Electrocochleographic changes in acoustic neuroma: some experimental findings.

Reversible experimental lesions were produced in the central end of the cochlear nerve at the IAM of guinea pigs by various procedures, including the instillation of KCl (0.1 or 0.01 M). As a result the usual diphasic AP waveforms seen in guinea pigs (when click stimuli are used) were transformed into monophasic, widened negative waves. This change, attributed to a neural block, was reversible, e.g. when the instilled KCl was dispersed by irrigation with normal saline. It is suggested that the widened monophasic negative AP's observed at ECochG in cases of acoustic neuroma or similar lesions, are produced in this way.