Blake pouch cyst

Case contributed by Bouhouche Abdeldjalil
Diagnosis almost certain


Referred for further assesment of hydrocephalus seen on CT.

Patient Data

Age: 10 months
Gender: Male

There is an infravermian cyst that communicates with the fourth ventricle exerting a mild mass effect on the inferior part of the vermis which is of normal size (no vermian hypoplasia or rotation).

The cyst obstructs the CSF outflow at the level of the foramen of magendie causing upstream hydrocephalus involving the fourth ventricle and supratentorial ventricles (tetraventricular hydrocephalus).

The tegmento-vermian angle is normal (roughly zero degree).

The posterior fossa is not expanded.

Annotated image

The image illustrates the MRI findings in the setting of Blake pouch cyst.

Case Discussion

MRI findings are consistent with Blake pouch cyst.

The differential diagnosis includes:

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