Abstract
Auditory evoked responses (ABR, MLR, SVR, ECochG) were recorded in five patients with pontine glioma. The aims were to examine possible mechanisms by which the disease causes response abnormalities and to evaluate the diagnostic potential of auditory evoked responses for detecting pontine glioma.
1. Abnormalities of the ABR were recorded in all cases.
2. Only wave I of the ABR was observed in three of the five sides in which the infiltrating tumor edge was in contact with the cerebellopontine angle cistern.
3. Results of ECochG in three cases provided evidence that functions of the cochlea were not impaired. In two of 3 cases, the AP thresholds were better than subjective thresholds at 4kHz.
4. Even in the sides with only wave I of the ABR, MLRs and/or SVRs were recorded in some cases.
The ABR examination is of excellent clinical value in detecting functional abnormalities resulting from infiltration by pontine glioma. The dominant effect of pontine glioma causing hearing disturbance is on the brainstem, probably as a result of direct invasion. Physiologically, it can be surmised that impaired synchronization of firing is an important mechanism causing abnormalities of auditory evoked responses.
