Silent intracerebral lesions identified on magnetic resonance imaging in patients presenting with initial stroke--comparative studies of the affected hemisphere and the contralateral one]

Among patients who had undergone MRI examinations with a clinical suspicion of stroke, we selected 82 patients with initial cerebral infarction being located only in a unilateral cerebral hemisphere. Seventeen (21%) subjects had wedge-shaped lesions including cerebral cortex (the cortical type), 65 (79%) had them predominantly in white matter and/or territory of the deep perforators (the subcortical type). Fifty nine cases out of total 82 (72%:9 in the cortical type, 50 in the subcortical type) had the silent cerebral infarction in the contralateral hemisphere to the affected side found on the 1.5 tesla superconductive system T2 weighted magnetic resonance imaging. Among them, 57 had the contralateral small cortical and/or subcortical (white matter) infarction, the other 2 cases had the contralateral lacunar infarction in the basal ganglia-internal capsule area as the silent lesion. The incidence of the cortical type was high in cases without the silent cerebral infarction in the contralateral hemisphere. It might be suspected that the cortical type had tendency to present clinical symptoms caused by initial stroke without prior silent cerebral infarction. The author proposed that the cerebral embolism might play an important role in showing the sudden onset clinical symptoms of the cortical type. And the author also proposed that there might be a difference in the development of clinical symptoms between the silent cerebral infarction located in the basal ganglia-internal capsule area and the cortical-subcortical (white matter) area.