Destruction of the “Pyramidal Tract” in Man

Abstract

PPORTUNITIES to observe the results of the isolated destruction of the "pyramidal tract" in man are rare. There are but few places in the nervous system where the corticospinal fibers are separated sufficiently from other systems to permit of their isolated destruction, either surgically or by disease. Extirpation of the pre-and postcentral cerebral cortex results in a destruction of the "pyramidal tract" but also destroys other fibers, both ascending and descending, thus producing a complex picture. Lesions of the internal capsule frequently destroy the corticospinal system but they also destroy descending pathways to the basal ganglia, the thalamus, the brain stem, the cerebellum, etc., as well as many ascending fibers. Lesions in the spinal cord, likewise, cannot be confined to the corticospinal fibers. Only in the pyramids of the medulla oblongata can truly isolated lesions of the "pyramidal tract" be made. Although division of the medullary pyramids has been made in animals (cat and monkey),~6,27 it has not been carried out in man and at the moment no occasion to do so seems likely to arise. In the cerebral peduncle the corticospinal fibers are found segregated from all ascending fibers 24 and from all descending pathways except those passing from the cerebral cortex to the brain stern and cerebellum. The corticospinal fibers from the precentral cortex (the classi

Anatomic Location and Somatotopic Arrangement of the Corticospinal Tract at the Cerebral Peduncle in the Human Brain

“…Before development of DTI, a number of studies attempted to elucidate the location and somatotopic arrangement of the CST at the CP of the human brain by using the wallerian degeneration phenomenon on brain CT or MR imaging following brain injury, 7-12,29,30 direct brain stimulation study during surgery, 15,31 or pedunculotomy for control of involuntary movements. 5,6 Although there seems to be a general consensus that the CST occupies the middle portion of the CP and that the somatotopies for the arm and leg are arranged mediolaterally, some controversies still exist. Moreover, studies elucidating detailed anatomic information have been limited.…”

“…[1][2][3][4] Due to its anatomic characteristics, occurrence of a brain injury at the CP could result in severe neurologic deficits. 5,6 Therefore, detailed clarification of the anatomy of the CP would be important for clinical neuroscience. The CST is the most important motor pathway in the human brain.…”

A Revised Clinical Assessment of Motor and Memory Disturbances

“…The descending fibers contained in the pyramid consist not only of the corticobulbar and corticospinal tract fibers of Betz cell origin in the primary motor cortex but also of descending fibers originating from various cortices outside the primary motor cortex. The pyramidal tract is certainly related to voluntary movements, but, as reported by Bucy,4) voluntary movements will recover to a considerable extent even after complete transaction of the pyramidal tract.…”

Stretch Hyperreflexia of Triceps Surae Muscles in the Conscious Cat after Dorsolateral Spinal Lesions

“…Interruption of the corticospinal tract could contribute to hyperreflexia after interruption of the DLF (Wagley, 1945;Bucy et al, 1964;Woolsey, 1971). However, the lesions in the present study did not extend throughout the location of the corticospinal pathway.…”

“…However, the lesions in the present study did not extend throughout the location of the corticospinal pathway. Also, the Babinski sign and reflex that are presumed to result from corticospinal damage (Bucy et al, 1964) were only observed occasionally. Release of the Babinski reflex has been regarded as an example of an exaggerated flexion reflex (Walshe, 1956) that is not always associated with increased flexor reflex activity (Van Gijn, 1978).…”