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

Abstract

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.