(SALT LAKE CITY)—Millions of people who experience an aura before a migraine live with little understanding of the flashing lights, tingling arms, incoherent speech or other symptoms that presage an attack. But a new study led by a University of Utah neurologist shows that these pre-migraine symptoms, caused by a wave of brain activity, may change the way the brain responds.
This wave, called a cortical spreading depression (CSD), might also explain how migraines become chronic in millions of people, according to K.C. Brennan, M.D., Assistant Professor of Neurology at the U of U School of Medicine and senior author on the study.
"CSD moves across the brain like a ripple in a pond," Brennan says. It drives nerve cells to fire uncontrollably, and causes large changes in blood flow. For at least an hour afterward, it changes the way the brain reacts to its environment. "It's like turning up the volume in all of the senses."
Brennan and colleagues published their study in The Journal of Neuroscience in November. Their findings have implications not only for understanding migraines but also for developing better drugs to treat them, according to Brennan.
It's estimated that more than 37 million U.S. residents experience migraines, with about12 million suffering daily attacks. More than 7 million migraine sufferers experience an aura before the attack. Migraines can last from a few hours to three days, with a variety of symptoms. Many U.S. soldiers who received traumatic brain injuries in combat suffer from chronic migraine.
Workdays lost to migraines total more than 110 million each year and cost more than $13 billion, according to the Migraine Research Foundation.
Brennan and colleagues conducted their study with mice, allowing them to carefully measure the sensory response of the brain before and after CSD, and thus model the effects of an aura on sensory processing. After the CSD passed, they saw larger and sharper sensory responses, and a decreased ability to adapt to stimuli.
"The CSD wave causes the brain to react differently," says Brennan. "Every sense is heightened, which is remarkably like what patients describe during their migraines."
The changes – or sensory plasticity – identified by Brennan and colleagues can last long after CSD passes. If repeated over time, they might help explain why some migraines become chronic, according to Brennan.
In addition to increasing understanding of the disease, Brennan is hopeful that his lab's research will ultimately lead to new treatments. Currently, few medications are made specifically for migraines, leaving providers to prescribe short-term painkillers that can actually increase the frequency and severity of attacks, according to Brennan.
"Migraine has been neglected over the years," he says. "Thankfully that is changing, and as we learn more about how migraines work, we will get better ending the suffering they cause."
This research was supported by the following National Institutes of Health Grants (NIH):
R01 MH52083; NS059072; NS070084; and the NIH Loan Repayment Program