CHOPIN – Chronic pain neuromodulation

Neuromodulation provides an alternative approach to pain management in cases where less invasive therapies are ineffective or are accompanied with intolerable side effects, and where causal treatment is impossible. Careful selection of indicated patients is therefore a key component of treatment success.

Neuromodulation techniques involve the stimulation of nerve tissue as well as the intraspinal application of drugs. Neurostimulation involves the use of electrical impulses to stimulate the spinal cord or a peripheral nerve; the most widely used techniques involve spinal cord stimulation (SCS), peripheral nerve stimulation (PNS), and peripheral nerve field stimulation (PNFS). Motor cortex stimulation (MCS) is a relatively new technique.

Intraspinal drug delivery systems are implanted pumps that target pain relief or anti-spasm medication to an area of the spine that relays signals between an affected area of the body and the brain. Drugs delivered by these systems are targeted to opioid receptors, which are present in the spinal cord. Subarachnoidally administered drugs mostly involve morphine, or a mixture of local anaesthetics and analgesics. With these systems, medication is immediately released into the fluid surrounding the spinal cord. For this reason, much lower amounts of the active ingredient, such as morphine, are needed than when medication is taken by tablet or intravenous infusion.

Spinal cord stimulation (SCS) affects the transmission of pain by the stimulation of nerve tissue or structures with a defined electric current. Low-voltage electrical stimulation is delivered to the spinal cord, particularly to its collateral nerve fibres, which blocks the sensation of pain. SCS may induce vasodilation, which can be used in the treatment of refractory angina pectoris.

The main effect of peripheral nerve stimulation (PNS and PNFS) is the blockage of sodium channels, which blocks the generation of action potential. The release of GABA, CGRP, substance P, adrenaline, serotonin and alanine probably also contribute to the analgesic effect.

Motor cortex stimulation (MCS) is based on the effect of GABA release and its spread to the limbic system, which attenuates pain.

Neuromodulation techniques are indicated for patients in which other therapeutic options have been exhausted, and causal treatment is impossible. According to the latest trends, a neurostimulation technique should be employed before the patient starts to use opioid analgesics. The most common indications involve neuropathic pain or mixed pain (FBSS, CRBS, phantom pain), or even nociceptive pain in exceptional cases.

The lifespan of generators for neuromodulation systems is rather variable, ranging from 4 to 10 years. For this reason, approximately 40 to 50 generators have to be reimplanted each year. A slight increase in primo-implantations (50 to 60 interventions per year) is expected in the years to come. Together with reimplantations, this could add up to 500–500 implantations over a five-year period.

The CHOPIN project is a multicentre, non-interventional, retrospective and prospective monitoring of patients suffering from chronic pain who underwent an analgesic neuromodulation procedure. The project was initiated by the Czech Pain Society.

Primary objective of the project:

• Monitoring the quality of life in patients who had an neuromodulation analgesic system applied; this will be done during their follow-up at 6-month intervals.

Secondary objective of the project:

• Verifying the pharmacoeconomic benefit of neuromodulation analgesic methods when compared to the standard pharmacological treatment (before the procedure)

Other important information:

• Expert guarantor: Prof Richard Rokyta, MD, PhD
• Partners: eight specialised centres for pain management in the Czech Republic