High Frequency Impulse Therapy for Neuropathic Pain in NMOSD

Neuromyelitis optica spectrum disorder (NMOSD) is a chronic relapsing autoimmune disease of the central nervous system (CNS) that preferentially targets the optic nerves and spinal cord, leading to paralysis, blindness and death. NMOSD is a rare disease that affects approximately 4,000-8,000 (8,000 - 15,000) people in the United States, disproportionately affects non-Caucasians and females, and has a worldwide prevalence estimated to be 0.52 to 4.4/100,000. Pain is a severely disabling component of the disease with up to 91% of patients reporting central neuropathic pain (CNP) characterized by agonizing burning, shooting or tingling sensation in the face, arms, torso and legs. NMOSD lesions in the spinal cord are characteristically long and destructive, and pain is more prevalent in NMOSD than in most other neurological diseases. Research on the impact of persistent pain on quality of life (QoL) in NMOSD has found that those patients with CNP experience more depression, less enjoyment of life, and more difficulty with ambulation. Currently, there is no standard of care for CNP treatment and off-label use of medications typically used for diabetic peripheral neuropathy are often insufficient. NMOSD is a devastating disease and there remains a high unmet need for effective treatment of CNP.

Transcutaneous electrical nerve stimulation (TENS) therapy is a non-invasive pain modifying intervention that utilizes transcutaneous electrical stimulation of ascending (sensory) fibers with the intent of re-organizing maladaptive signaling pathways. This neuromodulatory therapy has been investigated for treatment of persistent peripheral neuropathic pain in several conditions including chemotherapy-induced neuropathy, post-herpetic neuralgia and post-surgical neuropathic pain with promising results. Patients report sustained relief after undergoing daily treatment sessions for 10 consecutive weekdays.

Recently the investigators completed a sham controlled trial using a TENS unit called Scrambler in NMOSD patients showing a meaningful reduction in neuropathic pain compared to controls. The Scrambler device must be operated in an office by a professional technician, thereby limiting its usefulness to the wider NMOSD population. The home TENS device is similar to the Scrambler unit in that it provides non-invasive transcutaneous electrical impulses to reduce pain. It is a small, wearable device that utilizes both high and low frequencies to create a nerve-block effect based on the same gating theory. Because the TENS device for this study is programmable remotely, a controlled trial can be conducted while keeping the patient blinded to the trial arm.

For patients with NMOSD and other conditions that cause pain originating in the central nervous system, non-obtrusive, non-pharmacological devices might prove a viable alternative to pain medications. Pharmaceutical treatments for pain such as opioids have led to addiction and life-style changes with unacceptable side effects. Cost and side effects are concerns with other pharmacologic therapies for pain. In addition, in efforts to control pain, many patients are prescribed multiple medications, and then have to cope with the complexities and hazards of polypharmacy. Most importantly, none of the pharmaceutical treatments for pain in NMOSD have been proven effective in a trial.

If it can be shown among a significant patient cohort that a safe and effective at-home nonpharmacological pain therapy is available for patients with NMOSD, it would be life altering for a great many - not only those with NMOSD, but also with related neuroimmune disorders and other conditions with central neuropathic pain.

The goal of this project is to provide an effective, non-invasive treatment for neuropathic pain in NMOSD that can be safely employed at home. Many NMOSD patients have such chronic pain and/or disability that frequent visits to the clinic for therapy is difficult, if not impossible, in the best of times. Secondly, safe at-home treatments that offer continuous relief of pain (and potentially other co-occurring symptoms) can improve quality of life immensely during this, and likely future times of social distancing, when leaving home is dangerous, especially for a population on lifelong immune suppressants. Also, an at-home therapeutic option will save both time and money for patients.

Inclusion criteria

• Men and women 18 years of age or older diagnosed with NMOSD per the 2015 NMOSD criteria
• Patients must be positive for the aquaporin-4 antibody in serum.
• Presence of persistent neuropathic pain (>3 months) rated at a level of 4 or higher on the Wong-Baker Faces Pain Scale
• Patients must be stable in their disease, such that they have had no spinal cord relapses within 6 months prior to enrollment
• Patients must be on a stable medication regimen that may include anti-epileptic, antidepressant, or non-steroidal anti-inflammatory medications, with no adjustments to the regimen within 30 days of enrollment
• Pain must be localized to a spinal cord lesion
• Patient understands the study regimen, its requirements, risks, and discomforts, and is able and willing to sign an informed consent form

Exclusion criteria

• Patients who are cognitively or mentally incompetent
• Any of the following: pregnant women, nursing women, women of childbearing potential or their sexual partners who are unwilling to employ adequate contraception (condoms, diaphragm, birth control pills, injections, intrauterine device [IUD], surgical sterilization, subcutaneous implants, abstinence, etc.).
• Use of an investigational agent for pain control concurrently or within the past 30 days
• History of an allergic reaction or previous intolerance to transcutaneous electronic nerve stimulation or to latex
• Patients with implantable drug delivery systems, e.g. Medtronic Synchromed.
• Patients with heart stents or metal implants such as pacemakers, automatic defibrillators, cochlear implants, aneurysm clips, vena cava clips and skull plates (Metal implants for orthopedic repair, e.g. pins, clips, plates, cages, joint replacements are allowed)
• Patients with a known history of myocardial infarction or ischemic heart disease within the past six months
• Prior celiac plexus block, or other neurolytic pain control treatment, within 1 month
• Other identified causes of painful parasthesias existing prior to chemotherapy (e.g., carpal tunnel syndrome, B12 deficiency, AIDS, monoclonal gammopathy, diabetes, heavy metal poisoning amyloidosis, syphilis, hyperthyroidism or hypothyroidism, inherited neuropathy, etc.) that might be responsible for the patient's current neuropathic symptoms
• Skin conditions such as open sores that would prevent proper application of the electrodes
• Patients with an ongoing concomitant central neurologic disorder or history of epilepsy, brain damage, or symptomatic brain metastases
• Other medical or other condition(s) that in the opinion of the investigators might compromise the objectives of the study