A Study of Examinations and Surgical Determinants of Compressive Cervical Myelopathy: The Relationship between MRI Quantifications and Motor Evoked Potentials

Introduction: Motor evoked potentials measured by transcranial magnetic stimulation (Tc-MEPs) have been used to evaluate functional impairment in compressive cervical myelopathy (CCM). Central motor conduction time (CMCT), calculated from the difference between MEP latency and peripheral nerve conduction time, is often prolonged in patients with CCM, providing a quantitative indicator of neurological dysfunction. Intramedullary signal changes on MRI at sites of spinal cord compression are also observed; however, few studies have quantitatively assessed these changes. This study, quantified intramedullary signal alterations using contrast ratio (CR) to examine their relationship with CMCT and their influence on surgical decision -making. Methods: We analyzed 137 patients with suspected CCM who underwent Tc-MEP assessment between 2018 and 2024. CMCT for the upper and lower extremities was calculated from Tc-MEP results. On T2-weighted sagittal MRI, the region of interest was placed at the level of greatest spinal stenosis, and the MRI signal intensity (SI narrow) at this site was measured. Signal intensity of the normal spinal cord, at the T1 level (SI cord) was also recorded. CR was calculated as: CR = (SI narrow – SI cord) / (SI narrow + SI cord). Age, sex, and Japanese Orthopaedic Association (JOA) score at initial presentation were evaluated for associations with surgery. Results: Lower-limb CMCT was positively correlated with CR (correlation coefficient = 0.209, p = 0.01). Multivariate analysis demonstrated that sex, intramedullary signal changes at the stenotic level, and JOA score were significantly associated with surgical intervention. Relationships were observed among intramedullary signal abnormalities, delayed CMCT, lower JOA scores, and the likelihood of surgery. Discussion: This study demonstrates a positive correlation between lower-limb CMCT and CR, suggesting that CR measurement may aid in evaluating CCM severity. Moreover, surgical decisions were influenced by multiple factors, including intramedullary MRI changes, electrophysiological findings, and clinical presentation. Thus, comprehensive consideration of symptoms, imaging, and physiological assessments remains essential for treatment planning in patients with CCM.