Predominant involvement of a particular group of fingers due to small, cortical infarction

Background: Small cortical strokes may cause predominant weakness restricted to a particular group of fingers. However, clinical, radiologic, and etiopathogenetical studies have rarely been done in these patients. Method: The author analyzed clinical and radiologic features of 12 patients with small cortical infarcts who had predominant weakness of particular fingers. Results: The patients were divided into two groups: Eight patients had predominant involvement of ulnar-sided fingers (PIUF), and four had predominant involvement of radial-sided fingers (PIRF). Sensory symptoms were also present in eight patients, and the severity correlated with that of motor impairment. Radiologic-clinical correlation showed that the lesions related to PIUF were located significantly more medially than those associated with PIRF in the presumed hand representation area of the motor cortex. In addition, the PIUF was closely associated with severe proximal vessel stenosis or occlusion, whereas the PIRF was often related to emboligenic stroke. Conclusions: The results agree with traditionally alleged topography for fingers in the human motor cortex: ulnar fingers-medial and radial fingers-lateral. However, whether this result indicates a point-to-point somatotopical representation or differential threshold of excitability in individual neurons remains unknown. Sensory topography seems to be closely associated with that of motor function in individual subjects. The motor cortex representing ulnar-sided fingers may be a borderzone area between large arteries.