Adaptation in the motor cortex following cervical spinal cord injury

Background. The nature of the adaptive changes that occur in the cerebral cortex following injury to the cervical spinal cord are largely unknown. Objective: To investigate these adaptive changes by examining the relationship between the motor cortical representation of the paretic right upper extremity compared with that of the tongue. The tongue was selected because the spinal cord injury (SCI) does not affect its movement and the cortical representation of the tongue is adjacent to that, of the paretic upper extremity. Methods: FMRI was used to map cortical representations associated with simple motor tasks of the right upper extremity and tongue in 14 control subjects and 9 patients with remote (>5.5 months) cervical SCI. Results: The mean value for the site of maximum cortical activation during upper limb movement was identical between the two groups. The site of maximum left hemispheric cortical activation during tongue movement was 12.8 mm (p<0.01) medial and superior to that of control subjects, indicating the presence of a shift in cortical activation. Conclusion: The findings indicate that the adult motor cortex does indeed adapt following cervical SCI. The nature of the adaptation and the underlying biological mechanisms responsible for this change require further investigation.