Background and Purpose--The somatotopic organization of the corticospinal fibers is of importance because it is related to certain stroke syndromes. Although it has been suggested that motor fibers are somatotopically arranged in the corona radiata, the evidence is still insufficient in human.

Methods--The relative anteroposterior and mediolateral location of the lesions was measured on T2-weighted MRI in 28 patients who developed isolated motor deficit limited to the arm, leg, or bulbofacial muscles after a small corona radiata infarct.

Results--The location of the lesions associated with bulbofacial, arm, and leg paresis showed anterolateral-to-posteromedial distribution.

Conclusions--The results suggest that motor fibers subserving the bulbofacial, arm, and leg muscles are somatotopically arranged at the level of the corona radiata.