title: Neuropathic pain: transcranial electric motor cortex stimulation using high frequency random noise. Case report of a novel treatment.
abstract: OBJECTIVE
  Electric motor cortex stimulation has been reported to be effective for many cases of neuropathic pain, in the form of epidural stimulation or transcranial direct current stimulation (tDCS). A novel technique is transcranial random noise stimulation (tRNS), which increases the cortical excitability irrespective of the orientation of the current. The aim of this study was to investigate the effect of tRNS on neuropathic pain in a small number of subjects, and in a case study explore the effects of different stimulation parameters and the long-term stability of treatment effects.
  
  
  METHODS
  THE STUDY WAS DIVIDED INTO THREE PHASES: (1) a double-blind crossover study, with four subjects; (2) a double-blind extended case study with one responder; and (3) open continued treatment. The motor cortex stimulation consisted of alternating current random noise (100-600 Hz), varying from 0.5 to 10 minutes and from 50 to 1500 μA, at intervals ranging from daily to fortnightly.
  
  
  RESULTS
  One out of four participants showed a strong positive effect (also compared with direct-current-sham, P = 0.006). Unexpectedly, this effect was shown to occur also for very weak (100 μA, P = 0.048) and brief (0.5 minutes, P = 0.028) stimulation. The effect was largest during the first month, but remained at a highly motivating level for the patient after 6 months.
  
  
  CONCLUSIONS
  The study suggests that tRNS may be an effective treatment for some cases of neuropathic pain. An important result was the indication that even low levels of stimulation may have substantial effects.
authors.affiliation: Department of Neuroscience, Uppsala University, Uppsala, Sweden.
authors.forename: Per A
authors.initials: PA
authors.lastname: Alm
authors.forename: Karolina
authors.initials: K
authors.lastname: Dreimanis
keywords: central pain; motor cortex stimulation; neuropathic pain; random noise stimulation; transcranial direct current stimulation