Case of the Month

Clinical

54 year old man presenting with headaches

Imaging

Non contrast CT - Small hyperdense lesion present at the foramen of Munro
MRI brain - Small lesion present at the foramen of Munro that is hyperintense on T1 and isointense to brain on T2 imaging. It showed no enhancement (post contrast images not provided).

Diagnosis

Colloid cyst

Discussion

Colloid cysts are a benign mucin containing cyst that originate when ectopic endodermal tissue migrates into the velum interpositum during embryogenesis. Approximately 3 people per million people per year are diagnosed with a colloid cyst. Even small colloid cysts can produce sudden acute hydrocephalus which can produce brain herniation and even death. Classically on imaging there is a small mass at the foramen of Munro that is hyperdense on CT, hyperintense on T1, with no enhancement as in the case provided.

Neurosurgical referral is recommended for evaluation.