The effects on auditory function of damage to the pontine olivo-cochlear bundle in man.

A patient with multiple sclerosis (MS) in whom a lesion developed in the pons between successive nuclear magnetic resonance image scans (MRI) is described. The patient developed intolerance of loud sounds, with distorted perception of speech and music, and abnormalities of stapedius reflex threshold, masked speech audiometry, and masking level difference assessment in the presence of an unchanged pure tone threshold. These abnormalities partially resolved over a number of months. It is postulated that the efferent olivo-cochlear bundle was involved on one side of the pons and the abnormalities are interpreted in terms of bilateral removal of inhibition from the hair cells of the cochlea.