An Experimental Study of Total Hemispherectomy in the Cat

Abstract

Cerebral hemispherectomy, since its first application by Dandy (1928), has been a radical procedure applied to patients with infiltrating gliomas of one cerebral hemisphere, intractable convulsive seizures due to unilateral cerebral atrophy, Sturge-Weber syndrome or diffuse cerebral paragonimiasis. In these operations the caudate nucleus, thalamus and subthalamic structures have usually been spared. Although many fundamental contributions have been made in the field of experimental neurology through study of animals in which large portions of cerebrum had been removed or destroyed, few experiments have been performed to define the limit of [cerebral resection compatible with maintenance of consciousness and survival. The purpose of this study is to present the physiological and anatomical observations on the effect of total cerebral hemispherectomy in the cat. In this study, twenty healthy cats of both sexes weighing five to nine lbs. were subjected to one stage removal of all cerebral cortex, basal ganglia, and thalamus from one side of the brain. In ten cats total hemispherectomy was performed on the right side and in the other ten on the left. These experimental animals were clinically observed for periods varying from five to thirty eight days. All twenty cats that had total hemispherectomy survived the initial operative procedure, but five of these cats subsequently died within a week due to intracranial hemorrhage or infection. Five of the surviving fifteen cats were sacrificed within the fourteenth postoperative day and the other ten were sacrificed during the period from three to five weeks postoperatively. The brain stem and spinal cord was stained with the Marchi staining method to observe secondary degenerative changes of nerve fibers. The postoperative physiological findings were as follows: In spite of the extensive removal of the unilateral cerebrum including the thalamus, .all of these animals demonstrated early and rapid return of consciousness, giving evidence of awareness of environment by noting objects in their remaining homonymous visual' field. After recovery from anesthesia, the totally hemispherectornized cats demonstrated marked flaccid paralysis. of contralateral extremities but good motor function on the ipsilateral side. The contralateral flaccid paralysis recovered slightly in the forelimb on the second postoperative day and hindlimb improvement began on the third postoperative day. Although the cats usually could get up and walk within a few days and showed aJrrost ncrmal motor function within a week, the distal musculature of the contralateral extremities showed the least recovery. Following unilateral total hemispherectomy including the thalamus, these experimental animals were unable to respond to painful stimuli on the contralateral side when they awoke from anesthesia. However, painful stimulation was perceived over the contralateral face and extremities in twenty four hours, and maximum return of sensory function was accomplished by the third postoperative day