Central Mechanisms of Calmare: an fMRI Trial

Pain can be either useful or harmful. Acute pain conveys information to the brain about real or potential damage that can productively lead to avoidance or treatment of the damage. However, chronic pain, which extends beyond these useful purposes, becomes a potentially debilitating inconvenience. Estimations based on surveys report that as many as 33% of Americans suffer from chronic pain, with a significant portion being unable to successfully manage it.

The current means to treating chronic pain include: surgery, drug therapy, physical therapy, psychological intervention, and others. Unfortunately, despite these options, many people continue to suffer from a chronic pain condition. Neuropathic pain, or pain caused by nervous system damage, is particularly hard to treat. Drug therapy and surgery have relatively low success rates and undesirable side effects. Thus, there is a need for additional research and new treatment methods for neuropathic pain patients.

The Calmare device was designed as one such means to treat chronic neuropathic pain. It works through electrostimulation of the skin near the pain site, and, according to recent studies, has significantly reduced chronic neuropathic pain in most subjects (Majithia et al., 2016).

Previous studies of Calmare effectiveness have defined the success of treatment as the reduction of reported pain levels by the patient. Though useful, these studies fail to provide an objective measurement of pain reduction and fail to discover the mechanisms by which it occurs. In addition, previous studies have been unable to perform a true double-blind experiment in which the placebo effect was entirely accounted for. The pilot study takes a step toward filling this gap by performing a double blind, randomized single-treatment trial comparing Calmare efficacy to traditional transcutaneous electrical nerve stimulation (TENS) efficacy. The ten-treatment study examines the durability of the pain relief for 12 weeks after the treatment period.

The goal of these studies is two-fold: first, to use fMRI before and after a full therapeutic Calmare treatment course to determine the extent to which Calmare affects the connectivity of the pain centers of the brain, and second, to determine whether traditional TENS or Calmare is more effective in reducing neuropathic chronic pain. The Calmare treatment is administered in a double-blind fashion with neither the technician, nor the subject knowing whether the TENS or the Calmare is being administered. The investigator's hypothesis is that Calmare therapy decreases subject pain through a central mechanism that will be manifest in decreased functional connectivity of the brain's pain centers. The degree to which this happens is determined by comparing the decrease in pain intensity, as reported by the patient, with the difference in fMRI BOLD temporal correlations between pain centers.

Inclusion criteria

• They must have suffered from a diagnosed peripheral neuropathy (diabetic, chemotherapy induced, or other) for a minimum of 6 months.
• At the time of the study they must experience pain greater than or equal to 5 on a visual analog pain scale from 0-10, with 0 being "no pain" and 10 being "the worst imaginable pain."

Exclusion criteria

• pregnancy
• a history of epilepsy or brain damage
• presence of a serious psychiatric disorder (e.g. schizophrenia, manic-depressive psychosis, primary major depression)
• multiple sources of chronic pain (e.g. a chronic pain condition other than a peripheral neuropathy or more than one site of neuropathies)
• a skin condition that would prevent application of skin electrodes
• latex allergy
• severe arrhythmia or any form of equivalent heart disease
• history of myocardial infarction or ischemic heart disease within the past 6 months
• celiac plexus block or other neurolytic pain control treatment within the past 4 weeks
• state of active withdrawal from drugs and/or alcohol
• ineligible for fMRI due to metal implants, etc.