The purpose of the study is to evaluate the efficacy of the transcranial direct current stimulation of the primary motor cortex (M1) in patients affected by refractory chronic migraine (coded as 1.5.1 in the international headache classification 2nd edition, 2004) and medication-overuse headache (coded as 8.1) with migraine as primary headache.

Inclusion Criteria:

• Chronic MIgraine or Medication Overuse Headache according to the diagnostic criteria set out in the 2nd edition of the International Classification of Headache Disorders refractory to treatment according to the Refractory Headache Special Interest Section of the American Headache Society (Schulman et al., 2008)

Exclusion Criteria:

• Other primary or secondary headaches.
• Any serious systemic or neurological disease or psychiatric disorder.
• Pregnancy or breastfeeding
• Previous or current use of other or similar devices for pain control
• Heart conduction and rhythm disorders
• Cranial surgery
• Other pain conditions, accordingly with current guidelines