Presentation
Headache and vomitting.
Patient Data
Moderate hydrocephalus with dilated 4th ventricle continuous with infra-cerebellar cyst. The cerebellar vermis is compressed yet it appears intact and not rotated. Note the hyperdynamic signal void flow through the aqueduct of Sylvius and 4th ventricle.
Case Discussion
The case shows moderate hydrocephalus with dilated 4th ventricle continuous with an infra-cerebellar cyst. The cerebellar vermis is flattened yet it appears intact and not rotated. Note the hyperdynamic signal void flow through the aqueduct of Sylvius and 4th ventricle.
Blake's pouch cyst is caused by lack of fenestration of the Blake pouch, resulting in absence of communication between the fourth ventricle and the subarachnoid space. This will lead to cyst formation below and posterior to the vermis, which communicates with an open fourth ventricle.
The cerebellum has a normal size and shape.
Black pouch cyst could be differentiated from communicating hydrocephalus by communication of the 4th ventricle with the infra-cerebellar cyst.