[Lacune in the white matter revealed by MRI in a case of pure motor monoparesis].

It has been reported that most of pure motor monoparesis were induced by the superficial mass lesions in the cerebral hemisphere. However, pure motor monoparesis due to lacune is rare. We reported a 81 year-old woman of pure motor monoparesis caused by the lacunar infarction in the parasagittal subcortical white matter. That lesion could not be detected by CT scan performed at onset, and 18 days later after the stroke, but was detected by MRI performed 5 days after the onset. The coronal section of MRI showed the stick-like shaped small infarction in the white matter, which runs along the corticospinal tract, just under the precentral gyrus. The coronal section of MRI is useful for the demonstration of the anatomical localization of lacune.