Gliomas of the tectum and periaqueductal region of the mesencephalon.

Gliomas that arise in the tectal and periaqueductal region of the mesencephalon usually present with hydrocephalus secondary to occlusion of the aqueduct of Sylvius. A review of 486 brain tumors in children treated during a 5-year period revealed 6 children with gliomas of the tectal plate. The 6 children were shunted for hydrocephalus, presumed secondary to aqueductal stenosis, prior to establishing the diagnosis of tectal plate glioma. No abnormalities were noted on the initial, uncontrasted computed tomography (CT) scans. The tumors are isodense without contrast enhancement which makes the CT diagnosis difficult. Magnetic resonance imaging (MRI) is diagnostic and demonstrates the characteristic enlargement of the tectum with increased density on T2 images. T1 density and gadolinium enhancement are variable. Pathological confirmation was obtained by open biopsy in 2 patients, a stereotaxic biopsy was performed on 2 children; 2 children were not biopsied. The tumor histology obtained was that of pilocytic astrocytoma. Two patients were treated with radiation therapy at the time of diagnosis. One child was followed closely and subsequently irradiated after tumor progression. All patients in this series are alive and functioning adequately 2-10 years after the onset of symptoms.