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Pathogenesis of widened AP-SP complexes often noted in electrocochleograms (ECochGs) in cases of cerebellopontine angle tumors remains unclear. As acoustic neuromas usually originate from the vestibular nerve, some changes in this nerve might be involved in producing the broadened waveform. Effects of lidocaine on the AP-SP complex were investigated in guinea pigs by injecting this compound into the root exit zone of the vestibular nerve, where the cochlear efferent fibers run together. The AP-SP complex in response to clicks and tone bursts was recorded at the bony wall of the scala vestibuli in the basal turn of the cochlea. Inactivation of the efferent cochlear fibers resulted in a marked widening of the waveform, independent of the interstimulus intervals (ISIs). This broad wave was composed of a DC shift which was quite similar to the envelope curve of the acoustic stimuli. Although the effect of activity of the efferent cochlear fibers on negative summating potential (SP) has not been reported in detail, the authors concluded that the broad waveform observed in ECochGs in cases with cerebellopontine angle tumors was caused by enhanced negative SP due to inactivation of efferent cochlear fibers.

The present experiment examined the effect of anoxia on the spontaneous discharges of cochlear single units in guinea pigs; several additional animals were tested for the combined effect of anoxia and sodium salicylate. Following the induction of anoxia, initial increases in the number of spontaneous discharges were seen in 19 of the 34 cochlear single units tested. Neurons showing high frequencies during normal respiration tended toward increased rates of discharge during anoxia. In the 5 animals pretreated with sodium salicylate, remarkable increases in the spike rates were noted following the induction of anoxia.

In order to investigate the clinical factors relating to positive glycerol tests, 51 patients with Ménière's disease were subjected to a complete battery of audiometric examinations, including the short increment sensitivity index, Bekesy, alternate binaural loudness balance, speech discrimination and pure-tone audiometry tests, both before and after glycerol ingestion. The correlation between positive glycerol tests and vestibular response, cochlear symptoms, age at onset and disease duration was investigated. High ratios of positive tests were obtained in the following categories of patients with Ménière's disease: elderly patients with vertiginous attacks; patients with high-level hearing loss; nystagmus patients, and patients with fluctuating hearing loss.

Five specimens of the endolymphatic sac taken from patients with Ménière's disease during epidural drainage surgery were examined under the electron microscope. The clinical history and histopathological findings are presented. The most common and prominent finding was perisaccular fibrosis of the endolymphatic sac which appears to disturb the free absorption of endolymph in the endolymph in the endolymphatic sac resulting in endolymphatic hydrops. Well-preserved epithelial cells of the endolymphatic sac could only be found in one of the specimens.