The relationship between central motor conduction time and spinal cord compression in patients with cervical spondylotic myelopathy.

STUDY DESIGN: Retrospective study. OBJECTIVES: Few studies have reported a relationship between central motor conduction time (CMCT), which evaluates corticospinal function, and degree of spinal cord compression in patients with myelopathy. Thus, there is no consensus on predicting the degree of prolonged CMCT on the basis of the degree of spinal cord compression. If a correlation exists between CMCT and spinal cord compression, then spinal cord compression may be a useful noninvasive clinical indicator of corticospinal function. Therefore, this study evaluated the relationship between CMCT and cervical spinal cord compression measured by magnetic resonance imaging (MRI) in patients with cervical spondylotic myelopathy (CSM). SETTING: Hiroshima University Hospital in Japan. METHODS: We studied 33 patients undergoing laminoplasty. Patients exhibited significant cervical spinal cord compression on both MRI and intraoperative electrophysiological examination. We assessed transcranial magnetic stimulation measurement of CMCT; spinal cord compression parameters such as area, lateral diameter, anteroposterior diameter and flattening of the spinal cord at the lesion site and C2/3 levels on MRI; and pre- versus postoperative Japanese Orthopaedic Association (JOA) scores. RESULTS: Correlations between CMCT and flattening as well as anteroposterior diameter of the spinal cord at the lesion level were observed. Strong correlations between CMCT and the ratio of the flattening and anteroposterior diameter parameters at the lesion level to that at the C2/3 level were also observed. CONCLUSIONS: Measurement of spinal cord compression may be useful for the evaluation of corticospinal function as a proxy for CMCT in patients with CSM.