Refractory Pain Management in Amyloid-Associated Peripheral Neuropathy:

Scrambler therapy: A ray of hope for refractory chemotherapy-induced peripheral neuropathy

Scrambler therapy (ST) is a novel noninvasive modality for treatment of chronic neuropathic and cancer pain using 5 artificial neurons. The principle with Scrambler Therapy is that synthetic "non-pain" information is transmitted by C fiber surface receptors. Chemotherapy-induced peripheral neuropathy can markedly deteriorate patient's quality of life and can also negatively affect compliance with the anticancer treatment. Chronic neuropathic pain presents a therapeutic challenge if resistant to pharmacological management opioids and other types of treatments. We have described here successful use of scrambler therapy in three cases of chemotherapy-induced peripheral neuropathy.

Inside the Scrambler Therapy, a Noninvasive Treatment of Chronic Neuropathic and Cancer Pain: From the Gate Control Theory to the Active Principle of Information

Scrambler therapy (ST) is an electro-analgesia therapy for the noninvasive treatment of chronic neuropathic and cancer pain based on a new generation of medical device that uses 5 artificial neurons and is based on a novel theoretical model the differs from gate control theory. The active principle with Scrambler Therapy is such that synthetic "non-pain" information is transmitted by C fiber surface receptors. This is a different theoretical mechanism than the traditional electric stimulation of A-Beta fibers to produce paresthesia and/or block the conduction of nerve fibers to produce an analgesic effect, that is, via TENS (transcutaneous electrical nerve stimulation) machines. Scrambler therapy was developed to treat chronic neuropathic pain and cancer pain resistant to opioids and other types of treatments. The goal of Scrambler Therapy is to eliminate pain during treatment and allow for long-lasting analgesia after a series of 10 to 12 consecutive treatments performed over a 2-week period. The aim of this review is to clarify the underlying theory of Scrambler Therapy and describe the appropriate usage method that maximizes its effectiveness while reducing bias and deepen the explanation of the artificial neuron technology associated with Scrambler Therapy.

Why mu-opioid agonists have less analgesic efficacy in neuropathic pain?

Injury to peripheral nerves often leads to abnormal pain states (hyperalgesia, allodynia and spontaneous pain), which can remain long after the injury heals. Although opioid agonists remain the gold standard for the treatment of moderate to severe pain, they show reduced efficacy against neuropathic pain. In addition to analgesia, opioid use is also associated with hyperalgesia and analgesia tolerance, whose underlying mechanisms share some commonalities with nerve injury-induced hypersensitivity. Here, we reviewed up-to-day research exploring the contribution of mu-opioid receptor (MOR) on the pathophysiology of neuropathic pain and on analgesic opioid actions under these conditions. We focused on the specific contributions of MOR populations at peripheral, spinal and supraspinal level. Moreover, evidences of neuroplastic changes that may underlie the low efficacy of MOR agonists under neuropathic pain conditions are reviewed and discussed. Sensitization processes leading to pain hypersensitivity, molecular changes in signalling pathways triggered by MOR and glial activation are some of these mechanisms elicited by both nerve injury and opioid exposure. Nerve injury-induced pain hypersensitivity might be masking the initial analgesic effects of opioid agonists, and alternatively, sustained opioid treatment to individuals already suffering from neuropathic pain could aggravate their pathophysiological state. Finally, some combined therapies that can increase opioid analgesic effectiveness in neuropathic pain treatment are highlighted. SIGNIFICANCE: This review provides evidence of the low benefit of opioid monotherapy in neuropathic pain and analyses the reasons of this reduced effectiveness. Opioid agonists along with drugs targeted to block the sensitization processes induced by MOR stimulation might result in a better management of neuropathic pain.