Quantitative evaluation of cervical extensor muscles in dropped head syndrome patients using contrast-enhanced magnetic resonance imaging

Study Design: Retrospective observational study. Objectives: To quantitatively assess contrast enhancement in five cervical extensor muscles in patients with dropped head syndrome (DHS) using gadolinium-enhanced magnetic resonance imaging (MRI), and to explore potential pathophysiological mechanisms based on enhancement patterns. Background: Dropped head syndrome (DHS) impairs forward gaze, significantly affecting daily activities and quality of life. Although MRI has proven useful in evaluating cervical extensor muscle dysfunction, a standardized quantitative analysis of contrast enhancement has not yet been established. Materials and Methods: Twenty-two patients with DHS and 20 control subjects without DHS underwent gadolinium-enhanced cervical MRI. Signal intensity was measured in five posterior neck muscles: trapezius, splenius capitis, rhomboid minor, semispinalis cervicis, and levator scapulae. Signal-to-noise ratios (SNR) and intensity ratios (IR), originally defined, were calculated and compared between the two groups. Results: The DHS group showed significantly higher SNR values in all five muscles compared with the control group, with the most pronounced differences observed in the splenius capitis and rhomboid minor ( P < 0.01). The splenius capitis also demonstrated significantly higher IR values than the trapezius and levator scapulae ( P < 0.05), indicating distinct enhancement patterns. Conclusions: Contrast-enhanced MRI revealed characteristic enhancement in the splenius capitis and rhomboid minor muscles in patients with DHS, suggesting inflammatory changes at the C6/C7 spinous process attachments. Milder enhancement in other extensor muscles may reflect stress-related changes due to cervical extension. The variability in rhomboid minor enhancement suggests the existence of pathophysiological subtypes within DHS.