[Electrocochleography possibilities in the differential diagnosis of hydrops and neural hearing loss].

Enhancement of the click-evoked summating potential causing a pathological summation to compound action potential ratio (SP/CAP) in patients with endolymphatic hydrops has been described by several groups. An increased SP/CAP ratio is found also in some patients with a tumour of the cerebellopontine angle. The study of further parameters of the SP/CAP complex, such as the CAP latency and the width of the complex, permit an electrocochleographic differentiation between both forms of hearing loss. The N2 amplitude showed no diagnostic significance.