A primer on Neuropathic Pain

Editor’s Note: Dr Mailis-Gagnon will be writing for CARP Action Online on a semi-regular basis. Should you have any questions about pain please write to us at [email protected]. We will try to integrate some of your concerns in Dr. Mailis- Gagnon’s future columns.

If you twist your foot by accident, you will get what we call a simple “sprain”, with swelling of the ankle, some bruising and some deep aching pain for a few days. If you break a bone, you will experience aching, throbbing pain that settles quickly once the arm or the leg is in a cast. If you have arthritis in your joints you know that the pain comes with activity and will respond well to aspirin-like drugs. Food poisoning will give you twisting cramping pain from inflamed guts. All these pains are known to scientists under the umbrella name of “nociceptive pain” and we are all too familiar with them. These are the pains that come from broken bones, pulled muscles, inflammation and even pain from your heart, your gallbladder or the gut.

But there is another kind of pain, a strange one that comes from cut or pinched nerves (like the sciatic nerve at the back of your legs), an injured spinal cord (as in the case of spinal cord injury with paralysis) or a damaged brain (after a stroke or a trauma to the head). This type of pain is called “neuropathic” pain and it’s kind of a “short circuit” in the body’s sensory apparatus. Neuropathic pain may make you feel that an injured body part is on fire, that “ants are crawling under your skin”, that a knife is getting into your flesh and cuts you suddenly, or that you are hit by a lightning bolt or shot with a shotgun. A draft of air can bring a spell of sharp shooting pains, the touch of the clothes becomes intolerant, the warm water of the shower is scorching, or hundreds of pins and needles are pricking your skin. If you feel this kind of pain, you are not alone. About 8% of Canadians suffer from neuropathic pain, which means that 2.5 million in our country (one million in Ontario alone) are victims of this pain, a pain that has “many causes”, but only one face, “the face of distress and suffering”.

Some conditions are extremely prone to causing neuropathic pain. For example, 75% of people over 75 years of age will continue to experience post-herpetic neuralgia after an attack of shingles; 65% of patients with Multiple Sclerosis, 70% of people with spinal cord injury, 75% of people with amputation and 54% of patients with AIDS will also experience neuropathic pain. What about 20-30% of patients with diabetes and painful diabetic neuropathy, 8% of people after a stroke, 14-15% of patients with mastectomy for cancer, thoracotomy, heart bypass surgery and numerous other operations, who continue to experience relentlessly neuropathic pain? The list is not done: patients with afflictions of the spine like a chronically herniated disc or pinched spinal nerve, those with nerve injuries after accidents or those who received chemotherapy for cancer can suffer as well from lifelong neuropathic pain.