Brain freeze is a universal experience - almost everyone has felt the near-instantaneous headache brought on by a bite of ice cream or slurp of ice-cold soda. It occurs when something extremely cold touches the upper-palate (roof of the mouth) - normally when the weather is very hot, and the individual consumes something cold too fast.
Harvard Medical School scientists say they now have a better idea of what causes brain freeze. Since migraine sufferers are more likely to experience brain freeze than those who don't, it may share a common mechanism with other types of headaches caused by local changes in brain blood flow.
According to study leader Dr. Jorge Serrador, a cardiovascular electronics researcher, previous studies assessing physiological changes that might prompt headaches have mainly relied on various drugs, or brought in patients already in the throes of a migraine to the lab. However, both methods have their limitations. Pharmacological agents can induce other effects that can make results misleading, and since researchers can't wait for migraine sufferers to experience a migraine in the lab, those studies miss the crucial period of headache formation that occurs sometimes hours before scientists were able to study these patients.
To induce headache inside the lab and study it from start to finish, Serrador explains, brain freeze is a perfect fit. It's easy to bring on and resolves quickly without expensive or complicated equipment or drugs.
In this study, Serrador and his colleague recruited 13 healthy adults. The researchers monitored the volunteers' blood flow in several brain arteries using transcranial Doppler while they first sipped ice water with the straw pressed against their upper palate, and then while sipping the same amount of water at room temperature. The volunteers raised their hand once they felt the pain of a brain freeze, then raised it again once the pain dissipated. Findings showed that the anterior cerebral artery in particular, dilated rapidly and flooded the brain with blood in conjunction to when the volunteers felt pain. Soon after this dilation occurred, the same vessel constricted as the volunteers' pain receded.
They found that the sensation of brain freeze appears to be caused by a dramatic and sudden increase in blood flow through the brain's anterior cerebral artery. As soon as the artery constricted, the brain-freeze pain sensation wore off.
Dr. Serrador explained that we already know that migraine sufferers are more likely to suffer brain freeze after drinking or eating very cold foods/drinks, compared to people who never have migraines. He suggests that some of what occurs during brain freeze may be similar to what causes migraines, and possibly other kinds of headaches, including those caused by traumatic brain injuries.
Serrador and his colleagues speculate that the dilation, then quick constriction, may be a type of self-defense for the brain. "The brain is one of the relatively important organs in the body, and it needs to be working all the time," he explains. "It's fairly sensitive to temperature, so vasodilation might be moving warm blood inside tissue to make sure the brain stays warm." But because the skull is a closed structure, Serrador adds, the sudden influx of blood could raise pressure and induce pain. The following vasoconstriction may be a way to bring pressure down in the brain before it reaches dangerous levels.