Analysis of the Lesion Distributions and Mechanism of Acute Middle Cerebral Artery Infarctions Involving the Striatocapsular Region

BACKGROUND AND PURPOSE: There is no clear description about the patterns of each mechanism of striatocapsular infarctions. The aims of our study were to elucidate differences in the distributions of lesions of acute middle cerebral artery (MCA) infarctions involving the striatocapsular region and to compare those following embolic striatocapsular infarctions with those originating from MCA disease. METHODS: We prospectively enrolled patients with acute infarcts located in the lenticulostriate artery territory that were not lacunar infarcts. Brain coronal diffusion-weighted imaging (DWI) was obtained and magnetic resonance angiography (MRA) was carried out to evaluate the distribution of infarct lesions and MCA stenosis in all patients. The types of infarct distribution were divided into three categories: (1) dominant in the distal territory (DD), (2) distributed equally between the distal and proximal territories (DE), and (3) dominant in the proximal territory. We performed tests for embolic sources (transthoracic echocardiography, transesophageal echocardiography, Holter monitoring, and contrast-enhanced MRA including the aortic arch) in most patients. Stroke mechanisms were classified into stroke from proximal embolism, MCA disease, and stroke of undetermined etiology. RESULTS: A total of 47 patients (28 men and 19 women; mean age, 62 years) were recruited. A proximal embolic source was significantly more prevalent in patients with a DE lesion than in those with a DD lesion. The most common proximal embolic source was of cardiac origin. In contrast, symptomatic MCA stenoses were more common in patients with a DD lesion than in those with a DE lesion. CONCLUSIONS: These results suggest that the dominant area of striatocapsular infarction on coronal DWI is an important clue for stroke etiology. Coronal DWI could therefore be helpful to determining the mechanisms in patients with striatocapsular infarctions that are currently described as having an "undetermined etiology" according to the Trial of Org 10172 in Acute Stroke Treatment classification.