Destruction of the "Pyramidal Tract" in Man* PAUL C. BucY, M.D., JAMES E. KEPLINGER, M.D., AND EDIR B. SIQUEIRA,M.D. Department of Surgery, Northwestern University Medical School and Section on Neurological Surgery, Chicago Wesley Memorial Hospital, Chicago, Illinois PPORTUNITIES to observe the results cal "pyramidal tract") occupy the central of the isolated destruction of the portion of the cerebral peduncle (Fig. 1) as O "pyramidal tract" in man are rare. Levin ls,19 has shown, while the corticospinal There are but few places in the nervous sys- fibers from the postcentral region lie immedi- tem where the corticospinal fibers are sepa- ately lateral to these (Fig. ~).1 In the most rated sufficiently from other systems to per- medial part of the peduncle are found the mit of their isolated destruction, either surgi- frontopontine fibers, ls,19 The exact nature of cally or by disease. Extirpation of the the fibers in the most lateral part of the cere- pre- and postcentral cerebral cortex results in bral peduncle is less well known. Marin a destruction of the "pyramidal tract" but et al., 2~ from a study of human material con- also destroys other fibers, both ascending and cluded that the lateral segment of the pe- descending, thus producing a complex pic- duncle is composed of corticopontine fibers ture. Lesions of the internal capsule fre- from the parietal, occipital and temporal quently destroy the corticospinal system but lobes. However, their evidence as to occipito- they also destroy descending pathways to the pontine fibers is not conclusive, and that basal ganglia, the thalamus, the brain stem, dealing with a temporopontine component the cerebellum, etc., as well as many ascend- indicates only a very few such fibers. In fact, ing fibers. Lesions in the spinal cord, likewise, in their s cases of isolated lesions of the tem- cannot be confined to the corticospinal fibers. poral lobe they stated that in 1 (Case 3) there Only in the pyramids of the medulla oblon- was "no clear-cut evidence of degenerating gata can truly isolated lesions of the "pyram- fibers in the basis pcdunculi," and in the idal tract" be made. Although division of other (Case 4) in which the anterior part of the medullary pyramids has been made in the temporal lobe was amputated surgically animals (cat and monkey),~6,27 it has not been a "band of less dense gliosis (i.e., less dense carried out in man and at the moment no than in the white matter at a higher level) with occasion to do so seems likely to arise. In the no associated pallor of myelin occupies the cerebral peduncle the corticospinal fibers are most lateral part of the lateral segment" (of found segregated from all ascending fibers24 the peduncle). On the other hand, in those and from all descending pathways except cases in which the parietal cortex was in- those passing from the cerebral cortex to the volved (in addition to the temporal and brain stern and cerebellum. The corticospinal occipital cortices) the degeneration in the fibers from the precentral cortex (the classi- lateral segment of the peduncle was intense. Their material provided no evidence on the Received for publication September 3, 1963. question of corticospinal fibers from the * This study was aided by Grants Nos. B-151~, B- ~745 and NB 5408 from the National Institute of parietal area. NeurologicalDiseases and Blindness of the U. S. Public In recent years several surgeons have di- Health Service. vided various parts of the human cerebral pe- Presented with motion pictures before a special meet- ing of the Dutch Neurological Society in Utrecht on duncles, usually for the relief of abnormal in- October 4, 196~, a joint meeting of the Czechoslovakian voluntary movemcnts. 3,4, 8-11,21-23 ,25,29,30-32,~4 Neurological Society and the Neurosurgical Section of To our knowledge no one has had the oppor- the Czechoslovakian Surgical Society in Prague on June 17, 1968 and at the Medical School of the Free tunity previously to study the clinical results University of Berlin on June ~4, 1968. of such a lesion in man and then to examine 385 386 Paul C. Bucy, James E. Keplinger and Edir B. Siqueira FIG. 1. Diagrammatic representation of the position in the cerebral peduncle of the monkey of the fibers descend- ing from the frontal region. The lesions giving rise to the degeneration are shown above. The ipsilateral cerebral peduncle is shown below with its medial part toward the right. The degenerated fibers in the peduncle are indicated by stippling. Those from the precentral region occupy the central portion of the peduncle; those from the most anterior portion of the frontal lobe lie most medially. (Modified after Levin) ~9 the location and extent of the surgical lesion Walker 3~ and Guiot and Pecker 9'1~ have and of the resulting degeneration in the demonstrated that destruction of part of the human nervous system. The present report cerebral peduncle could relieve permanently concerns such an instance. the abnormal involuntary movements of In 1961 Bucy and Keplinger6 presented the hemiballismus and of parkinsonism. Experi- preliminary report of the case of a man in ence had led one of us 3,4 to believe that the whom the central portion of the cerebral surgical lesion to be effective must include peduncle was divided in order to relieve a the central portion of the cerebral peduncle. severe hemiballismus. Clinically the opera- This belief rested partly on the fact that tion was completely successful. The abnor- Meyers21-2a showed that section of the medial mal movements were abolished and never sector of the peduncle did not relieve such returned. The left extremities which were movements, and that Bucy4 demonstrated completely disabled prior to the operation that section of the lateral sector was likewise were returned to usefulness with almost ineffective. Meyers~2,~3 had reached a similar normal volitional control. The operation was conclusion. designed to divide the corticospinal fibers Levinls,19 (Fig. 1) and Barnard and Wool- from the precentral region, or the classical seyI (Fig. ~) showed that this central portion "pyramidal tract." As this study will show, it of the cerebral peduncle contains the cortico- was highly successful in that regard also. spinal fibers arising from the precentral re- FIG. ~. Diagrammatic representation of the position in the cerebral peduncle of the monkey of the fibers descend- ing from the pre- and postcentral cortices. The drawings showing the lesions in the cortex are above. The first three sketches show lesions in the "face," "arm" and "leg" areas respectively of the precentral cortex. The drawing farthest to the right illustrates an extensive lesion in the postcentral area. Beneath each of the drawings of a cortical lesion is the corresponding drawing showing the position in the cerebral peduncle of the degeneration of fibers produced by the cortical lesion. The medial part of the cerebral peduncle is to the left and the lateral part to the right. (Modified after Barnard and Woolsey) 1 .