Supplementary Material for: Rare abdominal manifestations in a patient with Parkinson’s disease after deep-brain stimulation of the subthalamic nucleus: A case report

Introduction Abdominal pain is an occasionally observed non-motor symptom during “off” periods in Parkinson’s disease (PD), often associated with End-of-Dose Wearing-Off (EODWO). However, severe abdominal manifestations such as painful abdominal contraction (PAC) are rare, and their pathogenesis remains unclear. We report a unique case in which both PAC and belly dancer’s dyskinesia (BDD) emerged following subthalamic nucleus deep-brain stimulation (STN-DBS). Case Presentation A 74-year-old woman with PD underwent bilateral STN-DBS. Following a postoperative reduction in her levodopa dosage, she developed continuous abdominal pain with a downward-pulling sensation, which was diagnosed as PAC. Symptoms worsened in upright positions and improved supine. With an increase in STN-DBS stimulation intensity, she subsequently developed wave-like involuntary contractions of the abdominal wall muscles, consistent with BDD, while her PAC remained unchanged. STN-DBS adjustments and dopaminergic agents other than levodopa provided only partial relief, with PAC showing minimal improvement. Restoration of the preoperative levodopa dosage led to marked alleviation of PAC. Additional STN stimulation effectively managed recurrent EODWO-related pain. Four months postoperatively, motor symptoms improved significantly, with only mild peak-dose BDD remaining. Conclusion This case illustrates that PAC may result from reduced baseline dopamine levels and may not respond to STN-DBS alone. The co-occurrence of PAC and BDD suggests a complex interplay between motor and non-motor circuits, possibly involving spinal plasticity and central pattern generators. Clinicians should consider that some cases of severe abdominal pain in Parkinson’s disease may represent distinct non-motor phenomena that appear to respond preferentially to levodopa administration.