Animal model acoustic neuroma.

As part of an effort to develop a longterm animal model simulating the effects of acoustic neuromas, a series of shortterm electrophysiological experiments were performed in the cat. The eighth nerve, as it exits the internal auditory meatus, was exposed and a silicone baloon catheter secured over the nerve. Pure tones and clicks were introduced ipsilaterally and primary evoked potentials were recorded from the contralateral auditory cortex. Alterations in the evoked potentials were examined as the baloons were inflated and deflated. Several reproducible phenomena were recorded: (1) contact between the silicone balloons and eight nerves resulted in substantial reductions in the evoked potential; (2) there was a further reduction in the evoked potential with inflation of the indwelling balloons; and (3) there was a prolongation of the latency period between auditory stimulation and the onset of the evoked potential with balloon inflation. All of these phenomena were reversed when either the contact was broken or balloons deflated.