Motor Cortex Stimulation for Chronic Neuropathic Pain

Inclusion Criteria: * Men and women (non-pregnant) age 21-70 years; * Able to give informed consent in accordance with institutional policies; * Diagnosis of chronic neuropathic pain according to the DN4 Neuropathic Pain Diagnosis scale (score ≥ 4). * Documented pain for at least 12 months; * Documented previous or current treatment for neuropathic pain with medications from at least two of the following groups at adequate doses: antidepressants, anticonvulsants, and/or gabapentinoids; * VAS scores of at least 6 during baselines #1 and 2. * Documented clinical diagnosis of neuropathic pain associated with one of the following conditions: facial pain, post-stroke pain, brachial plexus avulsion, or phantom limb pain of the upper extremities. * In the group with post-stroke pain, only patients with predominant face and upper extremity pain will be included. This will be defined as a difference of ≥ 30% or ≥ 2 points in VAS scores between these regions and lower extremity (in patients who also have pain in the leg). * No change in current neuropathic pain medication regimen for at least 4 weeks prior to study enrollment. * Able to comply with all testing and follow-up requirements as defined by the study protocol. * Must be determined medically stable by surgeon to undergo cortical stimulation surgical procedure. Exclusion Criteria: * Alcohol, medication, or illegal substance dependence or abuse within last 12 months; * Trigeminal neuralgia or atypical facial pain. * Post-stroke pain predominantly in the lower extremity. * Advanced cardiovascular disease which renders anesthesia and surgery as unsafe as determined by neurosurgeon; * Clinically relevant abnormality (e.g. tumor) on study MRI; * Has cardiac pacemaker/defibrillator or other implanted active stimulator; * Has a medical condition requiring a repetitive MRI body scan; * Requires chemotherapy for the treatment of malignancy or requiring chronic oral or intravenous, immunosuppressive, or steroid therapy; * Is unable to comply with study visit schedule and timeline; * Past ablative or relevant intracranial surgery; * A female lactating or of child bearing potential, with a positive pregnancy test or not using adequate contraception; * Other medical conditions likely to require hospitalization within the next year.