Twelve-year-old Maya Kaczorowski was out in the park one day with her parents, Janusz and Isabelle. It was a clear day in Hamilton, Ontario, and the family were discussing what Maya would tackle for her forthcoming science project. In common with many other 12-year-olds, Maya had no clue what to do. Her parents probed her interests. ‘What do you like to do most in the world?’ they asked. ‘Well,’ Maya said thoughtfully, ‘I like eating ice cream.’
Janusz Kaczorowski was no stranger to the scientific process. Then an associate professor at McMaster University in Ontario, he worked in family medicine, publishing a wide range of studies about health through the life course and how general medicine should be practised. He was very familiar with randomised controlled trials and soon began talking to Maya about how she could set something up to investigate her passion. They decided to focus on ice cream headache. Janusz had told Maya that cold-stimulus headache (or ‘ice cream headache’) happens to about one in three people, but Maya was interested in what happened to this incidence when people ate their ice cream really fast (Maya used the technical term: ‘gobbling’). Would an increase in ice cream headache experience in the gobbling group ‘justify Mum’s nagging’ to slow down?
Maya and Janusz set about designing a study. First of all they had to create a pre-study questionnaire to see who had experienced ice cream headaches at some point in their lives, and a post-study questionnaire to see who had experienced one during the study. Janusz then helped Maya to figure out how to randomise her participants. In the end, they put a green or red dot on each pre-study questionnaire and flipped them over. If you found you had a red dot, you had to eat 100ml (3½ fl oz) of ice cream in less than five seconds. If you had a green dot, you could take your time and certainly not finish within 30 seconds. Maya ran the experiment by herself, explaining what needed to be done to her 145 willing participants, all students at Dalewood Middle School in Hamilton. She learned some experimental hacks along the way – scooping the ice cream was slower and less precise than cutting it from a block – and that things sometimes got messy in the gobbling group…
After six eating sessions, Maya had all the data she needed. She put it all into the computer for analysis and her dad taught her how to test for significant differences. It turned out that gobbling ice cream more than doubled a person’s risk of developing a headache. These usually lasted less than 10 seconds yet were severe enough to cause 27 per cent of the gobbling group to clap their hands to their forehead in pain, as opposed to 13 per cent in the leisurely eating group. Interestingly, 79 per cent of her entire sample of schoolmates reported having experienced an ice cream headache before, which is higher than the figure random samples have shown up. This might be because children’s experience of pain and their recognition of it is usually quite simple, and based on cause and effect: ‘I ate the ice cream, it gave me a headache’. They also often eat it with great gusto. Another reason why there is a better recognition of ice cream headache in children is because in most cases they have few other pains to trouble them. How we recognise and remember pain is directly proportional to its effect on us, and this one makes itself known very forcefully and very fast.
Maya wrote up her study for the science fair. She didn’t get awarded a prize but she’s not bitter. She still got ice cream for her effort. Then her dad had the bright idea that they should write it up for the British Medical Journal (BMJ). Every year, the BMJ publishes a Christmas edition featuring some papers that address popular conundrums in society. For example, a notable recent contribution concerned the possibility that vasodilation may have caused Rudolph’s red nose, leading to a flurry of comments about the vascular system of reindeer noses in general. Maya’s paper (which she wrote with some ‘heavy edits from Dad’) was entitled ‘Ice Cream Evoked Headaches (ICE-H) study: randomised trial of accelerated versus cautious ice cream eating regimen’. It was peer reviewed for scientific rigour and published in 2002. By this point Maya was 13, making her the youngest author that I know of who has been published in the BMJ. That softened the blow of not winning the science fair!
The use (or abuse) of ice cream is not the only way you can demonstrate the cold-stimulus headache, but it is the most fun, which is why I endeavoured to replicate this experiment every year during one of the modules I was teaching at Durham University. I sometimes managed it, but more often than not I didn’t.1 One problem was that by the time we got to that part of the lecture, the ice cream was slightly melted and not as cold as it should be. The main issue, however, was that my participants were generally over 20 years of age and rather concerned about how they would look, which meant that getting them to gobble 100ml (3½ fl oz) of ice cream in five seconds was nigh on impossible. After a few years of this, I changed the experiment. Instead of ice cream, I brought juice boxes I had frozen in advance. By the time I needed them they were liquid again but still freezing cold. I also asked an assistant to squeeze all of the juice through a straw into their mouths either quickly or slowly. Boom, success! Groan city, but no chokers thankfully. The paperwork alone would have been a headache…
What is ‘brain freeze’?
Lots of people call this the ‘brain freeze’ headache, but it is a bit of a misnomer. Your brain is not actually frozen. If it were, it simply wouldn’t work and you wouldn’t feel anything at all, or you might in fact be dead. (Although as a coroner friend of mine likes to say, you’re not dead until you are warm, sober and dead. If your body is freezing cold, it slows down your metabolism to make your heartbeat much slower. If you are drunk, your heartbeat becomes faint, erratic and hard to hear, and your respiration slows down. Together, these two biological phenomena can make a body appear dead when it isn’t.) While death by ice cream may be a wonderful way to go, it is pretty impossible to achieve unless maybe through obesity-related illness. Even more curious, the phenomenon is not restricted to ice cream or cold juice.
