Spinal compensation patterns in dropped head syndrome according to prone-position cervical extension performance

Dropped Head Syndrome (DHS) is caused by muscle weakness of the cervical extensor muscles (CEM), resulting in global imbalance. However, the relationship between CEM weakness and sagittal spinal alignment remains unclear. The purpose of this study was to investigate the correlation between CEM weakness and global spinal posture in patients with DHS.

The subjects were 159 patients diagnosed with DHS. CEM was evaluated by cervical extension performance in the prone position, and the subjects were classified into Mild DHS (MMT≥3; 33 subjects) and Severe DHS (MMT<3; 126 subjects). Sagittal spinal alignment was measured by standing whole-body radiography, and correlations between the parameters were analyzed individually.

Both DHS groups had a positive correlation between CBVA (chin- brow vertical angle), C-SVA (cervical sagittal vertical axis) and TK (Thoracic kyphosis angle). In Mild DHS, T1S (T1 slope angle) showed a positive correlation with TK (thoracic kyphotic angle) but not with PT (pelvic tilt angle), while T1S of Severe DHS showed a positive correlation with TK as well as with PT.

CEM weakness affected the global sagittal spinal posture in patients with DHS. In CEM with MMT< 3, the compensation of head drop was lost to thoraco-lumbar segments, and the head imbalance was compensated for by the pelvic posterior tilt.