During the “dawg days” of summer in Athens, GA nothing is better than cooling down with any number of favorite summer treats like ice cream, popsicles, or an ice cold beer. Unfortunately as anyone that has ever eaten ice cream knows (roughly 100% of the population, by my estimate) the euphoria that accompanies a frozen treat can quickly turn into a blinding headache.
It’s common experience that if you drink cold things fast, a headache will quickly follow. It’s practically a rite of passage akin to learning not to touch a hot stove by burning your hand. However, until recently the underlying cause of brain freeze has escaped the understanding of scientists.
What specifically about cold liquid makes it feel like your neurons are taking off the gloves to throw down in a cerebral hockey match? Surprisingly, brain freeze is not ice cream induced hypothermia as the name would suggest. The brain is incapable of feeling pain because it lacks the equipment to do so. Nocireceptors, the sensory nerve fibers that alert you when the stove is hot, are not present in gray matter. Instead of being concentrated in the brain the headache actually starts with the mouth.
Next time you accidentally drink a milkshake too fast pay attention to where the pain is concentrated. You should notice a throbbing pressure behind the eyes, forehead, and sometimes the back of the neck, the symptoms of a vascular headache (caused by increased blood pressure). This is a result of rapid vasodilation and vasoconstriction, the widening and tightening of blood vessels, of two of the brain’s major arteries, the internal carotid artery and the anterior cerebellum. The juncture of these arteries acts like a sort of thermostat for the brain. With every gulp of cold liquid the arteries at the back of the throat constrict, which increases blood pressure and lowers the temperature of the brain.
Vasodilation counteracts this temperature drop by rapidly expanding the arteries and allowing warm blood to be pumped into the brain. This is the climax of brain freeze, when you’re left trying to decide whether that little taste of heaven was worth the few seconds of feeling like you’ve swallowed a heavy metal concert.
The brain is sensitive to temperature, but a temperature drop is not the reason why you’re head hurts after a smoothie. Pressure causes the headache, not temperature.The warm blood pumping through dilated arteries puts pressure on the meninges, the membrane separating the brain from the skull. This triggers pain at the base of the brain where the two arteries and meninges meet. The trigeminal nerve, which is responsible for all facial sensation, then transmits the pain signal to the forehead and face.
Thankfully this all happens extremely fast and the headache usually passes in a matter of seconds, but if you want immediate relief drink warm water or press your tongue to the roof of your mouth to warm your brain up even faster.
In a nutshell it is not the brain freezing that hurts, it’s when it warms back up.
More specifically it’s the rise in pressure caused by the rush of warm blood that causes pain. This leads some scientists to believe brain freeze or rapid vasodilation is a defense mechanism and a way to regulate the brain’s temperature. Although the reasons are not clear, migraine prone brains are more likely to trip this temperature resistant mechanism.
Brain freeze is basically the brain’s only defense against ice cream, but it is also a useful proxy for the study of migraines and even severe brain trauma. Its utility stems from the fact that a brain freeze is a vascular headache and is easily induced in a lab setting. This is valuable because migraines are unpredictable by nature, whereas scientists can induce a brain freeze by “treating” patients to a big bowl of ice cream. Studying brain freeze most likely will not lead to a better understanding of the underlying cause of migraines, but it could lead to drugs that prevent vasodilation and thus alleviate symptoms.
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