The Cross-Sectional Areas and Anterior-Posterior Balance of the Cervical Paraspinal Muscles in Dropped Head Syndrome and Cervical Spondylotic Myelopathy: A Propensity Score-Matched Analysis

Introduction: Dropped head syndrome (DHS) is characterized by weakness of the neck extensor muscles. However, few studies have assessed the cross-sectional areas (CSAs) of the cervical paraspinal muscles (CPM) and their anterior-posterior balance in DHS. This study aimed to elucidate the pathognomonic findings of DHS by comparing the CSAs and anterior-posterior balance of the CPM in patients with DHS and cervical spondylotic myelopathy (CSM), using magnetic resonance imaging (MRI). Methods: We compared the CSAs and anterior-posterior balance of the CPM in patients with DHS and CSM using MRI. Patients with CSM were selected in an age- and sex-matched manner, using the propensity score. The longus colli (LC) muscle was selected as the anterior muscle; and the semispinalis cervicis (SSC), splenius capitis (SC), and multifidus muscles (MM) were selected as the posterior muscles. We calculated LC/SSC, LC/SC, LC/MM, and LC/(SSC + SC + MM), as indicators of neck muscle balance. Results: The DHS and the CSM cohort comprised 26 and 52 patients, respectively. Both cohorts had a mean age of 71-year-old. There were no significant differences in the CSAs and most of the indicators of neck balance between the two cohorts. However, the LC/SSC was significantly higher in the DHS cohort than that in the CSM cohort (40.3% and 29.1%, respectively; p < 0.01). Conclusions: Our study highlights a unique anterior-posterior imbalance in the CPM of DHS patients, differing from CSM patients. Strengthening the SSC muscle could be a key to preventing DHS progression.