Cervical Muscle Composition in Degenerative Dropped Head Syndrome: A Propensity Score Matching Study.

Abstract

Retrospective cross-sectional. To compare cervical muscle composition in patients with non-neuromuscular DHS caused by degenerative disease of the cervical spine to patients without DHS who underwent anterior cervical discectomy and fusion (ACDF). Dropped head syndrome (DHS) is characterized by severe weakness of the cervical paraspinal muscles, particularly of the neck extensors, that leads to a chin-on-chest deformity. This forward flexion prevents them from lifting their heads against gravity or maintaining a forward gaze, resulting in gait disturbance and impairment in activities of daily life. Propensity score matching was conducted, calculated based on age, sex, and BMI, to compare cervical muscle fat infiltration (FI) across 3 groups: (1) Patients with DHS, (2) Non-DHS patients who underwent 1 to 2 level ACDF, and (3) Non-DHS patients who underwent 3 or more levels of ACDF. The cervical muscles were segmented on axial T2 MRI from C3 to C7, and the percentage FI was measured using a previously validated Matlab software. Patients with DHS showed significantly higher FI in the anterior muscle group compared with those undergoing ACDF at all levels ( P < 0.005) except for C3 ( P = 0.243). At all levels, patients with DHS demonstrated significantly higher FI in the posterolateral ( P < 0.001), posteromedial ( P < 0.01), scalenus ( P < 0.01), and trapezius muscle groups ( P < 0.005). At the C4 level, DHS patients had significantly higher FI in the sternocleidomastoid muscle group compared with ACDF groups ( P = 0.005). This study is the first to quantify FI in the cervical muscles of DHS patients without neurodegenerative/neuromuscular disease. DHS patients showed significant muscular decompensation, with pronounced atrophy in both extensor and anterior muscles compared with ACDF groups. Further studies are needed to explore these relationships and evaluate muscle in DHS with neurodegenerative conditions.