title: A randomised, patient-assessor blinded, sham-controlled trial of external non-invasive peripheral nerve stimulation for chronic neuropathic pain following peripheral nerve injury (EN-PENS trial): study protocol for a randomised controlled trial.
abstract: Eight percent of people in the UK are estimated to have persistent (chronic) neuropathic pain, and for many there is no effective treatment. Medications are the most common first-line treatment but often have limited benefit or adverse events. Surgical treatments, such as spinal cord stimulation, are then often considered. External non-invasive peripheral nerve stimulation (EN-PENS) is a form of electrical stimulation that involves placing a pen-shaped electrode onto the skin, which can be easily self-administered by patients. Observational studies suggest that EN-PENS may relieve pain for people with localised neuropathic pain; however, there is currently no evidence from controlled trials to confirm the efficacy and confidently determine the effect size for patients with longstanding neuropathic pain.
  
  
  
  EN-PENS is a single-site, blinded, randomised controlled parallel-group superiority add-on trial with a 1:1 allocation ratio, designed to evaluate the efficacy of treatment versus control treatment in 76 patients with longstanding neuropathic pain following peripheral nerve injury. Patients with moderate to -severe neuropathic pain following peripheral nerve injury will be randomised to receive either the active or control treatment, followed by an optional treatment extension or treatment switch to the alternative treatment arm. The primary outcome is average 24-h pain intensity recorded on an 11-point (0-10) numerical rating scale, averaged over the last 7 days of treatment.
  
  
  
  Study results will be used to inform potential treatment efficacy and cost-effectiveness of EN-PENS for this population group.
  
  
  
  ISRCTN53432663 . Registered on 7 July 2016.
authors.affiliation: The Walton Centre NHS Trust, Liverpool, UK. selina.johnson@thewaltoncentre.nhs.uk.|The University of Liverpool, Liverpool, L69 3BX, UK. selina.johnson@thewaltoncentre.nhs.uk.
authors.forename: Selina
authors.identifier: 0000-0001-8788-4512
authors.initials: S
authors.lastname: Johnson
authors.affiliation: The Walton Centre NHS Trust, Liverpool, UK.|The University of Liverpool, Liverpool, L69 3BX, UK.
authors.forename: Andreas
authors.initials: A
authors.lastname: Goebel
authors.affiliation: The Walton Centre NHS Trust, Liverpool, UK.
authors.forename: Roberta
authors.initials: R
authors.lastname: Richey
authors.affiliation: Centre for Health Economics and Medicines Evaluation, Bangor University, Bangor, Gwynedd, LL57 2PZ, UK.
authors.forename: Emily
authors.initials: E
authors.lastname: Holmes
authors.affiliation: Centre for Health Economics and Medicines Evaluation, Bangor University, Bangor, Gwynedd, LL57 2PZ, UK.
authors.forename: Dyfrig
authors.initials: D
authors.lastname: Hughes
mesh_terms: D059350:Chronic Pain / Q000628:therapy*; D002985:Clinical Protocols; D004599:Electric Stimulation Therapy; D006801:Humans; D009437:Neuralgia / Q000628:therapy*; D017063:Outcome Assessment, Health Care; D059348:Peripheral Nerve Injuries / Q000150:complications / Q000628:therapy*; D018401:Sample Size
keywords: Chronic pain; External non-invasive peripheral nerve stimulation; Neuropathic pain; Peripheral nerve injury