Etiologies such as mycotic or oncotic aneurysms should be considered in this location. Septic emboli from endocarditis may cause brain abscess, mycotic aneurysm, or vasculitis. Septicemia from any cause may lead to endocarditis, but the most common is S. aureus endocarditis in IV drug abusers. The aneurysms are commonly located superficially over the convexities. These lesions may respond to antibiotics, but may enlarge on follow up examination and require surgery.
Oncotic aneurysm is a similar process caused by embolization of atrial myxoma tissue.
Mycotic aneurysms have a higher risk of bleeding than congential aneurysms.