Neuropathic pain results from damage to or dysfunction of the peripheral or central nervous system, rather than stimulation of pain receptors. Diagnosis is suggested by pain out of proportion to tissue injury, dysesthesia (eg, burning, tingling), and signs of nerve injury detected during neurologic examination. Although neuropathic pain responds to opioids, treatment is often with adjuvant drugs (eg, antidepressants, anticonvulsants, baclofen, topical drugs). Neuropathic pain (e.g. phantom limb pain, CRPS, postherpetic neuralgia, postsurgical pain syndromes, CLBP etc.) remains a challenging condition to treat because it is commonly refractory to classical pharmacological and to surgical treatment approaches. Chronic low back pain (CLBP) is a widespread and costly problem for which few interventions are effective. An increased focus on the study of the nervous system and its involvement in pain disorders has documented complex neuronal activity and structural changes at a peripheral, as well as at spinal cord and cortical levels indicating a neuropathic element in CLBP. Accumulated evidence suggests that neuropathic pain in general and CLBP specifically might be associated to brain cortical plastic changes. Thus an ideal rehabilitative approach should aim to reverse them. In line with this idea, the investigators suggest an innovative noninvasive intervention aimed at alleviating neuropathic pain. New rehabilitative approaches have been proposed to try and reverse this cortical reorganization. Results of several studies have shown that motor cortex stimulation with epidural electrodes or repetitive transcranial magnetic stimulation (rTMS) or transcranial direct stimulation (tDCS) are effective in reducing pain in patients with central pain refractory to treatment. Transcranial direct current stimulation (tDCS) is an easily applied and safe technique by which brain activity can be modulated noninvasively and can decrease pain in patients with refractory central pain. The investigators hypothesized that focal-tDCS treatment personally customized to each patients basal neuronal network properties would result in both acute and long term pain relief for neuropathic pain patients.

Inclusion Criteria:

1. age 18 to 70
2. CLBP as defined by the European guidelines

Exclusion Criteria:

1. Acute low back pain (duration of less than 6 months
2. Neurological illness causing structural brain damage (e.g. Stroke, TIA)
3. Psychiatric disease other than mood disorders
4. Current chronic use of medications with pro-epileptic properties
5. Known alcohol dependency
6. Use of alcohol within the previous 24 hours
7. History of loss of consciousness
8. Epilepsy or epilepsy in a first degree relative
9. Medical implants
10. Pregnancy
11. Illicit drug use or within the previous month