You know the sensation. You eat or drink something too cold, too fast, and your head explodes in excruciating, but short-lived, pain. It's caused by stimulation to the sphenopalatine nerve (see picture), which emerges from your brain and then splits into a multitude of branches that sit right above the roof of your mouth and just below the surface of your cheeks and upper lip.When the sphenopalatine nerve is stimulated by cold, it initially causes surrounding blood vessels to constrict in response. But very soon thereafter, for reasons not entirely understood, the brain reacts—over-reacts, really—to this vasoconstriction by radically dilating the blood vessels to rewarm them. This sudden pulse of blood causes the sphenopalatine nerve to register pain, which is usually manifested elsewhere in the head. (In my case, the dead center of my forehead lights up in discomfort, though it can occur in the temples or sides of the head as well.)
Most people experience brain freeze because something cold hits the roof of the mouth. In my case, I experienced it because ice-cold water hit my face when I went underwater. For a long time, I would desperately pull my neoprene hood down toward my eyes, trying to cover up the painful spot in my forehead. But now I realize that it's being caused by the nerves in my face.
I've pondered various ways to prevent this, including somehow incorporating a neoprene facemask into my winter surf gear. But so far the only solution I've come up with is to keep my face out of the water as much as possible—which means chasing smaller surf during the coldest days of winter.
If you have suggestions for some other way to prevent cold-water brain freeze, I would love to hear them!
“Equipped” is an AMC Outdoors blog, written by Matt Heid.