Pain experts discuss new frontiers in neuromodulation at conference

The International Neuromodulation Society (INS) recently held their 4^th Scientific Meeting entitled Neuromodulation: New Frontiers.

The INS is a non-profit group comprising clinicians, scientists and engineers whose aim is the scientific development and awareness of neuromodulation. Neuromodulation refers to the process in which chemicals can signal and regulate neurons (nerve cells) in the body.

The theme of the New Frontiers meeting is the increasing technology within the industry. The increasing technology is offering new treatments for many disorders whose ailments have previously not been relieved by conventional treatments.

The meeting was chaired by Dr Rick Acland and included a distinguished panel of speakers including Professor Micheal Cousins, Dr Timothy Deer, Dr Peter Georgius Professor Nicolai Bogduk, Dr James O'Callaghan and Dr Charles Brooker.

The meeting consisted of several presentations relating to current topics within the field. Each of the speakers presented information relating to treatments and new technologies that serve to impact the treatment of patients with neuropathic pain. This type of pain results from inappropriate signals in the nervous system. Unlike physiologic pain, which serves to warn and protect individuals from possible or actual injury, neuropathic pain serves no useful purpose.

First on the program was a presentation by Professor Cousins on ‘Neuropathic pain: current concepts in relation to neuromodulation'. For some, neuropathic pain may be short lasting, while for others it may become persistent and debilitating. Recent evidence has suggested that there may be a small family of genes that determine the likelihood of progression from a short lasting to a persistent neuropathic pain.

The management of neuropathic pain can involve both pharmacologic and non-pharmacologic options. The use of new non-opioid drugs delivered into the spine were discussed including the possibility that these drugs may create a resurgence in the use of spinal drug administration. Non-pharmacological therapies, such as electrical stimulation of nerve fibers (neurostimulation), continue to evolve with greater use and enhanced technology.

Dr Deer discussed neurostimulation and the topic of ‘Advances in Neuromodulation'. With 75,000 neurostimulators implanted worldwide each year, the field of neurostimulation is growing dramatically. Neurostimulators can be used in the treatment of pain, certain neurological diseases including Parkinson's disease and other conditions including angina.

Dr Deer discussed technological advances including lead technology, generator technology, computer technology platforms, selecting the right patient for neurostimulation and continuing physician education in this field. He also discussed areas that have the potential to change the future of the field but as yet have not made a clinical impact such as wireless technology and self contained systems.

The discussion included a review of recently researched drugs including octreatide, which has been shown to have some efficacy in neuropathic pain; and gabapentin, an antiepileptic drug currently being studied in scientific trials for its use in pain management. Several medications derived from the venom of the marine cone snail, conotoxins, where discussed. Ziconotide (Prialt) was included, which is a non-addictive analgesic 1000 times more potent than morphine.

Dr Georgius presented ‘Non-nociceptive effects of intrathecal agents'. This presentation addressed some the effects of drugs administered into the spinal canal (intrathecal). While these agents have a significant role in pain management, they can also influence other systems in the body including endocrine (hormone) and immune systems which can effect pain modulation.

A major hurdle in assessing the effectiveness of a medication or procedure is whether or not the response reported by a given patient is attributable to the active component of the intervention. Professor Bogduk explained the use of ‘N of 1 trials & application to neuromodulation' in answering this question. N of 1 trials are a method of assessing the likelihood that the responses reported by the patient are actually a direct result of the medication or procedure used.

In this type of trial there is only one participant, the patient. They are randomly allocated to receive either active treatment or treatment with no active component (placebo or sham). The placebo treatment involves the same methods as active treatment with the exception that there is no active component. For example, if the treatment was a medication, active treatment would involve swallowing a capsule containing the drug. This is compared to the placebo treatment which would also involve swallowing of the capsule but without any drug inside. In this way patients are ‘blinded' in that they are not aware of whether or not they are receiving the active or sham treatment. This is referred to as a single blind study. The doctors or staff treating the patient may also be blinded, referred to as a double blind study. The purpose of this is to avoid bias which may alter the results.

If the response of the patient is attributable to the intervention, the patient will consistently respond to treatment with the active intervention but not to the sham intervention. To overcome chance variations, multiple repetitions are required. The number of repetitions is dependant on the magnitude of the response and the differences in the scale of response to active or sham treatment. The larger the differences, the most statistically significant the results are, so the fewer the number of repetitions that will be required.

Persistent or recurrent pain, reduced functionality and reduced quality of life despite successful surgery characterises patients with failed back surgery syndrome. It has been shown in selected patients that pain reduction, improved quality of life, reduced use of analgesics, improved sleep and functionality including work can be achieved with spinal cord stimulation.

Dr O'Callaghan presented the PROCESS results; a study of 100 patients randomised to either conventional medical management (CMM) alone or CMM plus spinal cord stimulation. The conclusions were that spinal cord stimulation can result in sustained pain relief (24 months) as well as improved functionality, health related quality of life and patient satisfaction.

Dr Brooker summarised the use of pumps to deliver medication into the spinal canal and the current evidence for the use of different drugs in patients with spinal cord injury and multiple sclerosis. In Dr Brooker's presentation on ‘intrathecal drug delivery for spinal cord injury: current status and future direction', he also discussed technical issues that relate to the use of implantable pumps in these patients.

To conclude the presentations, Dr Deer presented ‘Peripheral nerve stimulation (PNS) and peripheral nerve field stimulation (PNFS)'. These techniques are based around the principle that nerve stimulation can effect the transmission of pain signals. By interrupting the transmission of pain signals, peripheral nerve stimulation has the ability to relieve the pain experienced by patients. Complications of both PNS and PNFS techniques include cellulitis and peripheral nerve injury as well as mechanical dysfunction of the leads and/or generator. The presentation focused on methods to achieve optimal outcomes in terms of increased pain relief and decreased complications.

References

International Neuromodulation Society. Neuromodulation: New Frontiers. 4^th Scientific Meeting, The Australian Chapter, International Neuromodulation Society.