The dark suffering of neuropathic pain
September 30, 2002
Dr Gary Bennett investigates its mysteries
Imagine a pain so excruciating that words fail to describe it and doctors can't explain it. A pain that may in fact worsen over time. Tragically, some people don't have to imagine such pain, they experience it and it makes their life unbearable. Neuropathic pain, as it is called, has long been the focus of investigation by Dr Gary Bennett, professor in the department of Anesthesia, cross-appointed to the Faculty of Dentistry, and director of research at the McGill University Pain Centre located in the Montreal General Hospital of the MUHC (McGill University Health Centre).
Basically, neuropathic pain can be described as a malfunction in the nervous system that usually follows injury to the nerve or to certain regions of the spinal cord or brain. Dr Bennett examines possible causes for this kind of pain and searches for drugs that may be used to treat the condition. One compelling example of neuropathic pain is 'Phantom Limb Syndrome,' a condition in which a patient feels pain in a limb that is no longer there. Diabetics, people with nerve damage due to shingles (an adult form of chicken pox), and even patients on certain drug treatments may also suffer from various forms of neuropathic pain.
The excruciating pain can often become chronic, and unresponsive to most painkillers. It seems that the longer a patient waits to seek treatment, the harder the pain may be to control. "Neuropathic pain is unlike ordinary pain -- it does not respond to the aspirin-like drugs, and it responds very poorly or not at all to even strong opiates like morphine," says Dr Bennett who is working with the pharmaceutical industry to find new and effective drugs. In terms of options, researchers have had some success with anti-epileptic drugs such as Neurontin (Gabapentin). There has also been some preliminary evidence suggesting that the immune system may play an important role in these conditions. "We know that chronic, unrelieved pain suppresses the immune system," says Dr Bennett. For this reason drugs that modulate the immune system may turn out to be a useful mode of therapy.
Dr Bennett is also collaborating with Dr Mark Ware of the department of Anesthesia and the Pain Centre in studying the effects of smoked cannabis on neuropathic and other forms of chronic pain. A wealth of anecdotal evidence suggests that cannabis may help control pain where opiates and other drugs fail, but Drs Ware and Bennett are the first researchers to study these claims through controlled clinical trials.
"The study of neuropathic pain is now one of the leading areas of research in all of neuroscience," says Dr Bennett. "We have discovered that the mechanisms that lead to neuropathic pain at least partly resemble those that are responsible for learning and memory," he notes. "And we also recognize that there's a deep affinity with epilepsy." These common features, according to Dr Bennett, have attracted tremendous research interest to the field of neuropathic pain.
The expanding research is most welcome. "This type of pain is day-in and day-out, for months, or even years," say Dr Bennett. "It's torture. And in many cases we just can't do enough to make that pain go away." He stresses the need for a deeper understanding of the neuropathic condition: "the more we understand it at a basic level, the more intelligently we can search for or design new drugs to help control it, or find other kinds of therapies to help make the pain go away." Dr Bennett's research may eventually unravel the mysteries of neuropathic pain and relieve the dark suffering associated with it.
This is the sixth in a series of interviews with McGill pain researchers whose investigations are funded by the Canadian Institutes of Health Research. The project, carried out in cooperation with The McGill Office for Chemistry and Society, aims to highlight recent advances in the study of pain. Permission is granted to reprint in whole or in part.
