Cortical sensorimotor reorganization after spinal cord injury: an electroencephalographic study

The aim of this study was to determine if cortical motor representation and generators change after partial or complete paralysis after spinal cord injury (SCI). Previously reported evidence for a change in cortical motor function after SCI was derived from transcranial magnetic stimulation. These studies inferred a reorganization of the cortical motor system. We applied the new technique of high-resolution EEG to measure changes in cortical motor representation directly. We recorded and mapped the motor potential (MP) of the movement-related cortical potentials in 12 SCI patients and 11 control subjects. Results were analyzed using a distance metric to compare MP locations between patients and control subjects. EEG was coregistered with subject-specific MR images and a boundary element model created for dipole source analysis (DSA). When compared with normal control subjects, seven quadriparetics had posteriorly located MPs with finger movements. One paraparetic had a posterior MP with toe movements, but three who could not move the toes had normally located MPs on attempts to move. DSA confirmed the electrical field map distributions of the MPs. We are reporting a reorganization of cortical motor activity to a posterior location after SCI. These results suggest an important role of the somatosensory cortex (S1) in the recovery process after SCI.