Isolated hand weakness in cortical infarctions.

Isolated hand weakness due to stroke is infrequently observed, and often misdiagnosed as peripheral lesions. This study investigated the clinical and radiologic profiles in such patients. Five men and one woman were studied. All patients underwent cranial magnetic resonance imaging (MRI) to confirm the diagnosis. Four patients had uniform weakness and the other two had either differential radial or ulnar weakness, respectively. MRI showed acute infarctions involving the hand knob area of the primary motor cortex (M1) in five patients and the postcentral gyrus sparing the precentral gyrus in one patient. Two patients with uniform digit weakness had additional involvement of the inferior parietal lobule. These findings suggest that isolated or predominant hand weakness in patients with cerebral infarctions is not necessarily caused by lesions in the M1 knob area, and that the control center of hand movement is not limited to the knob area alone.