. In the absence of peripheral stimuli, the auditory cortex can be subsumed by the more active processes of the visual system, especially in signers. This cross-modal adaptation has been associated with poor outcomes when cochlear implantation is delayed.2 Although electrical stimulation with cochlear implants can establish central auditory pathways and diminish takeover by the visual system early in development, after 5 years of age, restitution of the auditory cortex may be minimal.3,4

Clinical experience has demonstrated the value of cochlear implantation prior to the age of 18 months and many feel that the ideal age is less than 12 months. Controlled studies confirm the time-sensitive nature of successful implantation. Based on ABR findings, Sharma, Dorman and Spahr demonstrated that progressively worse CI outcomes occur in prelinguistically deaf children who had delayed implantation.

  • Ninety-six percent (96%) of early implanted (age less than 3.5 years) children had normal P1 latencies. Only 5% of late implanted children (age greater than 7 years) had normal P1 latencies.5

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Effects of CI Electrode Insertion on Tinnitus

Thomas J. Balkany, MD

10.1.15

      Introduction

      Over the past three decades, several papers have demonstrated positive as well as negative effects of cochlear implantation (CI) on tinnitus.1-6

        ·Pre-operative tinnitus in CI candidates has been estimated at 65 – 100%.1, 2

        ·The rate of tinnitus improvement following CI ranges from 50 – 90%.4,5

        ·Tinnitus may be generated or made worse by CI in 0 – 28% of recipients.5, 6

      Theoretical mechanisms of CI effects on tinnitus include electrical stimulation and electrode insertion trauma (EIT). Electrical effects may reduce tinnitus by masking (creating an auditory percept that makes tinnitus inaudible), electrical suppression (directly altering the generation or neural transmission of the tinnitus signal) or by other mechanisms. EIT may cause increasing tinnitus due to neural or metabolic organelle damage that may cause abnormal signal generation. The following discussion addresses a series of patients in whom traumatic, scala transgressing insertion exacerbated tinnitus in comparison to another cohort in whom non-scala transgressing electrodes did not.

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High Rate of Migration/Partial Extrusion of Straight Cochlear Implant Electrodes

Thomas J. Balkany, MD

9.1.15

Background

Cochlear implant (CI) electrode migration is generally considered to be very uncommon, the subject of few clinical reports and often not considered when discussing CI complications with patients. However, partial electrode extrusion from the cochlea, enough to reduce function and cause aversive stimuli, may not be so unusual.

Rivas et al.1 described electrode migration as an important cause of cochlear reimplantation, second only to device failure at Hopkins. And Connell et al.2 reported a ten year period during which the United States Food and Drug Administration MAUDE database3 showed 151 reported instances of electrode extrusion (presumably underestimated due to the voluntary nature of reporting and the tendency to report only major extrusions).

Electrode extrusions are thought to have been more common in the generation of stiff, straight electrodes some two decades ago. To reduce the rate of electrode migration at that time, Cohen and Kuzma introduced a titanium clip that attached the electrode cable to the incus bridge (buttress)4 and Balkany and Telischi described the split bridge technique (a slot in the incus bridge) to fixate the cable in the same location.5 Both were effective in reducing electrode extrusion.6 However, the advent of pre-curved electrodes and more flexible cables reduced the tendency for electrode migration.

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Adaptive Cochleostomy

Thomas J. Balkany, MD

8.1.15

Background

Adaptive cochleostomy is the concept that a single type of cochleostomy is not ideal in all cases. Rather, the type of cochleostomy used should be selected based on the anatomy of the patient and the physical characteristics of the electrode to be inserted. In short, the cochleostomy should be adapted to the patient’s anatomy and the electrode used. Cochleostomy is used here to mean an enduring opening into the cochlea through which an electrode is inserted.

