Neural plasticity after spinal cord injury

Abstract

Spinal cord injury (SCI) has devastating physical and socioeconomical impact. However, some degree of functional recovery is frequently observed in patients after SCI. There is considerable evidence that functional plasticity occurs in cerebral cortical maps of the body, which may account for functional recovery after injury. Additionally, these plasticity changes also occur at multiple levels including the brainstem, spinal cord, and peripheral nervous system. Although the interaction of plasticity changes at each level has been less well studied, it is likely that changes in subcortical levels contribute to cortical reorganization. Since the permeability of the blood-brain barrier (BBB) is changed, SCI-induced factors, such as cytokines and growth factors, can be involved in the plasticity events, thus affecting the final functional recovery after SCI. The mechanism of plasticity probably differs depending on the time frame. The reorganization that is rapidly induced by acute injury is likely based on unmasking of latent synapses resulting from modulation of neurotransmitters, while the long-term changes after chronic injury involve changes of synaptic efficacy modulated by long-term potentiation and axonal regeneration and sprouting. The functional significance of neural plasticity after SCI remains unclear. It indicates that in some situations plasticity changes can result in functional improvement, while in other situations they may have harmful consequences. Thus, further understanding of the mechanisms of plasticity could lead to better ways of promoting useful reorganization and preventing undesirable consequences.

Fig. (1)

Etiology of SCI since 1990.

Fig. (2)

Organization of the motor cortex. a. Normal macaque monkey. B. Macaque monkey with long-standing amputation of a forelimb. These partial motor output maps include the representation of the face to the upper trunk. X indicates that no response could be elicited. (D, dorsal; M, medial; R, rostral.) (Adapted with permission from Raineteau et al., Ref. . © 2001 Nature Publishing Group).

Fig. (3)

Evidences of changes at each level of the somatosensory core after chronic SCI. A symbol indicates there is evidence for that particular type of change at the level. No symbol indicates lack of evidence for that type of change at that level. (Information extracted from Wall et al., Ref. , Fig. 3c. © 2002 Elsevier Science B.V.).