title: Evaluation of a home-based transcranial direct current stimulation (tDCS) treatment device for chronic pain: study protocol for a randomised controlled trial.
abstract: BACKGROUND
  Stimulation of the primary motor cortex (M1) has been shown to reduce the pain of neuropathy in multiple studies. There are several methods of stimulation both invasive and non-invasive. Recent work by this laboratory has seen that 40% of a sample of chronic neuropathic pain patients responded positively to non-invasive repetitive transcranial magnetic stimulation (rTMS) to the motor cortex with a reduction in pain levels by at least 20%. The effect however is short lived and multiple return visits are necessary to maintain this response. Transcranial direct current stimulation (tDCS) offers a more mobile method of motor cortex stimulation and is similarly non-invasive. The protocol described is designed to assess the analgesic effect of a home-based tDCS treatment device on chronic neuropathic pain in both responders and non-responders to previous TMS treatment.
  
  
  METHODS
  This article reports the protocol for a randomised, sham-controlled, double-blinded crossover study in which patients with chronic neuropathic pain (n = 24) will receive anodal, cathodal and sham tDCS over M1. All patients will have previously completed a study of rTMS of the motor cortex and have been designated as responders or non-responders to this modality. Patients receive all three tDCS stimulation types by self-administration. We assess the effect on pain scores [numerical rating scale (NRS)], self reported health status (Short Form-36 Health Survey) and anxiety/depression (Hospital Anxiety and Depression Scale). A linear mixed model with fixed effects will analyse changes in pain scores from pre- to post- interventions. Analysis will be carried out on an intention-to-treat basis. A proportion analysis will also be carried out with patients separated into either responders or non-responders to previous TMS. Safety will be assessed throughout the study by monitoring of adverse events.
  
  
  CONCLUSIONS
  The result of this trial will assess the efficacy of self-administered tDCS of the motor cortex in the treatment of chronic neuropathic pain and also provide insight into whether a potential differential effect is seen in patients that have previously been shown to be either responsive or non-responsive to rTMS over the same area.
  
  
  BACKGROUND
  ISRCTN56839387 date 27 January 2014. First patient randomised to trial 30 October 2012.
authors.affiliation: Pain Research Institute, Clinical Sciences Centre, Lower Lane, Fazackerley, Liverpool, L9 7AL, UK. foneill@liv.ac.uk.|Department of Oral Surgery, Liverpool University Dental Hospital, Pembroke Place, Liverpool, L3 5PS, UK. foneill@liv.ac.uk.
authors.forename: Francis
authors.initials: F
authors.lastname: O'Neill
authors.affiliation: Pain Research Institute, Clinical Sciences Centre, Lower Lane, Fazackerley, Liverpool, L9 7AL, UK. psacco@liv.ac.uk.
authors.forename: Paul
authors.initials: P
authors.lastname: Sacco
authors.affiliation: Pain Research Institute, Clinical Sciences Centre, Lower Lane, Fazackerley, Liverpool, L9 7AL, UK. tjn@liv.ac.uk.
authors.forename: Turo
authors.initials: T
authors.lastname: Nurmikko
mesh_terms: D059350:Chronic Pain / Q000628:therapy*; D002985:Clinical Protocols; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006801:Humans; D018401:Sample Size; D065908:Transcranial Direct Current Stimulation / Q000295:instrumentation*