Radiology Resident Case of the Week
Etiology/Pathophysiology:
Organisms must be introduced into the brain from an outside source such as in a bacteremia, abcess, SBE, or instrumentation of the heart. Experimental studies show that once the organism seeds into the vessel, there is inflammation and necrosis of the vessel wall leading to aneurysmal dilation.
Pathology:
Approxiamately 3% of all patients with endocarditis develope small aneurysms on the distal branches of the middle, anterior or posterior cerebral arteries. About 65% of these rupture within the first five weeks with a high mortality rate. The most common organisms involved are S. aureus and Strep viridans.
Miscellaneous:
Imaging:
Brain CT- shows blood within the silvian fissure.
Angio-shows small aneurysm in a distal branch of the left MCA.
DDx:
1) Mycotic aneurysm
2) vasculitis
Key references:
Greedfield Neuropathology, 5th edition, p 293.
Osborn
ACR Code:
Keywords: aneurysm, infection, vasculitis