Level Diagnosis of Cervical Meylopathy by Transcranial Magnetic Stimulation

Abstract

Transcranial Magnetic stimulation can elicit a muscle response (MEP) from the target muscle with a voluntary contraction. MEPs were recorded from nineteen patients with cervical myelopathy due to single level compressin of the spinal cord. Central motor conductino time (CMCT) was also measured by subtracting the peripheral conduction time from the onset latencies of the MEPs. These methods were performed in biceps brachii (BB) muscles and abductor digit minimi muscles (ADM). The CMCT of BB and ADM were delayed in the cases with cord compression at C1/2 level. The CMCT of ADM was markedly delayed compared to that of BB in the cases with cord compression at C3/4 level. The CMCT of only the ADM was delayed in the cases with cord compression at C4/5 and C5/6 levels.
These results showed that comparison of the CMCT between the BB and the ADM is useful in the clinical diagnosis of the level of cervical myelopathy.