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Neurology Feb 1990
Review
Topics: Brain Neoplasms; Cerebral Cortex; Humans; Movement; Neurons; Neurons, Afferent; Pyramidal Tracts; Spinal Cord
PubMed: 2405296
DOI: 10.1212/wnl.40.2.332 -
Developmental Neurobiology Jul 2017The corticospinal tract (CST) plays a major role in cortical control of spinal cord activity. In particular, it is the principal motor pathway for voluntary movements.... (Review)
Review
The corticospinal tract (CST) plays a major role in cortical control of spinal cord activity. In particular, it is the principal motor pathway for voluntary movements. Here, we discuss: (i) the anatomic evolution and development of the CST across mammalian species, focusing on its role in motor functions; (ii) the molecular mechanisms regulating corticospinal tract formation and guidance during mouse development; and (iii) human disorders associated with abnormal CST development. A comparison of CST anatomy and development across mammalian species first highlights important similarities. In particular, most CST axons cross the anatomical midline at the junction between the brainstem and spinal cord, forming the pyramidal decussation. Reorganization of the pattern of CST projections to the spinal cord during evolution led to improved motor skills. Studies of the molecular mechanisms involved in CST formation and guidance in mice have identified several factors that act synergistically to ensure proper formation of the CST at each step of development. Human CST developmental disorders can result in a reduction of the CST, or in guidance defects associated with abnormal CST anatomy. These latter disorders result in altered midline crossing at the pyramidal decussation or in the spinal cord, but spare the rest of the CST. Careful appraisal of clinical manifestations associated with CST malformations highlights the critical role of the CST in the lateralization of motor control. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 810-829, 2017.
Topics: Animals; Axons; Central Nervous System Diseases; Humans; Motor Skills; Nerve Net; Pyramidal Tracts; Spinal Cord
PubMed: 27706924
DOI: 10.1002/dneu.22455 -
Deutsches Arzteblatt International Mar 2022
Topics: Humans; Magnetic Resonance Imaging; Pyramidal Tracts; Wallerian Degeneration
PubMed: 35535722
DOI: 10.3238/arztebl.m2022.0013 -
Neurology Jul 1957
Topics: Humans; Pyramidal Tracts
PubMed: 13451883
DOI: 10.1212/wnl.7.7.496 -
Journal of Neurology Dec 2004The corticospinal tract develops over a rather long period of time, during which malformations involving this main central motor pathway may occur. In rodents, the... (Review)
Review
The corticospinal tract develops over a rather long period of time, during which malformations involving this main central motor pathway may occur. In rodents, the spinal outgrowth of the corticospinal tract occurs entirely postnatally, but in primates largely prenatally. In mice, an increasing number of genes have been found to play a role during the development of the pyramidal tract. In experimentally studied mammals, initially a much larger part of the cerebral cortex sends axons to the spinal cord, and the site of termination of corticospinal fibers in the spinal grey matter is much more extensive than in adult animals. Selective elimination of the transient corticospinal projections yields the mature projections functionally appropriate for the pyramidal tract. Direct corticomotoneuronal projections arise as the latest components of the corticospinal system. The subsequent myelination of the pyramidal tract is a slow process, taking place over a considerable period of time. Available data suggest that in man the pyramidal tract develops in a similar way. Several variations in the funicular trajectory of the human pyramidal tract have been described in otherwise normally developed cases, the most obvious being those with uncrossed pyramidal tracts. A survey of the neuropathological and clinical literature, illustrated with autopsy cases, reveals that the pyramidal tract may be involved in a large number of developmental disorders. Most of these malformations form part of a broad spectrum, ranging from disorders of patterning, neurogenesis and neuronal migration of the cerebral cortex to hypoxic-ischemic injury of the white matter. In some cases, pyramidal tract malformations may be due to abnormal axon guidance mechanisms. The molecular nature of such disorders is only beginning to be revealed.
Topics: Animals; Congenital Abnormalities; Embryonic Development; Humans; Macaca mulatta; Pyramidal Tracts
PubMed: 15645341
DOI: 10.1007/s00415-004-0653-3 -
Ergebnisse Der Physiologie,... 1969
Review
Topics: Animals; Cats; Haplorhini; Hominidae; Humans; Motor Neurons; Movement; Muscle Spasticity; Pyramidal Tracts; Rats
PubMed: 4983201
DOI: 10.1007/BFb0111447 -
Revista de NeurologiaTo review some anatomofunctional aspects of the pyramidal tract which are relevant in clinical practice, especially the newer concepts. (Review)
Review
OBJECTIVE
To review some anatomofunctional aspects of the pyramidal tract which are relevant in clinical practice, especially the newer concepts.
