Depolarising Electrical Skin Stimulation in Neuropathic and Postoperative Pain

Study Overview
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Brief Summary
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The aim of the study is to evaluate voltage gated sodium channel (NaV1.7) dependent pain phenomena in neuropathic pain and chronic postoperative pain.

Detailed Description
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Sinus-like electrical stimulation may depolarize unmyelinated skin nociceptors involving NaV1.7 channels. In this case electrical stimulation may provoke pain already with very low currency intensity which normally not provoke pain in healthy subjects. This may be predictive for pain relief due to the sodium channel blocker lidocaine 5% patch. The study will characterize pain states in peripheral neuropathic pain as well as within the painful scar in chronic postoperative pain with regard to the involvement of NaV1.7 channels. In addition, the pain site in chronic postoperative pain (scar) will be characterized by laser-evoked potentials (LEP) and quantitative sensory testing (QST). Pain related questionnaires will be obtained.

Official Title
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Selective Activation of Unmyelinated Skin Nerve Fibres Using Slow Depolarising Transcutaneous Electrical Stimulation in Patients With Neuropathic Pain or Chronic Postoperative Pain

Conditions
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Neuropathy;Peripheral

Intervention / Treatment
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* Diagnostic Test: neurophysiology


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Group (1) patients with neuropathic pain Group (2) patients with chronic postoperative pain Exclusion Criteria (both Groups): severe psychiatric disorder requiring hospitalisation in the past any neurological disease other than the pain diagnosis

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| chronic pain<br>individuals suffering from chronic pain | Diagnostic Test: neurophysiology<br>* electrophysiologic measurements of peripheral nerves<br>|
| neuropathic pain<br>individuals suffering from neuropathic pain | Diagnostic Test: neurophysiology<br>* electrophysiologic measurements of peripheral nerves<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in pain intensity | numeric rating scale (NRS), rating from 0-10, 0=no pain, 10=maximum pain imaginable | at baseline and during electric nerve stimulation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| heat pain threshold | Ramped stimuli (+1 degree Celsius / sec) that are terminated when the subject presses a button. | baseline | 
| cold pain threshold | Ramped stimuli (-1 degree Celsius / sec) that are terminated when the subject presses a button. | baseline | 
| mechanical detection threshold | Fine plastic hairs with different bending forces are applied to the skin to determine the mechanical detection threshold. | baseline | 
| mechanical pain threshold | Differently weighted pinprick stimuli are applied at a rate of 2sec on and 2sec off in an ascending order until the first percept of sharpness is reached. | baseline | 
| mechanical pain sensitivity | Differently weighted pinprick stimuli are applied to obtain a stimulus- response function for pinprick-evoked pain. Subjects were asked to give a pain rating for each stimulus (rating from 0-10, 0=no pain, 10=maximum pain) | baseline | 
| dynamic mechanical allodynia | Different stimuli, tactile and pinprick are applied with the subject giving numerical pain ratings for each stimulus (rating from 0-10, 0=no pain, maximum pain). | baseline | 
| vibration detection threshold | Tuning fork is placed over a bony prominence until the subject cannot not feel vibration any more. | baseline | 
| pressure pain threshold | A pressure gauge that exerts forces of ascending stimulus intensities is applied as a slowly increasing ramp over a muscle. | baseline | 
| LEP latency | latency of N2 and P2 components of laser evoked potential signal curve | baseline | 
| LEP amplitude | amplitude of laser evoked potential signal curve | baseline | 
| stadium of pain chronification | assessment of the stadium of pain chronification (stadium 1-3) using standardized questionnaire | baseline | 
| pain severity | assessment of pain severity (grade 1-4) using the Chronic Pain Grading Questionnaire | baseline | 
| physical health status | assessing the physical health status using the Short Form-12 questionnaire | baseline | 
| mental health status | assessing the mental health status using the Short Form-12 questionnaire | baseline | 
| anxiety | assessing anxiety using the Hospital Anxiety and Depression Scale questionnaire | baseline | 
| depression | assessing Depression using the Hospital Anxiety and Depression Scale questionnaire | baseline | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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neuropathic pain, chronic postoperative pain