As we close our series on pain, let’s recap what we’ve covered. Our focus has mainly been on the chronic variety, which may never go away and which permanently disables large numbers of people in our society and around the world. Acute pain, on the other hand, is its opposite, and usually is the result of a disease or injury that goes away as we heal.
We began this series with the two most common ailments: back pain and headaches. We then covered some of the more unusual, but well-known chronic pain syndromes, namely Trigeminal Neuralgia, Fibromyalgia and Complex Regional Pain Syndromes. One theme that has emerged is that chronic pain syndromes are difficult to treat.
I have reserved this last installment to talk about some of the more technical methods used to treat chronic pain syndromes; some have been around for a while, and others have arisen from recent technological advances.
As before, there are many new terms to understand. One is nociceptive pain, which refers to abnormally persistent stimulation of otherwise normal sensory receptors in our body.
We have many types of sensory cells, each of which responds to a different type of stimulus. For example, there are receptors for heat, touch and even the position of our joints. It is believed that these receptors can begin to transmit pain sensation when they are not supposed to, particularly in cancer patients.
Over the years, atypical pain has prompted physicians to look for other ways to manage it. These modalities have ranged from electrical stimulation of the brain to actual destruction of carefully selected areas of the spinal cord and brain. While the former is relatively low risk, the latter requires precise understanding of how to avoid causing more harm than good.
Stimulation of the spinal cord is the most common technique used to address the most difficult chronic pain cases. It has limitations, not the least of which is a poor understanding of how and when it works (which is not often). The up side is that it is not particularly risky. It requires thin electrodes—wires that carry electrical current—to be inserted in the low part of the back, inside the bones of the spine, but outside of the spinal cord. Wires then pass from the electrodes, under the skin, to a programmable battery pack about the size of a hockey puck, which is implanted under the skin of the abdomen. The cool thing is that the battery back is a little computer that can be programmed without opening the skin. A device is simple held over the area where the pack is implanted and digital input can adjust the settings topically. (Any Trekkies in the group?….remember the Tricorder?…Hmmmmm?)
Before I get to more recent approaches of stimulating the brain to control pain, let’s talk about techniques that have been in use for many years that involve destroying carefully selected parts of the brain and spinal cord. Most of these have been abandoned because they are not very effective and they have obvious potential for unsavory side-effects. For example, weakness in the arms and legs and loss of sensation are often involved.
These procedures have often been used for pain related to cancer, and since that disease has traditionally been fatal in a relatively short period of time, the benefits generally outweigh the side effects. In more recent years however, cancers have been better controlled, patients live longer, and therefore limited effectiveness, coupled with troublesome side effects make these treatments less popular.
On the other hand, destruction of small, carefully selected areas of the brain are pretty effective in controlling the abnormal movements associated with Parkinson’s disease, for example. Micheal J. Fox has had one of these procedures. A similar technique has been used with some success in the treatment of severe chronic pain associated with cancers that are unresponsive to all other types of treatment. However, the technique was never approved by the Food and Drug Administration, and all of the experimental investigations have been cancelled.
Small stimulators placed in precisely determined areas deep in the brain are now being used to mitigate the effects of Parkinson’s disease. These have also been tried with limited success in the treatment of chronic pain.
Phantom limb pain, an enigma in the world of human physiology, is one of the types of chronic pain for which deep brain stimulation has had shown success. Those who experience this phenomenon report excruciating and uncontrollable pain in a limb that has been amputated; yes, that’s right, in a limb that is no longer there. The situation has most commonly occurred over the years in soldiers with war injuries. But other types of accidents and diseases can lead to amputations as well. Fortunately, only a small percentage of amputees experience phantom limb pain.
The latest treatment innovation is stimulation of the surface of the brain. Oddly enough, if electrodes can be placed just right on the surface of the brain, yet under the skull, so that muscle twitching can be induced in the area of the pain, it may be relieved.
Well, by now you have probably realized that human physical pain, especially chronic pain, is a complex topic to which volumes have been devoted. While justice cannot be done to this topic in a series of six essays, we hope you have gotten a sense of the breadth and depth the subject, and perhaps new ideas to treat your own pain or that of friends and family.
by Thomas Chappell, MD