A study of examinations and surgical determinants of degenerative cervical myelopathy: the relationship between mri...

Motor evoked potentials measured by transcranial magnetic stimulation (Tc-MEPs) have been used to evaluate functional impairment in degenerative cervical myelopathy (DCM). Central motor conduction time (CMCT), calculated from the difference between MEP latency and peripheral nerve conduction time, is often prolonged in patients with DCM, 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.

We analyzed 137 patients with suspected DCM 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. Contrast Ratio was calculated as: CR = (SI narrow - SI cord) / (SI narrow + SI cord). Age, sex, and Japanese Orthopaedic Association (JOA) score, and MRI parameters including the Contrast Ratio (CR) at initial presentation were evaluated for associations with surgery. All patients in the surgical group were treated with cervical laminoplasty.

Lower-limb CMCT was positively correlated with Contrast Ratio (correlation coefficient = 0.209, p = 0.01). Multivariate analysis demonstrated that male sex, presence of intramedullary signal changes, and lower JOA scores were significantly associated with a higher likelihood of surgical intervention. Relationships were observed among intramedullary signal abnormalities, delayed CMCT, lower JOA scores, and the likelihood of surgery.

This study demonstrates that prolonged lower limb CMCT was significantly correlated with a higher Contrast Ratio. Therefore, we suggest that Contrast Ratio measurement may aid in evaluating DCM 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 DCM.