Abstract
Using a percutaneous magnetic stimulator, motor evoked potentials (MEP) induced by magnetic stimulation of the cerebrum and the cervical vertebrae were recorded at the muscles to calculate the central motor conduction time after magnetic stimulation CMCT (Mg) from the motor area of the cerebral cortex to the cervical part of the spinal cord, based on latency differences in MEP. Central motor conduction time by F waves CMCT (F) was calculated by subtracting the peripheral latency from the latency of MEP produced by cranial magnetic stimulation. The subjects consisted of 20 healthy subjects, 22 patients with cervical nerve compression, 18 patients with nerve root (C6 or C7) compression, and 24 patients with peripheral nerve compression. The mean CMCT (Mg) was 6.73ms, and the mean CMCT (F) was 5.56ms at the abductor pollicis brevis (APB) in healthy subjects. At the abductor digiti minimi (ADM), the mean CMCT (Mg) was 7.10ms, and the mean CMCT (F) was 6.05ms. Both CMCT (Mg) and CMCT (F) were significantly longer in patients with spinal compression than in healthy subjects. In patients with nerve root compression, CMCT (Mg) at the APB of the impaired side was significantly longer than that at the healthy side and that in healthy subjects.
These results suggest that CMCT (Mg) represents the time required to conduct nerve impulses from the motor area of the cerebral cortex to the outlet of the intervertebral foramen of the nerve root, while CMCT (F) represents the time required to conduct nerve impulses from the motor area of the cerebral cortex to the spinal ventral horn cells.