Advocates of round window membrane (RWM), extended RWM and bony cochleostomy approaches have claimed that their preferred technique is best. Support for each is provided in the literature.1-4 RWM insertion may minimize drill trauma, prevent bone dust and blood from entering the scala and reduce leakage of perilymph; extended RWM cochleostomy may provide a more favorable insertion trajectory when the RWM is angled too inferiorly; and bony cochleostomy allows better electrode alignment with the axis of the scalar lumen, especially important when inserting larger, stiffer or pre-curved electrodes.1 However, the one-size-fits-all arguments do not take into account common variations in patient anatomy and electrode configuration.

We initially presented the concept of Adaptive Cochleostomy at CI2012 in Baltimore5, proposing that no single method of cochleostomy was ideal in all cases. Shapira et al.6 had already demonstrated a normal variation in angulation of the RWM of 27 – 65°. RWM insertion in the case of angulation >45° (13% of patients) can result in modiolar trauma, insertion into the vestibule and electrode transposition into S. vestibuli. In such cases, bony cochleostomy is preferred.

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Spotlight: Institute for Cochlear Implant Training

ICIT

7/15/15

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Hyaluronic Acid and Hearing Preservation

Thomas J. Balkany, MD

7/1/15

Background

Preserving hearing after CI is a notable accomplishment. Although current studies suggest that CI outcomes may not be improved by hearing preservation (unless there is aidable hearing, especially speech recognition), there is evidence that the electrical dynamic range is larger when some hearing is preserved, which could be advantageous.1 Current methods of preserving residual hearing after CI include surgical technique, electrode design and the use of pharmaceutical agents.

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Inferior Cochlear Vein and Cochleostomy

Thomas J. Balkany, MD

6.1.15

Background

Cochleostomy is used here to mean an enduring opening into the cochlea through which a CI electrode is inserted. There are currently three leading categories of cochleostomy:

  • The original round window cochleostomy used with short, single channel implants by Wm. House and currently used with certain electrodes to conserve residual hearing,
  • Traditional bony cochleostomy, suggested by Graeme Clark to avoid misdirection of long multichannel electrodes by the crista fenestra,
  • Extended RW cochleostomy, consisting of extension of the RW by drilling labyrinthine bone antero-inferiorly in cases where the RWM is too small or angled too inferiorly to use effectively.

Helge Rask-Andersen and his colleagues at Uppsala University continue their remarkable work on the anatomy of the hook portion of the cochlea that is relevant to hearing conservation during cochlear implantation. In their detailed description of the hook region in 2014, they conclude that there may be anatomic reasons to prefer RW insertions in hearing conservation cases.1

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The Impact of Maturational Changes in Cochlear Position on Cochlear Implantation

Thomas J. Balkany, MD

5.1.15

Background

Three dimensional CT imaging provides good data regarding the positional changes in normal temporal bone development. Attention has been focused on the position of the basal turn in relation to other structures of the temporal bone. The following studies demonstrate that such changes occur rapidly between birth and 4 years of age and then may occur slowly until adulthood with a possible bump during puberty.

McRackan et al (2012) found age-related variation between adults and children in the orientation of the facial recess to the round window membrane (RWM). 1 Children had greater angulation than adults averaging 6.2°(p=0.01) between adults and children. Thus surgeons can expect a narrower view of the RWM in children and may find slightly more difficulty in electrode insertion. The authors also showed that maturation of the EAC over time simplifies the approach to the facial recess and RWM. The angle between the facial recess and EAC is more acute (tighter) in young children. This supports the findings of Lloyd et al (2010) who showed that the axis of the inferior segment of the basal turn becomes more parallel to the axis of the trans-mastoid approach angle over time.2

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Deficient Cochlear Nerve

Thomas J. Balkany, MD

4.1.15

The clinical term cochlear nerve deficiency has been established in the otologic literature to indicate a small or absent cochlear nerve on MR imaging. To the best of my knowledge it was first described by the Antwerp cochlear implant group in 1997.1

More recently, Buchman, Adunka and colleagues at UNC have shown that cochlear nerve deficiency (CND) is more common than previously recognized in CI candidates. CND may account for up to 20% of those with OAE/SP/ABR indications of auditory neuropathy spectrum disorder.2,3,4

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