Reorganization of the cortico-spinal pathway in patients with chronic complete thoracic spinal cord injury: a study of motor evoked potentials.

OBJECTIVE To evaluate the change in motor evoked potential parameters following transcranial magnetic stimulation in patients with chronic complete thoracic cord injury. DESIGN A cross-sectional study. SUBJECTS Eighteen patients with chronic complete thoracic cord injury and 18 age- and sex-matched healthy controls were included in the study. The mean post-injury duration was 13.0 (standard deviation (SD) 6.0) years. METHODS The latency, amplitude, central conduction time and peripheral conduction time of motor evoked potentials from bilateral abductor pollicis brevis and first dorsal interosseous muscles following transcranial magnetic stimulation were measured and compared between the patients and healthy controls. The predicting variables for central conduction time, including age, sex, height, illness duration and job activity, were analysed using a simple correlation and stepwise multiple regression model. RESULTS The patients with complete thoracic cord injury had longer central conduction time recording of the dominant hand in both abductor pollicis brevis and first dorsal interosseous muscles. The difference in latency approached significance between the patients and controls. There was no statistical difference in amplitude between them. Regression analysis demonstrated that patients who were older, less physically active and with longer illness duration showed prolonged central conduction time. CONCLUSION The central conduction time in the dominant hand of chronic complete thoracic cord injury is prolonged. This study revealed motor reorganization of the central nervous system in complete thoracic cord injury. Decreased physical activity and prolonged illness may cause these changes.