Sunday, July 1, 2007

Recent paper on rTMS and pain

The Journal of Pain just published a review article on the effects of rTMS on experimentally induced and chronic neuropathic pain. They looked at a seven studies that used rTMS to modulate experimentally induced acute pain brought on by ischemic muscle pain, cold immersion, capsaicin or laser stimulation. Those last tow really get to me, I am still recovering from a traumatic expericence as a child at a Mexican restaurant in California. I must have been about four and I grabbed a chip-full of homemade salsa that must have been served to the devil himself it was so hot. All I remember after being stunned by the growing four alarm fire in my mouth was the busboy grabbing a glass of milk and pouring it down my gullet. And anything involving lasers requires the obligatory reference to Dr. Evil's "sharks with lasers.."
It seems the findings in the acute pain papers were mixed. The authors conclude that "The varied effects of rTMS on acute pain may have been influenced by the type of experimentally induced pain, the stimulation frequencies used, and the cortical sites of rTMS stimulation." They noted some of the findings from this group of papers included that ability of single session rTMS to alter pain thresholds.
There were 16 chronic neuropathic pain papers that were included in this group that included approximately 250 patients with a wide variety of conditions including thalamic stroke, trigeminal neuralgia, CRPS, peripheral neuropathy, spinal cord injury, brahcial plexus injury, back pain, thalamotomy pain and osteomyelitis. The papers included used varying protocols including single session and multiple sessions.
In eight of the studies there was a "significant decrease in post-TMS VAS (visual analog scale, usually a 0-10 scale of pain) means as compared with pretreatment means...". To confuse issues there were some studies that reported a decreased in studies that used sham TMS to control for the placebo effect. However, the post-TMS VAS scores were significantly lower than the sham scores.
Some of the numbers that the authors present caught my eye: 62% of patients acheived at least 30% reduction in pain based on their VAS scores after TMS and almost 30% of those patients had at least a 50% drop in their pain score.
They then go on to make some generalizations about TMS protocols including the type of coil used, fast vs slow, the number of pulses used and the location of stimulation. None of the studies reported any adverse affects.
Once again, this presents some thought provoking information and causes me to continue to consider therapeutic neuromodulation with TMS may be in our future.
At what point does someone take the plunge and start offering this to patients with refractory neuropathic pain. I have seen these patients and they are miserable. Their pain is their life, and if you could offer someone a 30-50% reduction in their pain, even if it involved ongoing treatment, I have to wonder if this would be potentially life-altering. Just a thought....