Scientists think they know why eating something frozen such as an ice lolly or ice cream can cause a sudden excruciating headache, often called brain freeze.
That ice cream headache, or sphenopalatine ganglioneuralgia as it is known to scientists, is caused by changes in the blood flow in the brain when chilled foods quickly come into contact with the mouth's upper palate, according to a new study.
Previous research has found that migraine sufferers are more prone to brain freeze than others who don't get migraines, suggesting that the two types of headache might have some type of common mechanism. Studying how brain freeze occurs may give new insights into the mechanisms behind other types of headaches such as migraines, and could lead to new treatments for them, the researchers said.
In the study, scientists from the National University in Galway and Harvard Medical School deliberately induced brain freeze in 13 healthy volunteers by asking them to sip ice water through a straw pressed against their upper palate. The experiment was also repeated using water at room temperature.
As the volunteers did this, the researchers monitored the blood flow in the brain arteries using transcranial Doppler - a type of ultrasound.
The volunteers were asked to raise their hand when they experience the pain of brain freeze, and to do so again when the pain receded.
The ultrasound revealed that one artery in particular, called the anterior cerebral artery, dilated rapidly and flooded the brain with blood when the volunteers felt pain. Soon after the dilation occurred, the same blood vessel constricted as the volunteers pain receded.
The researchers said that the dilation and constriction of the cerebral artery may be a type of self-defence mechanism for the brain in response to severe cold.
"The brain is one of the relatively important organs in the body, and it needs to be working all the time," said study co-author Jorge Serrador of Harvard Medical School.
"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, the sudden influx of blood could raise pressure and induce pain. And when the blood vessels start constricting again, it may be a way to bring pressure down in the brain before it reaches dangerous levels, Dr Serrador said.
He added that similar alterations in blood flow could be at work in migraines, post traumatic headaches, and other headache types.
If further studies confirm the research, then drugs that block the sudden dilation of these blood vessels or others that prevent them from restricting may help to treat these types of headaches.
The study findings were presented at the meeting Experimental Biology 2012 in San Diego.
