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Basilar Artery Aneurysm

Findings:
Axial noncontrast CT shows a small mass in the interpeduncular cistern region in the expected location of the distal basilar artery. MR, MRA, and arteriography show the aneurysm at the tip of the basilar artery. The final arteriographic image shows successful coil embolization of the aneurysm.

Discussion:
Basilar artery aneurysms comprise approximately 10% af all intracranial aneurysms. The pathologic lesion is reduction or absence of the internal elastic lamina and/or media, either congenital or acquired, which markedly reduces elastic tension and allows expansion of the vessel diameter. 80-90% of nontraumatic subarachnoid hemorrhage is due to aneurysm. The risk of bleeding is approximately 2.5% per year for lesions >6mm in diameter, but any size aneurysm can bleed. Complications of SAH include hydrocephalus, rebleeding, vasospasm (>7d) +/- infarct. 1/3 of patients with ruptured aneurysm die immediately, 1/3 have long term disability, and 1/3 are normal.

  -grading SAH clinical: Hunt and Hess
   -0- unruptured
   -1- asympt or min H/A
   -2- mod/severe H/A, nuchal rigidity, CN palsy
   -3- drowsiness, confusion, mild focal deficit
   -4- stupor, mod/severe hemiparesis, early decerebrate, vegetative
   -5- deep coma, moribund
   -+1 for vasospasm or systemic disease

  -CT grading of SAH- Fisher
   -0- unruptured
   -1- no blood detected
   -2- diffuse <1mm
   -3- localized clot and/or vertical layer >1mm
   -4- intracerebral or IV clot with diffuse or no SAH

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