A 33 year-old man presented with a sudden, severe headache, nausea and vomiting. The next day, he abruptly deteriorated.

Axial CT scan - note the subarachoid hemorrhage in the basal cisterns and fourth ventricle. However, also note the prominent hydrocephalus with dilatation of the anterior and temporal horns, as well as the third and fourth ventricles. Acute hydrocephalus is a potential complication of subarachnoid blood, either impairing absorption of CSF or flow of CSF within the ventricular system. In this case, flow is most likely blocked at the arachnoid granulations resulting in communicating hydrocephalus. This picture requires emergency neurosurgery and ventricular shunting.

Revised 05/06/06.
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