Pressure-induced modifications of the acoustic nerve. Part I: The acoustic reflex.

It is commonly thought that as an acoustic neuroma grows it exerts pressure on the acoustic nerve resulting in alterations of the acoustic reflex and brain stem audiometry. This hypothesis has not been confirmed. In this study in an animal model, acute pressure was applied to the nerves of the internal auditory canal, and changes in the acoustic reflex were measured. Our results support the theory that pressure on the acoustic nerve causes an increase in the rate of adaptation and a decrease in the amplitude of the acoustic reflex. The contralateral reflex appears to be the most sensitive indicator of these effects. We feel that this animal model can be useful to investigate the effects of pressure on the acoustic nerve.