Giant basilar aneurysm in the course of subacute bacterial endocarditis.

We describe a man aged 42 years with mitral valve regurgitation who suffered from subacute bacterial endocarditis caused by Streptococcus morbillorum. The clinical picture began with a toxic syndrome. Five months later, the patient had an embolic episode and a right rostral pontine stroke, which was followed a few days later by an adversive focal seizure on the right. Despite antibiotic treatment, he suffered complete third nerve palsy. Arteriography, magnetic resonance imaging, and computed tomography of the brain showed a giant aneurysm in the rostral end of the basilar artery; the aneurysm was clipped. We discuss the clinical features, radiology, and characteristics of this aneurysm as a unique case of a giant bacterial aneurysm in the vertebrobasilar system.