Electrophysiological assessment of spinal cord lesions by means of transcranial cortical stimulation.

Central Motor Conduction Time (CMCT) was assessed in 30 healthy volunteers and 22 patients with spinal cord lesions due to compressive, degenerative and demyelinating disease. To obtain the CMCT, electrical Transcranial Stimulation and Percutaneous Spinal Stimulation or F wave calculations were employed. Pyramidal Tract (PT) conduction was always abnormal in the clinically impaired corticospinal tracts of all the studied patients. This results correlated with the degree of muscle weakness specially in those having compressive lesions. Subclinical evidence of pyramidal damage was also observed in two patients with Multiple Sclerosis. As opposed to the other groups, patients with degenerative spinal disease, showed essentially symmetric abnormalities. An important overlap of CMCT slowness was seen among the three studied groups, suggesting that this isolated clue is not valuable enough for aetiological suspicion. Double muscle responses due to single TCS were obtained, during rest, in some patients from each group, but never in controls. This pathological feature, not reported by others, could represent the excitation of indirect corticospinal connections, partially responsible for the residual motor function after PT damage.