Scientists have studied blood flow changes to come up with a theory
The phenomena of "brain freeze" (also known as an "ice cream headache") may seem a bit trivial to draw the attention of a multi-national, multi-disciplinary team of medical researchers. But the researchers decided to study brain freeze as a model for understanding all other sorts of headaches. A gateway headache, if you will.
One problem with studying headaches is that - as many migraine sufferers know - you can't easily predict them. This makes it difficult to study them in a laboratory setting. Someone can wait until they have a migraine and then rush to the lab, but this method means that researchers miss out on the crucial early stages when the headache is forming.
You can induce headaches with drugs, of course. But then there's no way to know if (or how) the drugs are interfering with your research.
Enter the dreaded ice cream headache. Easily induced in a laboratory setting, minimally disruptive to the research subjects (compared to, say, a full-blown migraine), and not requiring any drugs that might interfere with testing. 13 subjects were recruited and made to drink ice water through a straw directed at their palate. (The back of the roof of the mouth seems to be a trigger for the brain freeze.)
The subjects raised their hands when they felt the headache (and I imagine they added "Agggh! Guh! Bwahhhhhh! Ugghhhhh!" as well). The researchers then studied the transcranial Doppler, where they discovered something interesting: the headaches coincided with the dilation of one particular artery.
It seems that in response to drinking something very cold, the anterior cerebral artery opens up and floods the brain with blood. The theory is that this is a survival mechanism in response to (say) falling into an icy river. When your mouth floods with very cold water, your body pours blood - and therefore both heat and oxygen - into your skull to help preserve your brain.
On the down side, that big influx of brain severely raises the blood pressure inside the skull. And that crushing squeeze is no doubt what we interpret as an excruciating headache.
The researchers will be formally presenting their paper at a medical conference this week. One hopes they can arrange to rent a Slurpee machine for the occasion, because DAMN.