Slurpees, margaritas, ice cream - they can hurt so good.
No-one really knows why, but scientists think that stabbed-in-the-forehead feeling (sphenopalatine ganglioneuralgia) occurs when the temperature of your palate doesn't have time to normalise between spoonfuls of flavoured ice.
The capillaries in the roof of your mouth dilate rapidly, filling with warmth-inducing blood, and that sudden expansion could trigger nerves at the back of your palate (the sphenopalatine ganglion) to fire off urgent messages to your brain: "OMG, the head is freezing!"
In response, blood vessels in your head swell in a pattern that resembles a migraine - although brain freeze lasts less than a minute.
To cure a cranium chill, press your tongue hard against the palate to thaw it quickly, or breathe into your hands to heat your mouth.