Thursday, October 4, 2007

Migraines Zapped with tDCS

The same group ( I trained with them learning the technical aspects of tDCS and TMS) at Harvard that I have written about in the past just had an article published about one of their trials in IEEE Spectrum Online .

The gist of the article is that by using tDCS (low voltage electricity that runs through the brain via a couple of electrodes at very specific locations on the skull) migraineurs were getting some serious relief. The study is currently ongoing so the results have yet to be seen.
"The investigators, Dr. Felipe Fregni and Soroush Zaghi, both of Harvard Medical School, have recruited 24 patients who suffer migraine headaches at least 15 times per month. At scheduled intervals, which may or may not coincide with migraines, Fregni attaches electrodes to a subject’s scalp and passes 2 milliamps of current through the brain, targeting the locus of pain. Two months into the study, he is encouraged by what he is seeing. “In the initial sample, the results went in the direction we predicted,” he says. One of the main themes that I walked away from my week at Harvard with was that the brain is a HUGE BLACK BOX!!!! The breadth and depth of our understanding of how and why the brain works the way it does is superficial at best. As a result of the basic science that is going on with all of the new tools available to researchers, including TMS and fMRI, we are starting to crack open the box. But every little tidbit we figure out just makes me realize that the volume of the box is staggering."

A colleague asked me recently what the proposed mechanism of action was for tDCS and TMS. My short answer was "I don't really know". The long answer has to do with re-balancing the excitatory and inhibitory inputs of certain areas of the brain that affect areas "down stream" from the area of action.

"Following that theory, what triggers migraines is just an extreme example of what causes ordinary headaches in the normal brain. “If you stay up all night, three days in a row, and there are loud sounds and bright lights, you’re going to get a headache, too,” Fregni says. For people with migraines it just takes much less stress because the baseline of activity in certain areas of the brain is much higher, he says.
 Neurons, the cells that carry messages throughout the brain, are constantly receiving electrical inputs from surrounding cells. They integrate the voltage signals, and if the total is strong enough the neuron fires—sending a pulse of voltage out to other neurons to which it’s connected.
 During tDCS, the current hyperpolarizes the afflicted area of the brain, making the neurons less likely to fire. In the short term, the treatment usually staves off an encroaching attack, but tDCS could have long-term benefits as well. Many studies have determined that when repeatedly exposed to a hyperpolarizing current, neurons eventually become less excitable, a process called long-term depression. The stimulation would take advantage of that phenomenon to prime the migraine-prone regions of the brain so that one great flash of light would not be enough to overload the whole system."