[Using electricity to combat headache : Electrotherapy and tDCS in the 1870s/1880s and today].

Headache can be a widespread symptom as well as a disorder in itself. Headache syndromes such as migraine cause a lot of distress, disability and overall socioeconomic costs. Pharmacological treatments are often limited in their efficacy as well as due to side effects. The therapeutic application of electricity for this medical indication was a relevant field of research in the 19th century and-in the form of transcranial direct current stimulation (tDCS)-is still widely studied today. This paper provides an overview of publications from the late 19th century (as the era of discovery and success of electrotherapy) as well as contemporary studies investigating the usage of weak currents for the treatment or prophylaxis of headache. Our results show a large number of highly favorable reports of treatment successes. However, the number of cases analysed is often rather small and the forms of electric stimulation applied were often highly heterogeneous. In summary, electric stimulation appears to be a promising field of research and a possible therapeutic agent for the treatment of headaches; however, further research is necessary, especially into the details of the stimulation techniques applied and the various indications in which it may be of use.