The purpose of this study is to evaluate the efficacy of cortical stimulation (CS) as an adjunctive treatment for chronic neuropathic pain.

Prospective, controlled, double blind, randomized, crossover study with endpoint evaluations at the end of each 3-month treatment period.

An interim analysis will be conducted by a blinded committee when approximately half of the patients have finished the study.

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.