Cortical motor reorganization after paraplegia - An EEG study

Objective: To determine whether a previously identified posterior reorganization of the cortical motor network after spinal cord injury (SCI) is correlated with prognosis and outcome. Methods.-We applied the techniques of high-resolution EEG and,dipole source analysis to record and map the motor potentials (MPs) of the movement-related cortical potentials in 44 patients after SCI. Twenty normal controls were also tested. Results were analyzed using a distance metric to, compare MP locations. EEG was coregistered with individual specific MR images and a boundary element model created for dipole source analysis, Results: MPs with finger movements were mapped to a posterior location in 20 of 24 tetraplegics compared with normal controls. Two patients, one studied 4 and one 6 weeks after injury, initially had posterior MPs that, on serial testing, moved to an anterior position with recovery; Dipole source localization of the MP generators confirmed these results. Nine of 20 paraplegics had a posterior MP location with actual or attempted toe movements. All 5 patients who could move their toes had posterior MPs. The MP was posterior in 4 of the 15 paralyzed patients. This is a significant difference in proportions, The only patient with paraparesis whose testing was repeated had an MP that moved to an anterior position with recovery. Conclusions: Posterior reorganization has a significant relationship to prognosis in paraplegia and is reversed in some SCI patients who recover function. Posterior reorganization may result from a preferential survival of axons that originate in somatosensory cortex and contribute to the corticospinal tract. These preliminary results should be verified by a larger prospective study.