Specific Imaging Findings

Ependymal cysts (EC) are rounded or oval cysts with thin walls that are located within the lateral ventricles or subependymally, the most common site being the atrium. On CT they appear hypodense to the brain and of same attenuation as the CSF. Calcifications are usually not present. On MRI, the signal intensity of EC is similar to the CSF on all pulse sequences. Sometimes a slightly hyperintense signal relative to CSF on T1 and FLAIR sequences may be found due to increased protein content. The cyst wall is usually not visible on CT, but it is detectable on MR images, especially with 3D high-resolution heavily T2-weighted sequences (such as CISS, FIESTA, and DRIVE). The cysts do not enhance with contrast and show the same signal as the CSF on diffusion imaging. Post-contrast images may be useful as they demonstrate tiny venous vessels that are located around the margins of the cyst and this information can help in the surgical approach planning.

Pertinent Clinical Information

EC is usually asymptomatic, discovered incidentally, and typically stable on follow-up examinations. In rare instances they may cause entrapment of the ventricle or obstructive hydrocephalus and then may manifest with headache and seizures. The management is typically conservative, it depends on the size of the cyst and the presence of symptoms. Surgical treatment is required only in very large cysts or in symptomatic patients.