A previously healthy 27 year-old woman developed a sudden, severe headache followed by nausea and vomiting.  By the time she reached the hospital, she was poorly responsive.  Her neurologic examination was non-focal.

Axial CT Scans without contrast: Note the bright areas which signify blood in Fourth Ventricle (left scan), the Sylvian fissure (middle scan) and posterior horns of the lateral ventricles (right scan).  Also note the enlarged ventricles (dilatation of the temporal horns) and effacement of the sulci over the convexity which indicates increased intracranial pressure. Spontaneous subarachnoid hemorrhage is most often caused by a ruptured aneurysm.  They usually present with hemorrhage and signs of increased intracranial pressure.  Rarely, an aneurysm may enlarge and present with focal signs from a mass effect, as is the case of a third nerve palsy and an aneurysm arising from the posterior communicating artery.

Revised 05/20/06.
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