Patterns of Extended High-frequency Hearing Loss Following Stapes Surgery.

OBJECTIVE: Thresholds in the extended high-frequency (EHF) range (> 8 kHz) often worsen after otherwise successful stapedectomy. The aims of this study were to document the prevalence of hearing loss from 0.25 to 16 kHz after stapedectomy and the relative rates of transient and permanent EHF hearing loss. STUDY DESIGN: Prospective, observational, longitudinal. SETTING: Tertiary referral center. PATIENTS: Thirty-nine patients who underwent 44 primary or revision stapes surgeries. INTERVENTION: Hearing thresholds were measured at 0.25 to 16 kHz preoperatively, and at approximately 1 week, 1, 3, 6, and 12 months postoperatively. MAIN OUTCOME MEASURES: Average threshold changes in bands of frequencies (0.25-1, 2-8, 9-11.2, 12.5-16 kHz) and the percentage of patients with a change in the highest frequency at which a hearing threshold could be measured were evaluated at each assessment. RESULTS: A mean hearing loss was documented in the EHF range at all postoperative assessments. There was a decrease in the highest frequency at which a hearing threshold was measureable in 77% of patients at the first postoperative assessment, and despite some improvement over time, in 50% of patients 12 months postoperatively. CONCLUSION: There is a significant incidence of EHF loss after stapedectomy. Although partial recovery often occurs, more than half of patients retain an EHF hearing loss 12 months postoperatively. As hearing loss in the EHF range is more common than loss at 4 kHz, EHF measurements may be a more sensitive model to compare surgical factors and evaluate pharmacologic interventions.

Patterns of hearing loss following retrosigmoid excision of unilateral vestibular schwannoma.

Objectives To determine the pattern of auditory responses, time-course of hearing deterioration, and possible site of lesion following retrosigmoid excision of unilateral vestibular schwannomas. Design Prospective, nonrandomized, observational pilot study. Setting Tertiary referral medical center. Main outcome measures Preoperative and postoperative pure-tone and speech audiometry, auditory brainstem response testing, and distortion product otoacoustic emissions were performed in 20 patients. Testing was conducted every 24 hours for the duration of hospitalization. Transtympanic electrocochleography was performed if delayed deterioration of auditory responses was documented. Results Of the 20 patients, 7 had no discernible cochlear nerve at the end of the procedure. Of the 13 patients with an intact nerve, 6 retained hearing, 3 with evidence of reduced neural function. Of the 7 who lost hearing despite an intact nerve, 5 lost at least cochlear and possibly also neural function, and 1 had reduced neural function but retained cochlear function. There were two examples of delayed deterioration of cochlear nerve responses. Conclusions Hearing loss following retrosigmoid removal of vestibular schwannomas most often involves loss of at least cochlear function, possibly in addition to neural damage. In a smaller number of cases anacusis or hearing deterioration can be attributed to purely neural trauma.