Brain freeze—sphenopalatine ganglioneuralgia—is a short headache triggered when something very cold rapidly cools the roof of the mouth or back of the throat. Trigeminal pain pathways refer the sensation towards the forehead.
The brain itself is not freezing
The brain tissue is protected inside the skull and is not chilled by one bite of ice cream. Instead, sudden temperature change affects nerves and blood vessels in tissues supplied by branches of the trigeminal nerve.
Because the trigeminal system also carries sensation from the face and forehead, the brain can localise the signal as head pain even though the trigger is in the mouth.
Slow warming ends the signal
Stopping the cold exposure and pressing the tongue against the roof of the mouth may warm the area; the pain usually passes quickly on its own. Eating or drinking cold items more slowly can reduce the chance of triggering it.
Researchers agree on the referred-pain pathway, while the exact contribution of rapid blood-vessel changes is still studied.
Diagram referred pain
- Draw a mouth, trigeminal pathway and forehead.
- Put the cold stimulus in the mouth.
- Use an arrow to show why the sensation may be located elsewhere.