Dorsal Subthalamic Deep Brain Stimulation Improves Pain in Parkinson’s Disease

Abstract

Introduction: Inconsistent effects of subthalamic deep brain stimulation (STN DBS) on pain, a common non-motor symptom of Parkinsons disease (PD), may be due to variations in active contact location relative to a pain-reducing locus of stimulation. Objective: To distinguish the loci of maximal effect for pain and motor improvement in the STN region. Methods: We measured Movement Disorder Society Unified PD Rating Scale (MDS-UPDRS) Part I pain score (item-9), and MDS-UPDRS Part III motor score, preoperatively and 6-12 months after STN DBS. An ordinary least-squares regression model was used to examine active contact location as a predictor of follow-up pain score while controlling for baseline pain, age, dopaminergic medication, and motor improvement. An atlas-independent electric field model was applied to distinguish sites of maximally effective stimulation for pain and motor improvement. Results: In 74 PD patients, mean pain score significantly improved after STN DBS (p = 0.01). In a regression model, more dorsal active contact location was the only significant predictor of pain improvement (R2 = 0.17, p = 0.03). The stimulation locus for maximal pain improvement was lateral, anterior, and dorsal to that for maximal motor improvement. Conclusions: More dorsal STN DBS improves pain. Stimulation of the zona incerta, a region known to modulate pain in humans, may explain this observation.