Characteristics of sagittal spinopelvic alignment in patients with Parkinson’s disease presenting with dropped head syndrome: a case series study

BACKGROUND: Dropped head syndrome (DHS) is a rare specific abnormal posture known to develop in Parkinson’s disease (PD). This case series study aimed to characterize DHS by analyzing the characteristics of sagittal spinopelvic alignment in patients with PD/DHS. METHODS: The study included eight patients with PD/DHS (men = 3, women = 5; mean age, 68.1 ± 6.4 years). Sagittal spinopelvic alignment was evaluated using 10 parameters on whole-spine lateral radiographs. RESULTS: The time from the onset of PD to that of DHS varied among the patients from 0 to 15.3 years. In three patients, DHS appeared before the diagnosis of PD. The severity of motor symptoms at DHS onset varied from modified Hoehn and Yahr stage 1 to 4 among the patients. Although the spinopelvic parameters differed among PD/DHS individuals, all patients exhibited cervical kyphosis (cervical lordosis < 0˚). In patients with a larger T1 slope and greater thoracic kyphosis, anterocollis tended to be more severe. According to the assessment of the sagittal vertical axis (SVA), half of the patients showed a positive SVA (SVA ≥ 0 mm), whereas the other half showed a negative SVA (SVA < 0 mm). CONCLUSION: DHS appeared regardless of the duration or severity of PD. Although all patients with PD/DHS exhibited cervical kyphosis, the C7 plumb line was shifted anteriorly in half of the patients and posteriorly in the other half.