Tectal plate gliomas. Part III: Apparent lack of auditory consequences of unilateral inferior collicular lesion due to localized glioma surgery.

The authors present one of their cases operated on for intrinsic tectal plate glioma. The complete resection of the right inferior colliculus (I.C.) had no apparent auditory consequences. The pre- and post-operative tonal and vocal auditory tests were normal. The brain-stem auditory evoked potentials (BAEPs) and middle latency potentials (MLPs) were recorded pre-, post- and intraoperatively. At the end of surgery all waves were present with a marked delay of wave V and a slight delay of the Pa component. The dichotic test showed a significant right ear extinction but admittedly much less important than expected. The role of inferior colliculus (I.C.) in hearing is discussed.