The motor conduction of cervical spondylotic myelopathy with intramedullary high signal intensity on MRI

We investigated an influence of the T2 weighted MR imaging (MRI)-documented intramedullary high signal intensity (IMHSI) on the motor conduction in cervical spondylotic myelopathy (CSM) patients. We measured the central motor conduction time (CMCT) and the latency from anterior horn cell to rootlet (CRL) of Biceps Brachii (biceps), Triceps Brachii (triceps) and Abductor Policis Brevi (APB) of 58 hands of 29 patients. The severity of myelopathy was evaluated by Japan Orthopaedic Association Scoring system (JOA score). CMCT of APB demonstrated good relationship (r=0.71, p=0.0001) with JOA score whereas no relationship existed in measurement of the CMCT of the biceps nor the triceps. And only the CMCT of the APB of the patients with IMHSI were significantly longer (Mann Whitney-U-test, p<0.05) than that of the patients without IMHSI. CRL had no relationship with the localized site of the high intensity area. The motor conduction time measurement could not diagnosis the localized site of IMHSI. The motor fiber of APB was more vulnerable than that of the biceps and the triceps in the spinal cord with IMHSI.