[Assessment of cochlear functions of patients with acoustic neuromas]

Electrocochleographic cochlear microphonics (ECochG-CM) and Evoked Otoacoustic Emissions (EOAE) were recorded for 17 patients with acoustic neuromas to assess their cochlear functions. ECochG-CM was recorded by a transtympanic needle electrode technique. The acoustic stimuli of EOAE were short tone bursts and thresholds of detection of the slow components were determined. In 13 of the 17 patients, elevated detection thresholds of ECochG-CM and/or abnormal interaural differences in detection thresholds of the slow components of EOAE were observed. The patients with hearing loss and an elevated thresholds of CM were believed to have cochlear impairments. Those with hearing loss and a relatively low detection threshold of CM were thought to have cochlear nerve damage and a smaller degree of cochlear impairment. The correlation of ECochG-CM and EAOE was 0.799. Both ECochG-CM and EOAE were useful in evaluating the cochlear functions of patients with acoustic neuromas. Although EOAE was easier to apply clinically, ECochG was indispensable when detailed examinations of cochlear functions were necessary.