Specific Imaging Findings

Colloid cyst is a round to oval midline intraventricular mass with sharp borders, with origin in the superior and anterior portion of the third ventricle at the foramina of Monro. The fornix columns appear splayed and wrapped around the anterior aspect of larger colloid cysts. The cyst is typically homogeneously hyperdense on CT (in about two-thirds of cases), while it can be isodense and very rarely hypodense. Wall calcifications are extremely rare. The mass is commonly T1 hyperintense, while the T2 signal ranges from low to high, and it can be iso to hypointense to brain on DWI with increased diffusion on ADC maps. Concentric layers or fluid-fluid levels of different signal may be present. Typically there is no contrast enhancement, although occasionally the capsule may enhance. The size of the cyst varies from a few millimeters to several centimeters, and it can be accompanied by obstructive hydrocephalus of the lateral ventricles.

Pertinent Clinical Information

Colloid cysts may be an incidental finding. When symptomatic, they present with headache, classically intermittent and positional, while nausea, vomiting, signs of intracranial hypertension, gait disturbance, visual deficits, memory loss, and altered personality may also occur. Symptoms are believed to be attributable to intermittent ventricular obstruction and hydrocephalus. There are several reported cases of sudden death in patients with non-specific headache, supposedly due to acute hydrocephalus and consequent brain herniation.