Cerebral hemispherectomy was performed in a series of ten cats. Five hemispherectomies were on the right side and five on the left. These animals were clinically observed for periods varying from a few days to three weeks. Three of the ten cats were sacrificed on the 21st postoperative day and the brain stem and spinal cord were stained with the Swank-Davenport staining method to observe the secondary degeneration in the brain stem and spinal cord.
In this study one cerebral hemisphere was removed preserving the thalamus and caudate nucleus. However, autopsy showed partial damage of the thalamus in one of the three cats.
The postoperative physiological findings were as follows: All experimental cats showed slight hemiparesis on the contralateral side when they awoke from the anesthesia but usually they could get up and walk within a day and showed almost equal motor function in all extremities. However, careful examination revealed a very slight hemiparesis of the contralateral extremities. Usually the hindlimb was more severely affected than the forelimb. This hemiparesis of the contralateral side gradually improved and within a few days they showed almost equal strength in all extremities.
The persistent neurological findings included a contralateral homonymous hemianopsia and slightly decreased sensation on the contralateral side. When they walked, they turned to the operated side. This was ´ considered due to the contralateral homonymous hemianopsia.
Three of the ten cats developed generalized clonic convulsions on the third or fourth postoperative day and two of them expired shortly after the seizure.
The anatomical findings were as follows: In order to minimize postmortem artifacts the brain stem
and spinal cord were removed under deep nembutal anesthesia and the brain stem and spinal cord were stained with the Swank-Davenport staining method.
All experimental animals showed diffuse degeneration in the ipsilateral internal capsule but no degeneration was observed in the contralateral internal capsule.
All animals showed almost complete degeneration in the ipsilateral crus, pyramidal bundles, pyramid, decussating fibers and in the contralateral lateral pyramidal tract but no evidence of degeneration was observed in the contralateral crus, pyramidal bundles, pyramid or the decussating fibers.
Degenerated fibers in the contralateral lateral pyramidal tract were traced down to the lumbar or sacral level. However, there was no evidence of degeneration in the ipsilateral lateral pyramidal tract or the anterior pyramidal tract in any of the cats.
In the midbrain sections there were a few scattered degenerated fibers in the antero-lateral margin of the central gray matter( antero-lateral columnar fibers of Boyce,1895) on both sides in two cats, and on the ipsilateral side in one cat. In the position of the fasciculus longitudinalis rnedialis or antero-lateral columnar fibers of Boyce (1895), there were a very few scattered degenerated fibers on both sides in one of the three cats. In the position of the dorsal spinocerebellar tract where the accessory pyramidal bundle of Probst (1899) is located, there were a few degenerated fibers on both sides in one of the three cats. These degenerated fibers were found from the section at the level of the obex to the T1O level.
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