Comparison of Central Motor Conduction Time Using Transcranial Magnetic Stimulation and Evoked Spinal Cord Potentials Following Transcranial Electrical Stimulation in Compressive Cervical Myelopathy

This study was performed to evaluate the accuracy of level diagnosis of cervical myelopathy using the measurement of the central motor conduction time (CMCT). In twenty-two patients with cervical myelopathy, the CMCT for the biceps brachii (Biceps) and the abductor digiti minimi (ADM) muscles were measured by subtracting the peripheral conduction time from the onset latency of the motor evoked potentials following transcranial magnetic stimulation. The peripheral conduction time was calculated by using T-waves for the Biceps and compound muscle action potentials following transcranial magnetic stimulation. The peripheral conduction time was calculated by using T-waves for the Biceps and compound muscle action potentials and F-waves for the ADM. Results　of the CMCT were compared with the evoked spinal cord potentials following transcranial electrical stimulation (TCE-ESCPs), which were recorded from the cervocal posterior epidural space at each intervartebral level during surgery. In all patients, abnormaliities of both the TCE-ESCPs and the CMCT for the ADM were shown. Moreover, the CMCT for the Biceps was also prolonged in all six patients with abnormalities of the TCE-ESCPs at C3-4, although it was prolonged in just three patients in sixteen patients with abnormalities at C4-5 or C5-6. The CMCT for the Biceps had the significant correlation with the dysfunction of the spinal cord at C3-4. This is useful for clinical diagnosis of the disordered level of cervical myelopathy.

moter evoked potential

central moter conduction time

transcranial magnetic stimuklation

spinal cord potential

cervical myelopathy