A 26-year-old woman has had a fever for 5 days. On physical examination, her temperature is 38.2deg C, pulse is 100/min, respirations are 19/min, and blood pressure is 90/60 mm Hg. A cardiac murmur is heard on auscultation. Her sensorium is clouded, but there are no focal neurologic deficits. Laboratory findings include hemoglobin, 13.1 g/dL; platelet count, 233,300/ mm3; and WBC count, 19,200/ mm3. Blood cultures are positive for gram-positive bacteria. Urinalysis shows hematuria. An echocardiogram shows 1.5-cm vegetation on the mitral valve. Which of the following conditions is this patient most likely to develop?