Reader Susann writes in to ask, "What exactly is the cause of a brain freeze?"

You may know brain freeze by one of its other names: an ice cream headache, a cold-stimulus headache or sphenopalatine ganglioneuralgia ("nerve pain of the sphenopalatine ganglion"), but no matter what you call it, it hurts like hell.

Brain freeze is brought on by the speedy consumption of cold beverages or food. According to Dr. Joseph Hulihan, a former assistant professor in the Department of Neurology at the Temple University Health Sciences Center, ice cream is a very common cause of head pain, with about one third of a randomly selected population succumbing to ice cream headaches.

So what causes that pain?

As far back as the late 1960s, researchers pinned the blame on the same vascular mechanisms—rapid constriction and dilation of blood vessels—that were responsible for the aura and pulsatile pain phases of migraine headaches.

When something cold like ice cream touches the roof of your mouth, there is a rapid cooling of the blood vessels there, causing them to constrict. When the blood vessels warm up again, they experience rebound dilation. The dilation is sensed by pain receptors and pain signals are sent to the brain via the trigeminal nerve. This nerve (also called the fifth cranial nerve, the fifth nerve, or just V) is responsible for sensation in the face, so when the pain signals are received, the brain often interprets them as coming from the forehead and we perceive a headache.

With brain freeze, we're perceiving pain in an area of the body that's at a distance from the site of the actual injury or reception of painful stimulus. This is a quirk of the body called "referred pain," and it's the reason people often feel pain in their neck, shoulders and/or back instead of their chest during a heart attack.

To prevent brain freeze, try the following:

• Slow down. Eating or drinking cold food slowly allows one's mouth to get used to the temperature.

• Hold cold food or drink in the front part of your mouth and allow it to warm up before swallowing.

• Head north. Brain freeze requires a warm ambient temperature to occur, so its almost impossible for it to happen if you're already cold.

Now, back to Susann. Maybe you flossers can help her out. When she eats ice cream, it's not her brain that freezes, but her back. "I get a back freeze," she says. "What's up with that?" My guess would be it's a neurological quirk that has the brain interpreting the cold stimulus and pain signals as coming from her back. But I'm not a doctor, I just play one on the web. Anyone with a little more authority have a better idea?

[Image courtesy of Donuts4Dinner]