Adkins, Weston J.

Intraoperative electrocochleography (ECOG) is performed using a single low-frequency acoustic stimulus (e.g., 500 Hz) to monitor cochlear microphonics (CM) during cochlear implant (CI) electrode insertion. A decrease in CM amplitude is commonly associated with cochlear trauma and is used to guide electrode placement. However, advancement of the recording electrode beyond the sites of CM generation can also lead to a decrease in CM amplitude and is sometimes interpreted as cochlear trauma, resulting in unnecessary electrode manipulation and increased risk of cochlear trauma during CI electrode placement. In the present study, multi-frequency ECOG was used to monitor CM during CI electrode placement. The intraoperative CM tracings were compared with electrode scan measurements, where CM was measured for each of the intracochlear electrodes. Comparison between the peak CM amplitude measured during electrode placement and electrode scan measurements was used to differentiate between different mechanisms for decrease in CM amplitude during CI electrode insertion. Analysis of the data shows that both multi-frequency electrocochleography and electrode scan could potentially be used to differentiate between different mechanisms for decreasing CM amplitude and providing appropriate feedback to the surgeon during CI electrode placement.

Objective: Describe the first case of cochlear implantation (CI) for auditory rehabilitation of a patient with craniometaphyseal dysplasia (CMD) and progressive mixed hearing loss. Patients: A 65-year-old woman with known autosomal dominant CMD presented with progressive mixed hearing loss and declining benefit from conventional hearing aids. Computed tomography and magnetic resonance imaging revealed hyperostosis of the entire craniofacial skeleton. Hearing evaluation demonstrated pure-tone thresholds in the profound range bilaterally by air conduction, and bone conduction thresholds that matched aided thresholds for her left ear, though testing was somewhat limited by inability to mask at high air-conduction thresholds. CI candidacy testing confirmed poor word and sentence scores in the right ear. Intervention: Due to the inability to access the cochlea via a conventional mastoidectomy and facial recess approach, cochlear implantation via a postauricular subtotal petrosectomy approach with ear canal overclosure was performed. Main Outcome Measures: Post-implantation word and sentence testing. Results: Despite extensive internal auditory canal stenosis, the patient demonstrated excellent early speech understanding results 5 weeks after device activation. Postimplantation audiologic evaluation showed thresholds between 20 and 30 dB HL from 250 to 6000 Hz. Word and sentence testing scores were 76% Consonant-nucleus-consonant in quiet (up from 2% preoperatively) and 77% AzBio sentences in quiet (up from 10% preoperatively). Conclusion: This report describes the first description of CI for CMD. Despite the extensive radiologic abnormalities, the patient has demonstrated excellent benefit from implantation. Further study of rare temporal bone dysplasias, such as CMD, is critical to better characterize the progression of otologic disease and determine optimal treatment.