We all know what it feels like to get a headache - it could be a dull throb or an acute pain, like someone taking a hammer to the inside of your skull. Despite the frequency with which many people experience headaches, we still have very little understanding of how or why they occur, or how to prevent them.
Headaches are commonly associated with the expansion of blood vessels in the brain, known as vasodilation, which allows for increased cranial blood flow. More blood flow then leads to a build-up of local pressure and a sensation of pain. There are differing theories on the cause of this increased blood flow, such as increased brain activity or nerve stimulation. The methods available for studying headaches, however, do not allow researchers to differentiate between the various causes of increased blood flow. It is impractical for patients to sit around in the laboratory waiting for the onset of a headache, so researchers must rely on data gathered from patients who have already developed headaches or on headaches induced by medications, which may be different than those that occur spontaneously.
Recently, though, Dr. Jorge Serrador and a team of researchers from Veterans Affairs and Harvard Medical School have turned to "brain freeze" - that acute, painful sensation that we get from eating ice cream too quickly - to better understand the mechanisms by which headaches occur. "We realized that brain freeze was a type of headache we could induce without medications," explained Dr. Serrador. To recreate the sensation of brain freeze in the laboratory, Dr. Serrador and his team had volunteers drink ice water. They didn't want to use something sweet, like ice cream, because the burst of sugar could complicate their observations.
The study included 27 healthy volunteers who quickly drank ice water from a straw until they started to get the headache associated with brain freeze. When this happened, the volunteers would raise their hand to indicate the onset of the headache, and stop drinking the ice water. Their hand remained raised until the pain subsided, when they would lower their hand. The volunteers used visual rather than verbal cues to avoid complications when measuring blood flow.
While this experiment was going on, Dr. Serrador and his team measured how fast blood was moving through the blood vessels in the cerebrum, the largest part of the brain. To do this, the researchers used a completely noninvasive technique known as transcranial doppler.
Here's how transcranial doppler works: we are all familiar with the Doppler Effect - the train whistle that changes pitch as the train approaches and then gets further away again. Using this same principle, the researchers directed very high frequency sound waves into the brains of volunteers. The sound waves bounce off the red blood cells at a certain frequency and indicate how fast the blood cells are traveling. One advantage of this method is that it allows the researchers to collect data millisecond by millisecond. This is very important when talking about the onset of a headache, which may occur in only several seconds.
Using transcranial doppler, Dr. Serrador and his team measured blood flow, known as Cerebral Blood Flow Velocity, in both the middle and anterior cerebral arteries . The anterior cerebral artery provides blood to the very front part of the brain; the middle cerebral artery feeds most of the rest of the cerebrum. The researchers found a large increase in blood flow in the brain, with the increase most pronounced in the anterior artery.
"It appears that the frontal lobes have the biggest increase in blood flow just before the headache develops," explained Dr. Serrador.
Blood flow remained constant for the duration of the headache and then decreased back to normal as the pain subsided.
To control for any effects the water itself might have on brain blood flow, Dr. Serrador performed the same experiment with the same volunteers using water at room temperature. As expected, the volunteers did not develop headaches. "These findings are further evidence that an increase in blood flow is a critical component of headache development," Dr. Serrador commented.
In follow-up experiments, Dr. Serrador and his team are planning to block the increase in brain blood flow associated with brain freeze to see if this could prevent the headache from occurring. The researchers will also work with veterans who experience post-traumatic headaches to see if they show a similar response compared to healthy volunteers. "If the veterans have a different response, that would tell us that perhaps we're looking at this in the wrong way," commented Dr. Serrador. On the other hand, if they showed a similar or exaggerated response, this would allow the researchers to think about potential targets for treatment. Dr. Serrador is hopeful that this research will lead to treatments for frequent headaches that are caused by an increase in brain blood flow.
Dr. Jorge Serrador is Associate Professor of Physiology & Pharmacology at New Jersey Medical School, Instructor in Neurology, Harvard Medical School and Associate Director of Research at the War Related Illness & Injury Study Center, Dept of Veteran Affairs. His research focuses on the regulation of blood flow in the brain. When not in the laboratory, Dr. Serrador enjoys traveling and spending time with his family.
For More Information:
- Blatt MM, Falvo M, Jasien J, Deegan B, Laighin GO, Serrador J. Cerebral vascular blood flow changes during "brain freeze'. The FASEB Journal. 2012;26:685.4.
To Learn More:
- National Headache Foundation. http://www.headaches.org/
- American Headache Society Committee on Headache Education. http://www.achenet.org/
- Johns Hopkins Headache Center. http://www.hopkinsmedicine.org/neurology_neurosurgery/specialty_areas/headache/
Written by Rebecca Kranz with Andrea Gwosdow, PhD at www.gwosdow.com
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