The Contribution of the Precentral Gyrus to the Pyramidal Tract of Man

Abstract

T ItE origin of the pyramidal tract of man is not known. For carnivores, TM monkeys, 17 and man, I4 virtually all fibers arise from the neocortex, but the exact contribution of each cortical area is known only for the cat ~9 and macaqueY In man this noteworthy lack of information results from the improbability that ordinary brain lesions will be restricted to specific cortical areas. The lesions of natural disease, trauma, and, except in rare instances, congenital malformations 3 are much too diffuse to approximate the precision of experimental cortical ablations. Since the usual clinical material is of little help in locating the areas of origin of the pyramidal tract, any ease which approxilnates the experimental ideal gains in importance. In the case reported here, the cortical arm, trunk, and leg area of a patient was surgically removed under unique circumstances comparable to experimental conditions. The clinical features, some of which have been reported before, 4,5 are important in evaluating the resulting degeneration in the pyramidal tract. Case Report The patient's birth and early infancy were uneventful. At the age of 2-} years, she was found to have purposeless, involuntary movements of her left arm and left leg. These movements continued and, at the time of her first hospital admission at the age of 25, were described as an arrhythmic torsion spasm occurring at a rate of about one per second in the left arm including the shoulder, elbow, and wrist. There was little evidence of spasm in the left hip or knee, but the ankle showed internal rotation and plantar flexion. There was some weakness of the left hand; the left lower abdominal reflex was not obtained, but