Oh the brain freeze will blind the weary runner

Like a cold chisel to the head, ice cream headaches are an unfortunate side-effect of what is otherwise a pleasant relief and an effective way to improve athletic performance in hot weather, as suggested by recent research.

Let me explain. (And let me also apologise for my attempted pun, which I blame on summer brain deactivation.)

An ice cream headache, also known as brain freeze or cold stimulus headache, or, if you want to get really fancy, sphenopalatine ganglioneuralgia, is the pain you get when something very cold touches the roof of your mouth.

It is supposedly the most common cause of head pain; at least, according to the seminal 1988 textbook Headache, by Dr Neil H. Raskin. Although, Dr Raskin also found it was more common in migraine sufferers, with 93% of them experiencing it compared to 31% of a control group (see the reassuringly titled article by Joseph Hulihan in the British Medical Journal, “Ice cream headache: no need for abstinence” [PDF 159 KB]).

The pain appears to start in blood vessels in the mouth or sinuses, which rapidly contract when cooled and then dilate again when they rewarm. It’s then transmitted to the brain by either the trigeminal, glossopharyngeal or vagus nerve (opinions are divided on the culprit).

Diagram from Gray's Anatomy showing the trigeminal nerve, which carries signals between the brain and most parts of the face (click to embiggen)
The trigeminal nerve, shown in yellow, carries signals between the brain and most parts of the face. The glossopharyngeal and vagus nerves, not shown, largely serve the throat and chest, respectively. (Gray's Anatomy of the Human Body, 20th edition)

The problem is that each of these nerves serves many other parts of the head – like the forehead in the case of the trigeminal, or the membrane around the brain for the glossopharyngeal – and the brain misinterprets the signals as coming from one of these other areas. This is a phenomenon known as referred pain, which can also be experienced in heart attacks when people feel pain in the neck, shoulders or back instead of the chest.

There are a few treatments recommended for ice cream headaches, like tilting your head back, pressing your tongue against the roof or your mouth or drinking a warm drink. But for most people they’ll go away themselves some time between 20 seconds and 5 minutes – although for an unfortunate few they’ve been known to trigger migraines.

But as I mentioned before, it’s also the main drawback for a newly “discovered” method athletes can use to stave off overheating. Drinking “ice slurry” – basically slurpies – allows people to run for longer in hot weather and endure a higher body temperature, compared to those who only have a cool drink (Siegel R, Maté J, Brearley MB, Watson G, Nosaka K & Laursen PB 2010, “Ice slurry ingestion increases core temperature capacity and running time in the heat”, Medicine & Science in Sports & Exercise, vol. 42, no. 4, pp. 717-725, doi:10.1249/MSS.0b013e3181bf257a).

More recent follow-up research by the same group compared the ice slurry with full body immersion in cold water. Both methods were just as effective in increasing running time, but the slurpies were rather more convenient (Siegel R, Maté J, Watson G, Nosaka K & Laursen PB 2012, “Pre-cooling with ice slurry ingestion leads to similar run times to exhaustion in the heat as cold water immersion”, Journal of Sports Sciences, vol. 30, no. 2, pp. 155-165, doi:10.1080/02640414.2011.625968).

The one problem? 6 out of the 8 participants in the trial suffered from brain freeze.

Which just goes to show that even the most benign, natural-sounding treatments – or in this case, performance-enhancing drugs – can have unfortunate side effects. But still, remember that title from the British Medical Journal: “no need for abstinence”.

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