Central pain processing in “drug-naïve” pain-free patients with Parkinson's disease

Abstract

Background: Despite its clinical relevance, the pathophysiology of pain in Parkinson's disease (PD) is still largely unknown, and both central and peripheral mechanisms have been invoked. Objectives: To investigate whether central pain processing is altered in “drug-naive” pain-free PD (dnPD) patients. Methods: Using event-related functional MRI (fMRI), functional response to forearm heat stimulation (FHS) at two different intensities (41°C and 53°C) was investigated in 20 pain-free dnPD patients, compared with 18 healthy controls (HCs). Secondary analyses were performed to evaluate associations between BOLD signal changes and PD clinical features and behavioral responses. Results: During low-innocuous FHS (41°C), no activation differences were found between dnPD patients and HCs. During high-noxious FHS (53°C) a significantly increased activation in the left somatosensory cortex, left cerebellum, and right low pons was observed in dnPD patients compared to HCs. In the latter experimental condition, fMRI BOLD signal changes in the right low pons (p