I opened a recent issue of Arthritis and Rheumatism (the official journal of the American College of Rheumatology), and read an interesting study on the effect of transcranial direct current stimulation on pain and quality of life in fibromyalgia patients. It was interesting because it is one more piece of research focusing on modulating how our brains process pain, thereby hopefully reducing perceived pain.

In this study, female patients with fibromyalgia were randomly placed into three different treatment groups: two treatment groups underwent stimulation of different parts of the brain for five days, and the third group underwent a "fake" stimulation. The researchers noted a large decrease in pain in the patients undergoing stimulation of the primary motor cortex, and this lasted about three weeks. The same investigators performed a different study on patients with spinal cord injury, and found that transcranial direct current stimulation improved the pain these patients chronically experience. A more widely studied (but similar) treatment modality, known as transcranial magnetic stimulation, also stimulates the nervous system noninvasively and has been found to have pain-relieving properties in both healthy individuals and patients with chronic pain.

It may be that such stimulation is triggering inhibitory mechanisms, and thus dampening the volume of the pain input that travels to the brain. Or perhaps this cranial stimulation is reducing the absolute amount of pain input. The guessing game on why aside, it is interesting to note that researchers are continuing to focus on how pain is reduced at the level of the brain. Generally, we think of reducing pain by attacking the source, so to speak: for example, we inject with cortisone a painful shoulder bursitis, or we replace a painfully arthritic hip. But pain can often persist to some degree once these painful complaints are treated; perhaps the pain can be made less by attacking the central processing area, the brain.

Chronic pain can result from disturbances in the processing that goes on in the brain, often in the setting of no obvious physical abnormalities on biopsy or lab testing (as in fibromyalgia or irritable bowel syndrome). In a chronic pain syndrome such as fibromyalgia, there is evidence of so-called pain amplification, as patients may feel intense pain with just the slightest touch. There may be an increase in experienced pain on the part of chronic pain patients because there is some defect at the level of, for example, the nerves which supply muscles (although this has certainly not been clearly proven), and/or there may be a problem at the level of the spinal cord or brain---a more central problem.

It may be that chronic pain responds fairly well to anti-depressants (which increase inhibitory activity to lessen pain impulses) and anti-seizure medications such as Lyrica or Neurontin (which decrease excitatory activity to lessen the progress of pain impulses) because there is such a large component of pain which is due to defective central control of the pain experience in the brain. Unfortunately, some of the more severe chronic pain patients eventually end up on multiple medications, with many of their associated side effects. The use of modalities such as direct current stimulation could be an interesting addition to the treatment choices for the chronic pain patient, combined with biofeedback, psychological counseling, and, perhaps, fewer medications.