Clinical Factors for Predicting Neurophysiological Improvements Upon Extension and Flexion in Cervical Spondylotic Myelopathy Patients: A Retrospective Cohort Study

Abstract

BackgroundCervical extension and flexion are generally thought to be harmful to CSM patients. Contrary to previous notions, a proportion of CSM patients presented DSSEP improvement upon extension and/or flexion. This study aims to determine the prediction criteria for DSSEP improvement upon extension and flexion with clinical and neutral-position imaging.MethodsCSM patients between 2015 and 2019 were retrospectively evaluated. The recorded outcomes were DSSEP changes upon extension and flexion, disease duration, modified Japanese Orthopedic Association (mJOA) score, gait impairment presence, weakness of upper limb muscles, and positive Hoffmann sign designation. The collection of MRI data included the compression ratio, the number of stenotic levels, the Mühle stenosis grade and disc degeneration stage of the most severe segment, and the presence of ligamentum flavum hypertrophy and intramedullary T2WI hyperintensity. Cervical alignment types were evaluated on plain cervical lateral radiographs.ResultsForty-nine patients were finally enrolled. Nine (18.4%) and 11 (22.4%) patients showed DSSEP improvement upon extension and flexion, respectively. Logistic regression analysis showed that an involved segment number ≤ 2 (P=0.018) and a straight/sigmoid cervical alignment (P=0.033) were significant criteria for predicting DSSEP improvement upon extension (probability: 85.7%). Mühle grade 3 (P=0.022) and disease duration ≤ 6 months (P=0.04) were significant criteria for predicting improvement upon flexion (probability: 85.7%).ConclusionsCervical extension and flexion might not necessarily cause deterioration and can even improve some CSM patients' neurological function at DSSEP examination. The involved segment number and cervical alignment were related to extension DSSEP improvement, while the stenosis grade and disease durations were related to flexion improvement. Our work suggests potential significance of educating CSM patients on maintaining individualized neck positions based on their clinical and radiographic findings.BaTrial registrationThe trial was retrospectively registered on April 30th, 2020 and the registration number is "[2020]151".