Transcranial Magnetic Stimulation
In transcranial magnetic stimulation (TMS) a rapidly changing magnetic field is applied to the surface of the scalp either as a single pulse or as trains of repeated pulses. Since single-pulse TMS can disrupt cortical spreading depression in animals it was reasoned that it might be therapeutic in migraine, and several studies have been conducted.[66–71] Clarke et al. compared the effect of two single pulses of high- and low-intensity TMS in migraine patients both with and without aura. All the migraine with aura patients reported that TMS had an immediate effect on their headache, and 32% of all patients had no headache recurrence 24 h after stimulation.
In 2010, Lipton et al. published results of a randomized sham-controlled study on 164 migraine with aura patients. They used a portable TMS device, delivering two single pulses at 30-s intervals, to stimulate the occiput within an hour of aura onset. A total of 39% of TMS and 22% of sham-stimulated patients were pain free at 2 hours. The difference was significant, and sustained pain-free rates at 24 h and 48 h were also significantly better in the TMS group. However the global assessment of relief was better in the sham arm than the TMS arm; and nausea, photophobia, phonophobia and use of acute medication did not differ between groups. In view of the small difference in efficacy between real and sham stimulation, the utility of TMS in acute migraine with aura cannot be considered established.
Since a functional magnetic imaging study had shown that the left dorsolateral prefrontal cortex exerts an inhibitory control on pain pathways in humans, Brighina et al. investigated high-frequency (20 Hz) repetitive TMS to this area in a randomized study on 11 chronic migraine sufferers, with six receiving TMS and five receiving sham stimulation. While control patients experienced no changes in outcome measures, those who received TMS had significant reductions in attack frequency, headache index and number of abortive pills used in the month after treatment compared with the month before treatment; the effects lasted for up to 2 months. However, in another study on 13 patients with chronic migraine, repetitive TMS (10 Hz), also applied to the dorsolateral prefrontal cortex, proved less effective than sham stimulation after 2 months.
Teepker et al. applied 1 Hz repetitive TMS (two trains of 500 pulses at the motor threshold on 5 consecutive days) over the vertex in 27 patients with episodic migraine with or without aura, based on the rationale that low-frequency repetitive TMS may return a hypothesized hyperexcitable migrainous brain to normal. The number of attacks and days with attacks did not differ significantly between the TMS group and sham stimulation group. Further studies are required to determine whether or not TMS is effective in migraine.
Future Neurology. 2013;8(4):457-467. © 2013 Future Medicine Ltd.