The Effect of Transcranial Direct Current Stimulation (t-DCS) On the P300 Component of Event-Related Potentials in Patients With Chronic Neuropathic Pain Due To CRPS or Diabetic Neuropathy

Inclusion Criteria: * An affected upper limb or lower limb * Diagnosed as : Diabetic neuropathy, Complex Regional Pain Syndrome (CRPS), Chemotherapy Induced Pain Neuropathy (CIPN), Peripheral Neuropathy. * Have not responded to at least two medications of the following groups: Opioids. Tricyclics, SSRI, SNRI, Pregabalin, Gabapentin, Anticonvulsants. * Positive LANSS or CRPS criteria as follows: 1. Continuing pain which is disproportionate to any inciting event or for CRPS diagnosis. 2. Must report at least one symptom (symptoms here are reports by subject) in each of the four following categories: sensory, vasomotor, sudomotor/edema, motor/trophic. 3. Must display at least one sign (signs here refer to objective observation/testing) in in each of the four following categories: sensory, vasomotor, sudomotor/edema, motor/trophic; * Must meet resistant neuropathic pain criteria - pain that is neuropathic in characters that at least two neuropathic medications not from the same group have been tried for at least a month without improvement or severe side-effects were experienced. Resistant neuropathic pain with a score for "average pain in the last 24 hours" ≥4 on a numeric scale 0-10 * tDCS naive Exclusion Criteria: * Serious health problems other than CRPS or resistant neuropathic pain (e.g. uncontrolled hypertension, uncontrolled diabetes, heart failure) * Pain/painful conditions unrelated to CRPS or neuropathic pain * Pregnancy * History of seizures/epilepsy * Implanted device (e.g. pacemaker) * Active illicit drug/alcohol abuse * Unable to follow directions or complete tools in Hebrew * Previous exposure to tDCS stimulation