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Ann Clin Neurophysiol > Volume 8(1); 2006 > Article
Ann Clin Neurophysiol. 2006; 8(1): 29-35.
Diagnostic Value of Magnetic Motor Evoked Potential Parameters in Intramedullary Myelopathy
Sang Hyeok Seo, Yong Bum Kim, Heui Soo Moon, Pil Wook Chung, Jae Young An, Jong Seok Bae, Minky Kim, Kyong Jin Shin, and Byoung Joon Kim
Copyright © 2006 The Korean Society of Clinical Neurophysiology
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Background: Transcranial magnetic stimulation (TMS) is a non-invasive diagnostic method particularly suited to investigation the long motor tracts. The clinical value of TMS in most spinal cord diseases has still to be made. Diagnostic value of magnetic motor evoked potential (MEP) parameters in intramedullary spinal cord lesions was investigated.

Methods: MEP elicited by TMS was recorded in 57 patients with clinically and radiologically defined intramedullary myelopathy. Twenty five patients with cervical myelopathy (CM) and 32 thoracic myelopathy (TM) were included. Recordings were performed during resting and minimal voluntary contraction at both abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. Stimulation threshold(ST), amplitude, and central motor conduction time (CCT) were measured at resting and facilitated conditions. CCT was calculated by two means; central motor latency (CML)-M using magnetic transcranial and root stimulation, and CML-F using electrical F-wave study. The results were compared between patient groups and 10 normal control group.

Results: Facilitated mean ST recorded at TA was elevated in both CM and TM compared with control group. Resting mean CML-M at TA was significantly prolonged in both CM and TM, and CML-M was absent or delayed in 37.1% of CM and 8% of TM at APB with facilitation. Facilitated mean MEP amplitude at ABP was lower in CM than in TM, while MEP/M ratios were not different significantly between groups.

Conclusions: Magnetic motor evoked potential has diagnostic value in intramedullary myelopathy and localizing value in differentiating between CM and TM by recording at APB and TA. It is a noninvasive way to investigate the functional status of motor tracts of spinal cord.
Key words: Motor evoked potential, Myelopathy, Magnetic stimulation
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