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.

MRI Inner Ear Imaging and Tone Burst Electrocochleography in the Diagnosis of Ménière's Disease.

OBJECTIVE: To compare the sensitivity of gadolinium MRI inner imaging with tone burst electrocochleography (EcochG) for diagnosing endolymphatic hydrops. STUDY DESIGN: A prospective study on patients who were to have an MRI scan to exclude retrocochlear pathology. SETTING: Tertiary care center. PATIENTS: One hundred and two patients: 57 patients with Possible, Probable, or Definite Ménière's Disease, 25 with asymmetrical hearing loss, 18 with sudden sensorineural hearing loss, and 2 with unilateral tinnitus had additional MRI inner ear imaging and click and tone burst stimulus EcochG testing. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: To compare the sensitivity of the two techniques. RESULTS: In 30 patients with symptom-based Definite Ménière's Disease, tone burst EcochG was positive in 25 (83%) and the click EcochG was positive in 9/30 (30%), and gadolinium MRI imaging diagnosed hydrops in 14 (47%). A positive result for either MRI imaging or tone burst EcochG was seen in 26 patients (87%). In 14 subjects with symptom-based Probable Ménière's Disease, 10 (71%) had either a positive EcochG or MRI. In 13 with Possible Ménière's Disease, four (31%) had a positive EcochG or MRI. CONCLUSION: This study confirms the greatly enhanced diagnostic sensitivity of tone burst EcochG over click response in diagnosing endolymphatic hydrops in Ménière's disease. Even though adequate MRI imaging was achieved in 90%, tone burst EcochG was a more sensitive test.

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.