Tectal plate gliomas. Part I: Microsurgery of the tectal plate gliomas.

A series of 12 patients with tectal plate gliomas, is presented treated by direct surgery. Mean age was 19 years. All patients presented with signs of raised intracranial pressure and supratentorial hydrocephalus on CT scan. Diplopia was the most common local sign. CT scan and MR imaging showed 4 intrinsic, 6 exophytic, and 2 ventrally infiltrating tectal tumours. The histological diagnosis was low-grade astrocytoma in 7, high-grade astrocytoma in 2, oligodendroglioma in one, oligo-astrocytoma in one, and ependymoma in one case. The suboccipital supra- and transtentorial approach was used in every cases. Tumour resection was generous at the level of the superior colliculi, but on the contrary, resection was limited at the level of inferior colliculi due to the auditory risk. Tumour removal was total (macroscopically) in 9 cases and partial in 3 cases. There were 4 surgical complications and one death related to surgery. Parinaud's syndrome was the most-common postoperative sequelae. Auditory hallucinations and the acoustic neglect syndrome were seen once. In three cases additional radiotherapy and chemotherapy were given once with severe sequelae. The treatment of tectal plate gliomas is controversial. The role of different therapeutic options remains open. We consider the tectal plate as a relatively safer territory for surgery than the ventral part of the midbrain. The brain stem auditory evoked potentials (BAEPs) and middle latency potentials (MLPs) monitoring can help to determine the appropriate limit of surgery.