DEVELOPMENT
a) Although the motor function is best known, the pyramidal tract also has sensory functions, modulating the transmission of impulses in the spinal cord. In fact, motor function is a recent acquisition on the evolutionary scale. b) Other descending pathways, such as the cortico reticulospinal path, participate in voluntary movements. However, the pyramidal pathway is necessary for fine movements of the hand. c) Most of the pyramidal fibres control movements of the contralateral side of the body, but there are a few fibres which do not cross to the other side and play a part in ipsilateral body movements. These fibres seem to contribute to motor recovery following a brain lesion. d) Classically it is recognized that the motor cortex and pyramidal fibres follow a somatotopical distribution. Nevertheless territories corresponding to different parts of the body are superimposed to a considerable extent and may be modified on very diverse occasions. e) Experimentally it has been proved that a circumscribed lesion of the pyramidal pathway does not cause hyper reflexia or spasticity. The hyper reflexia and spasticity habitually seen in patients with pyramidal syndrome is due to lesions of other descending pathways.
CONCLUSION
The pyramidal tract is anatomically and functionally related to other nerve structures and its activity is therefore integrated within the nervous system.
Topics: Animals; Brain Mapping; Efferent Pathways; Extremities; Functional Laterality; Humans; Motor Activity; Motor Cortex; Motor Neurons; Muscle Spasticity; Pyramidal Tracts; Reflex; Reflex, Abnormal; Syndrome; Volition
PubMed: 11562847
DOI: No ID Found -
Revue Neurologique 1984The cortical origin of the pyramidal tract is first considered. Contributions of retrograde degeneration studies as well as fiber counting method following different... (Comparative Study)
Comparative Study Review
The cortical origin of the pyramidal tract is first considered. Contributions of retrograde degeneration studies as well as fiber counting method following different cortical lesions are presented and discussed. The results of these classical neuro-anatomical methods are compared with those of the more recent retrograde transport tracing method. The number and the diameter spectrum of pyramidal tract fibers differ in various mammals. In more evolved species the number of pyramidal fibers increase and their diameter span becomes wider. The thickest fibers are found in man. Along their diencephalic, mesencephalic, pontine and medullary course, axonal collaterals of corticospinal axons may terminate onto cells of origin of other descending pathways, onto relay cells of ascending pathways, and onto neurons projecting to the cerebellum. At the spinal level, the rostrocaudal extent and the termination area of corticospinal fibers may differ in various mammals. In a first group of mammals, the corticospinal fibers extend only to cervical or mid-thoracic segments and terminate in the dorsal horn. In a second group of mammals, the corticospinal fibers extend throughout the spinal cord and terminate in the dorsal horn and the intermediate zone. In a third group of mammals, the corticospinal fibers extend throughout the spinal cord and terminate in the dorsal horn, the intermediate zone and the dorsolateral part of the lateral motoneuronal cell group. In a fourth group of mammals, the corticospinal fibers also extend throughout the spinal cord and terminate in the dorsal horn, the intermediate zone and the dorsolateral as well as the ventral parts of the lateral motoneuronal cell group. A comparison is made between these different types of spinal terminations and the motor capacities of these different species. The motor deficits observed after pyramidal lesions are summarized and a comparison is made between the corticospinal tract and the descending brain stem pathways. According to electrophysiological studies in conscious animals different pyramidal units can be activated during different types of movements and at different times during the preparation or execution of a movement. Recent neuro-anatomical data suggest that the pyramidal tract is composed of many structural subsystems. Recent physiological data suggest that the pyramidal tract can be involved in various aspects of the motor control.
Topics: Animals; Axons; Brain Mapping; Cats; Cerebellum; Dogs; Electrophysiology; Extrapyramidal Tracts; Humans; Mammals; Motor Cortex; Movement; Pyramidal Tracts; Rabbits; Rats; Species Specificity
PubMed: 6379818
DOI: No ID Found -
Lancet (London, England) Mar 1958
Topics: Humans; Pyramidal Tracts
PubMed: 13515304
DOI: No ID Found -
Frontiers of Neurology and Neuroscience 2013Stroke is a leading cause of long-term disability with early accelerated followed by gradual recovery during the first 6 months after the ictus. The most important... (Review)
Review
Stroke is a leading cause of long-term disability with early accelerated followed by gradual recovery during the first 6 months after the ictus. The most important mechanism concerning early recovery is thought to be brain plasticity provided by anatomical and functional reorganization of the central nervous system after injury. Recent advances in noninvasive, functional brain imaging techniques provided some insight indicating the contribution of ipsilateral uncrossed corticospinal tracts in motor recovery after stroke. Since motor tracts vary considerably among subjects, the ratio of contralateral corticospinal tract fibers and their interhemispheric control versus the amount and function of ipsilateral corticospinal tract fibers may affect the scale of motor recovery after stroke. Further studies are needed to clarify the mechanisms of motor recovery after stroke in humans.
Topics: Adaptation, Physiological; Animals; Brain; Efferent Pathways; Humans; Neuronal Plasticity; Paresis; Pyramidal Tracts; Recovery of Function; Stroke
PubMed: 23859962
DOI: 10.1159/000348821