Best practices for hearing preservation in cochlear implantation

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Cochlear implants that have electrodes designed without wire perform better than those with wires for long-term hearing preservation, reports a first-of-its-kind study which also determined that the best surgical approach for cochlear implant procedures did not involve drilling into the bone around the ear.The results may transform how doctors approach cochlear implant procedures to give patients the best possible outcomes.

Cochlear implants help preserve hearing in patients with nerve deafness who cannot benefit from hearing aids. They are surgically placed in the inner ear to convert sound waves into electrical signals that stimulate the auditory nerve to provide hearing.

“This is the largest clinical study done in the world on conventional electrodes and will have major implications for doctors and their patients who need their long-term hearing restored,” said the study’s lead investigator, Dr George Wanna, site chair, department of otolaryngology-head and neck surgery at New York Eye and Ear Infirmary of Mount Sinai (NYEE) and Mount Sinai Beth Israel; chief, division of otology-neurotology and director of the Centre for Hearing and Balance and Ear Institute at Mount Sinai Health System.

“This study is a breakthrough for patients with hearing loss, and improvements in practice and techniques will allow them to enjoy many hearing benefits such as music enjoyment, listening in complex environments, and sound localisation.”

Wanna and a team of researchers from Vanderbilt University examined roughly 230 patients with every type of cochlear implant, including three US Food and Drug Administration (FDA)-approved implants that use different types of electrodes to stimulate the auditory nerve. They found that electrodes designed with no wire (called lateral wall electrodes) performed the best in maintaining residual hearing in the inner ear, compared to electrodes made with wire. More specifically, the non-wire electrodes were less traumatic, causing less injury and minimizing fractures inside the inner ear. The study found that the actual brand of the electrode did not make a difference; the presence or absence of wire was the only distinguishing factor.

Wanna and the researchers also looked at the impact of two major surgical approaches used to insert the electrodes in the inner ear: “round window” (where surgeons open the membrane without bone removal or drilling in the inner ear) and “cochleostomy” (which requires drilling into the bone to get inside the inner ear). They reported that patients who had the round window approach had a much better chance of keeping their residual hearing in the long term.

“The cochleostomy approach causes fibrosis and scarring, leading to hearing loss over time,” said Wanna. “Our results also revealed that using oral steroids also helped in the long term to preserve hearing by preventing inflammation.” “We hope the findings will help surgeons choose the best implants and approaches for their patients,” said Wanna. “This is an exciting time in this field, and the advancement in hearing technology and continued improvements in techniques and outcomes will benefit patients and their families.”

Abstract
Objectives/Hypothesis: The aims of this study were to investigate short- and long-term rates of hearing preservation after cochlear implantation and identify factors that impact hearing preservation.
Study Design: Retrospective review.
Methods: Patients undergoing cochlear implantation with conventional-length electrodes and air-conduction thresholds ≤80 dB HL at 250 Hz preoperatively were included. Hearing preservation was defined as air-conduction thresholds ≤80 dB HL at 250 Hz.
Results: The sample included 196 patients (225 implants). Overall, the rate of short-term hearing preservation was 38% (84/225), with 18% (33/188) of patients preserving hearing long term. Multivariate analysis showed better preoperative hearing was predictive of hearing preservation at short (odds ratio [OR]: 0.93, 95% confidence interval [CI]: 0.91-0.95, P < .001) and long-term follow-up (OR: 0.94, 95% CI: 0.91-0.97, P < .001). Lateral wall electrodes and mid-scala electrodes had 3.4 (95% CI: 1.4-8.6, P = .009) and 5.6-times (95% CI: 1.8-17.3, P = .003) higher odds of hearing preservation than perimodiolar arrays at short-term follow-up, respectively. Long-term data revealed better hearing preservation for lateral wall (OR: 7.6, 95% CI: 1.6-36.1, P = .01), but not mid-scala (OR: 3.1, 95% CI: 0.4-23.1, P = .28), when compared to perimodiolar electrodes. Round window/extended round window (RW/ERW) approaches were associated with higher rates of long-term hearing preservation (21%) than cochleostomy approaches (0%) (P = 0.002) on univariate analysis.
Conclusions: Better preoperative residual hearing, lateral wall electrodes, and RW/ERW approaches are predictive of higher rates of long-term functional hearing preservation.

Authors
George B Wanna, Brendan P O’Connell, David O Francis, Rene H Gifford, Jacob B Hunter, Jourdan T Holder, Marc L Bennett, Alejandro Rivas, Robert F Labadie, David S Haynes

Mount Sinai Hospital/Mount Sinai School of Medicine material
The Laryngoscope abstract


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