Specific Imaging Findings

Tectal gliomas (TGs) are located in the tectum of the midbrain, which includes superior and inferior colliculi as well as periaqueductal gray matter. TGs expand the tectum and typically show iso-to low density and signal intensity when compared to the gray matter on non-contrast head CT and T1-weighted MR images. They are usually of increased T2 signal and diffusion. Post-contrast enhancement may be present, but this is not a common finding. The expansion of the tectum can be associated with stenosis or obstruction of the aqueduct and consequent hydrocephalus. Cystic component, calcifications, exophytic growth and tumor extension in the adjacent structures, primarily thalamus, may also occur. Displacement of the aqueduct is a common feature. Tumor size has been reported as a prognostic factor and should be assessed.

Pertinent Clinical Information

TGs are indolent tumors that usually become symptomatic in childhood. The most common presentation is headache and papilledema, which is related to hydrocephalus and resolves after ventricular shunting or ventriculostomy, the most common and essential clinical intervention. Other possible symptoms are Parinaud syndrome, nystagmus, sixth nerve palsy and dysmetria. The large majority of the TGs are low-grade and indolent, while a few show more aggressive growth and an infiltrating pattern, and high-grade gliomas are rare.