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Dev Neurobiol. 2017 Jul;77(7):810-829. doi: 10.1002/dneu.22455. Epub 2016 Oct 14.

The corticospinal tract: Evolution, development, and human disorders.

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Institut du Cerveau et de la Moelle épinière, Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, F-75013, Paris, France.
Institut de Biologie Paris Seine, Neuroscience Paris Seine, Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, F-75005, Paris, France.
Département des Maladies du Système Nerveux, AP-HP, Hôpital de la Salpêtrière, Paris, France.


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.


axon guidance; development; mirror movements; movement disorders; pyramidal tract

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