The use of slow-frequency prefrontal repetitive transcranial magnetic stimulation in refractory neuropathic pain

A number of antidepressant medications, as well as electroconvulsive therapy, have been shown to reduce chronic pain. Slow-frequency repetitive transcranial magnetic stimulation (rTMS) applied to the right dorsolateral prefrontal cortex has also been shown to have an antidepressant effect. Given the high degree of suffering experienced by subjects with chronic neuropathic pain and the treatment resistance noted in this population, the use of slow-frequency rTMS as adjuvant therapy may be of significant clinical benefit.

Fifteen sessions of 1-Hz rTMS (1600 stimulations/session) were applied to the right dorsolateral prefrontal cortex as adjuvant treatment in 9 subjects with refractory neuropathic pain over 3 weeks. Pain and depression ratings were performed at baseline, weekly during rTMS treatment, and monthly for up to 3 months after treatment.

Five males and 4 females participated, and all had longstanding refractory neuropathic pain (range, 1-19 years), with an average baseline pain rating of 7.3 and no depression (Hamilton Rating Scale for Depression average, 3.6; range, 0-8). Three subjects had a greater than 50% decline in pain ratings by the completion of rTMS treatments, and 1 subject responded more slowly with greater than 50% improvement in pain by the end of the 3-month follow-up. An improvement in pain ratings was noted in responders within the first week.

Although these are preliminary findings in an open treatment trial, the subjects in this trial are among the least likely to have a placebo response. Given that rTMS is a well-tolerated and noninvasive intervention, any sustained improvement in neuropathic pain with rTMS is encouraging.