Contrast-Enhanced MRI-Based Grading of Nuchal Ligament Failure in Dropped Head Syndrome Caused by Isolated Neck Extensor Myopathy.

OBJECTIVE: To establish a contrast-enhanced MRI-based grading system for imaging-defined nuchal ligament disruption in dropped head syndrome (DHS) caused by isolated neck extensor myopathy (INEM), and to evaluate its association with sagittal head alignment, cervical extension function, pain, and quality of life.

METHODS: A total of 130 patients with INEM-related DHS who underwent contrast-enhanced cervical MRI were retrospectively analyzed, along with 21 non-DHS controls. Nuchal ligament findings were classified into four grades (Grade 0-3) based on contrast enhancement patterns and ligament continuity. Clinical parameters included chin-brow vertical angle (CBVA), pain severity assessed using the Numerical Rating Scale (NRS), health-related quality of life assessed using EuroQol 5 Dimensions (EQ-5D), and the ability to actively achieve cervical extension in the prone all-fours position. Associations among MRI grades were evaluated using one-way analysis of variance and multivariable regression adjusted for age and sex.

RESULTS: All patients with INEM-related DHS demonstrated intraligamentous contrast enhancement, whereas non-DHS controls showed no such findings. CBVA differed significantly across MRI grades, with higher values observed in patients with advanced-grade disruption. However, when MRI grade was treated as an ordinal variable, a strictly linear association with CBVA was not observed. Active cervical extension was rare in patients with Grade ≥2 disruption. Pain severity did not differ among grades. In contrast, EQ-5D scores were significantly lower in higher grades and remained independently associated with MRI grade after adjustment for age and sex. Interobserver reliability was moderate (weighted κ=0.62).

CONCLUSIONS: Contrast-enhanced MRI-based grading of imaging-defined nuchal ligament disruption provides a structural marker associated with sagittal head alignment and cervical extension dysfunction in INEM-related DHS. This classification may serve as a clinically useful adjunctive tool for severity assessment and stratification in selected patients.

STUDY DESIGN: Retrospective observational cohort study.