Treatment of Upper Limb Chronic Neuropathic Pain by Electrical Stimulation of the Brachial Plexus Nerve Roots

Inclusion Criteria: * Eligibility will be determined by trained clinicians with expertise in chronic pain and neuropathic pain. * Patients between 18 and 80 years old * suffering from moderate to severe (VAS score \>5/10) chronic (duration\> 12 months) neuropathic (DN4 score ≥ 4/10) unilateral pain - located in the upper limb. * from peripheral origin, including complex regional pain syndrome type I and II, post-traumatic or post surgical pain. * refractory to first and second line treatments for neuropathic pain according recent French recommendations and guidelines\[6\], including serotonin- noradrenaline reuptake inhibitor (SNRI) antidepressants (duloxetine and venlafaxine), gabapentin, pregabalin, tricyclic antidepressants, topical lidocaine, high-concentration capsaicin patches, psychotherapy and combinations of them. Patient have signed informed consent \- Patient benefiting from French social insurance system Exclusion Criteria: * Brachial plexus avulsion * Post-zoster neuropathic pain * Phantom limb pain * Patient unable to fill a self-administered questionnaire * Patients with a chronic disease requiring repeated MRI monitoring * Patients with contra-indication to general anesthesia, surgery or percutaneous BP approach. * Patients with other pacemakers (cardiac pacemaker or defibrillator) or patients with a high risk to use a defibrillator due to a known cardiac disorder. * Patients with instable neuropsychological or psychiatric disorders * Vulnerable patients: pregnant or breast feeding, minor, adult under guardianship or deprived freedom