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Received Oct 18, 2017; Accepted Mar 8, 2018
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1. Introduction
Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of disorders affecting the peripheral nervous system. The disease can manifest in profound SNHL, hypothesized to result from disruption of synchronous activity of the cochlear nerve. Given that CMT affects the retrocochlear auditory pathway, there have been theoretical concerns that CI is incapable of providing meaningful auditory stimulation. Two previous cases of CI in patients with CMT have been described in the world literature; thus, the role of cochlear implants in auditory rehabilitation of CMT-associated SNHL is poorly defined [1, 2]. We present a patient with CMT-associated deafness successfully treated with cochlear implantation.
2. Case Presentation
A 70-year-old male with CMT was referred for evaluation of progressive asymmetric SNHL and reported a 15-year duration of deafness involving the left ear. He was initially a bilateral hearing aid user but subsequently stopped using his hearing aid in the left ear several years prior due to experiencing progressive audiometric decline. Audiometric testing confirmed profound SNHL in the left ear, while the right ear exhibited moderate-to-severe SNHL. Information regarding the subtype of his CMT is unavailable at our tertiary care facility; prior workup was performed at another institution.
Left-sided cochlear implantation was performed using a conventional length lateral wall electrode. The electrodes were introduced without resistance, and a full insertion was achieved using the MED-EL™ Synchrony Flex® 28 cochlear implant. Intraoperative device testing found normal impedance levels throughout the array; however, electrically evoked auditory potentials were absent on all electrodes. Upon initial activation 3 weeks after surgery, the patient reported excellent access to sound in the cochlear implant-only condition. He has made good progress at each subsequent visit; speech perception testing after seven months showed improvement from 0% preoperatively to 32%...