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

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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
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9. ipolla 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.

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