Diagnosis:
Subarachnoid Hemorrhage from a Basilar Tip Aneurysm

History: 67 year old with severe headache after bumping right side of head on car

Discussion:
Findings confirmed on cerebral angiogram. The patient underwent coiling of the aneurysm.

Subarachnoid Hemorrhage can be a difficult diagnosis to make. Always survey the basilar cistern for iso/high density blood. View the comparison exam from 6 months prior and compare with the current exam. You will notice a higher density (hemorrhage) within the current study that was not present on the prior. Also, notice the aneurysmal dilatation basilar artery that is present on the prior exam. One of the important findings in this case is the mass effect on adjacent structures. This is seen by cerebral tonsillar herniation and narrowing of the ventricle outflow tract resulting in mild dilatation of the lateral ventricles.