[A case of a bacterial brain abscess presenting as symptoms of 'sudden stroke-like' onset].

We report a case of a bacterial brain abscess presenting symptoms of 'sudden stroke-like' onset, associated with infective endocarditis. A 59-year-old woman experienced a sudden stroke-like onset of left hemiplegia. Computed tomography (CT) and magnetic resonance imaging (MRI) were performed on the day of ictus. No lesion responsible for the symptom was seen on either CT or a T2 weighted image (T2WI), but a diffusion-weighted image (DWI) revealed focal increased signal intensity in the right frontal lobe. An initial diagnosis of acute embolic infarction associated with infective endocarditis was made. Although the patient's neurological state had been stable, motor paresis of her left extremities became worse starting one month after her admission. MRI with gadolinium-diethylenetriaminepenta-acid (Gd-DTPA) at 37 days after admission showed an irregular-shaped ring-enhancement lesion located at the same place as the initial infarction, and in the left frontal lobe. Surgical drainage of the lesion in the right frontal lobe was performed, and diagnosed as a bacterial abscess. The exact mechanism of a bacterial brain abscess presenting with 'sudden stroke-like' onset is unknown, but various hypotheses have been proposed. One is that paroxysmal septic emboli lead to abscess formation within or near the area of embolic infarction. Our case showed that the creation of a brain abscess followed embolic strokes, and that this hypothesis was demonstrated by MRI carried out on the day of ictus.