Rates and Predictors of Pain Reduction with Intracranial Stimulation for Intractable Pain Disorders

Introduction: Intracranial stimulation paradigms, namely deep brain stimulation (DBS) and motor cortex stimulation (MCS), have been used to treat intractable pain disorders. However, treatment efficacy remains heterogeneous, and factors associated with pain reduction are incompletely understood. A updated meta-analytical synthesis combining DBS and MCS studies using modern stimulation systems is warranted to quantitatively assess prognostic factors influencing pain outcomes.

Methods: We performed quantitative and comprehensive systematic literature review of pain outcomes (visual analogue scale, quality of life (QOL) measures, complications, pulse generator implant rate, explant or cessation of stimulation) after implantation of modern DBS or MCS devices by obtaining individual patient data. We evaluated 663 patients from 36 study groups, and stratified outcomes by pain etiology and implantation targets.

Results: Included studies were all observational in nature, and no randomized, controlled trials were identified. MCS patients had higher trial success rate compared to DBS patients (90% vs 83%; P = 0.027), while patients with peripheral pain had higher trial success rate compared to patients with central pain (90% vs 83%; P = 0.022). Complication rates were similar for MCS and DBS patients (12% vs 15%). Rates of explant or cessation of stimulation across MCS and DBS patients and patients with central versus peripheral pain were similar. Of all implanted patients, mean pain reduction at last follow-up was 45.8% (95% CI: 40.3-51.2) with a 28.7% (95% CI: 9.2-48.1) improvement in QOL. No difference was seen between MCS patients (43.8%; 95% CI: 36.7-58.2) and DBS patients (48.6%; 95% CI: 39.2-58) or central (41.2%; 95% CI: 34.3-48.0) and peripheral etiologies (45.5%; 95% CI: 37.7-53.3). Multivariate analysis identified PAG/PVG target to be associated with worse short-term pain reduction while spinal cord injury was associated with worse long-term pain reduction.

Conclusion : Both DBS and MCS have similar efficacy and complication rates in the treatment of intractable pain syndromes. Patients with central pain syndromes tended to have lower trial success. Additional prognostic factors include PAG/PVG targeting and diagnosis of spinal cord injury.