Clinical and Radiological Characterization of Cervical Spinal Stenosis Using Muhle Grading on Flexion-Extension Dynamic MRI: Correlation With mJOA in an Institutional Cohort.

Abstract

Study DesignObservational retrospective cross-sectional study.ObjectiveTo characterize patients with cervical spinal stenosis evaluated with flexion-extension dynamic MRI and assess the association between dynamic Muhle severity and modified Japanese Orthopaedic Association (mJOA) category.MethodsAdults undergoing sagittal T2 dynamic cervical MRI (neutral, extension, flexion) at a tertiary referral spine service (Mexico, 2024-2025) were included. Dynamic Muhle grade was the maximum across positions. We recorded spinal cord compression on neutral versus dynamic MRI, conversion to compression, increased compression, and an additional compressed level on dynamic sequences. T2 hyperintensity on neutral MRI was recorded as an additional imaging variable. Interobserver agreement was assessed across all readers, and intraobserver agreement in the principal readers. Exploratory diagnostic performance of neutral MRI relative to dynamic MRI was calculated. Ordinal logistic regression modeled mJOA category as the dependent outcome and dynamic Muhle grade as the principal predictor, adjusted for age and sex.ResultsFifty patients were analyzed (mean age 58.5±9.5 years; 62% female). Dynamic Muhle grades were 1: 10%, 2: 28%, and 3: 62%. Spinal cord compression was more frequent on dynamic than neutral MRI (90% vs 72%); conversion occurred in 18% and increased compression in 42%. Neutral MRI showed 80.0% sensitivity and 100% specificity relative to dynamic MRI for detecting compression. T2 hyperintensity on neutral MRI was present in 60% and correlated with higher dynamic Muhle grade (ρ=0.536, p<0.001). Interobserver agreement across all readers was moderate at the single-rater level and high at the averaged-rater level, whereas intraobserver agreement in the principal readers was excellent. In adjusted ordinal logistic regression, higher dynamic Muhle grade remained independently associated with worse mJOA category (OR 24.10; 95% CI 4.85-119.76; p<0.001).ConclusionsFlexion-extension dynamic MRI frequently reveals clinically relevant, posture-dependent cord compression underestimated on neutral imaging. Higher dynamic Muhle grades were strongly associated with worse clinical severity, supporting selective dynamic MRI when neutral findings are discordant with the clinical picture. Structured calibration in a teaching-hospital setting may improve reproducibility of Muhle grading.