The function and morphology of the cochlea of the spontaneously hypertensive rat (SHR) were examined and compared with the age-paired normotensive Wistar Kyoto rat (WKY). Electro- cochleographic study revealed that the function of the cochlea in the SHR declined with increasing age to a greater extent than that of WKY. Electronmicroscopic study revealed that the primary site of the cochlear deterioration of the SHR was the vascular stria, followed by the organ of Corti. Some hypotheses to explain this phenomenon are proposed for further study.

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20 patients with sudden deafness were examined by electrocochleography (ECochG).The cochlear potentials such as AP, CM and SP were investigated both at the early stage of the disease and 2 to 4 weeks later. There was a significant difference in the cochlear potentials between the cases with remarkable hearing improvement and with improvement. In all cases whose SP/AP ratio was more than 0. 27, hearing improvement was obtained. The SP/AP ratio returned normal (about 0. 25), after the hearing recovery. It was concluded that the SP/AP ratio in ECochE might be very helpful in studying the prognosis of sudden deafness.

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