Surfer’s skull
The phenomenon of ‘brain freeze’ is not restricted to those who gulp down ice cream or cold juice – it can happen to surfers and others who spend time in cold water, too. I often watch the surfers riding the waves near where I live, amazed that they can tolerate the chilly conditions. Curious about how they cope, on a cold March day in Saltburn-by-the-Sea, when the prevailing onshore wind had made conditions perfect, I intercepted a surfer called Mike as he came out of the waves and onto the beach. He wore a full wet suit with a neoprene hood on his head, boots on his feet and gloves on his hands; only his face was exposed. As a cold soul myself, I enquired as to his motivations for going out into the freezing North Sea in March. ‘The buzz is amazing,’ he said. Apparently the tides at that time of year, coupled with the wind direction, result in waves that are unrivalled anywhere in the world, and he has ridden them all. ‘But, aren’t you cold?’ I asked. He gestured to his kit. ‘No chance, not while I’m out there,’ he said through chattering teeth (clearly dry land was the cold place), ‘but the brain freeze is a killer.’
Even though Mike wasn’t drinking from the North Sea, the very cold water was still getting into his mouth, where the temperature differential between the cold water and his nice warm neoprene-ensconced body could be as much as 30ºC (86ºF). Surfers tend to breathe through their mouths and so the water shoots in, in much the same way as juice through a straw, causing agonising pain in the temples. Mike even said the intense pain was the main reason he falls off his board, as his body temporarily stops functioning. Yet he and countless others carry on regardless – clearly, the buzz is worth the brain freeze!
Contrary to popular belief, the stabbing pain that you feel in your temples is not caused by sensitivity in your teeth but rather by overactivation of the sensory receptors in the roof of your mouth. Much of this has been described through painstaking investigation with crushed ice that Robert Smith did through the 1960s.2 What Robert showed was that when ice touched the back of the roof of his mouth, otherwise known as the palate, pain came on around 20 seconds later as a stabbing, piercing sudden-onset sensation in the temple area above the eye closest to where the ice was located. Putting the ice anywhere else in his mouth didn’t create the sensation. This is because the palate is the only part of the mouth that doesn’t move, meaning it can give a really good indication, that’s stable over time, of the temperature of the food or drink that happens to be in your mouth. This is important because substances that are too hot or too cold might cause damage to the soft tissue in your mouth, impairing your ability to taste properly. Our brain therefore needs to get some trustworthy indication of the temperature of substances in the mouth.
The gobbling that Maya investigated causes ice cream to be forced right to this sensitive zone at the back and top of the mouth, and the same is true of the cold juice that was squirted into the mouths of my students and the freezing seawater that enters surfers’ mouths. Given the anatomy of the mouth and its connections to the brain, Robert concluded that the pathway involved is the sphenopalatine ganglion. This takes its name from the fact that it is located between the sphenoid bone (‘spheno’-), which is behind your nose towards the front of your face, and the palate (-‘palatine’); hence ‘sphenopalatine’. A ganglion is a nerve bundle. This is where all of the cell bodies, or engines, of the nerves are bunched together, and it connects directly with something called the ‘trigeminal pathway’ (see below), which brings pain signals from the head and face to the brain. Activating this pathway, for instance by bringing something very cold into contact with it, makes your blood vessels dilate to restore the temperature and heal any damage the cold may have done, and this in turn tugs on the trigeminal receptors on the blood vessels as they get bigger. But why is the pain all the way up in our temple? Why is it not in our mouths?
To understand this we need to know something about ‘referred pain’, but let’s start with thinking about the trigeminal nerve. This is a cranial nerve (a nerve that emerges from the brain) that controls all of the musculature in the face and head (including the smooth muscle in the blood vessel walls) and senses what is going on in the skin and musculature of the face, too. For example, it brings commands from the brain for things like the muscles of mastication (for biting and chewing) and expression (frowning and smiling) and takes sensory information back up to the brain, including touch and pain sensation. It’s the largest of all the 12 cranial nerves and has three pathways in twinned directions either side of the face – hence its name (tri- ‘three’, geminus ‘twinned’) – and has dense pathways to the mouth and nose and also over most of the skull.
When the sphenopalatine ganglion is activated, the message is carried by the trigeminal nerve up to the brain, where it is lumped together with signals from other areas of the face. Your sensory system can’t distinguish between these inputs and so we typically feel the pain in the temple area. Your body gets confused in other areas of your body, too. Much the same issue occurs when you feel pain in your heart from lack of oxygen, for example. Those signals are lumped in with the sensory information from your left arm and jaw, and so your brain feels the pain as if it were coming from there. Left arm and jaw pain are thus key symptoms of a heart attack.
There may, however, be a more direct reason why we feel pain in the temple region. In 2012, Jorge Serrador from Harvard Medical School asked participants to suck ice-cold water in through a straw and direct it to the back of their palate. They were asked to raise their hand when they felt the brain freeze come on. The researchers used ultrasound to track what was happening in the anterior cerebral artery – one of the main blood vessels bringing blood to the front of the head, which passes just behind the eyes. They saw a big increase in blood flow, caused by dilation of the blood vessels, before the participants raised their hand. Presumably it is this dilation that underlies the pain we experience. Once the anterior cerebral artery had returned to normal, participants indicated that they no longer felt pain.
So, we can say that brain freeze, or more specifically, the cold-stimulus headache, is caused by two things:
1 Overstimulation and referred pain from the palate. Since the response to pain in the body is always dilation, in order to bring all of the healing substances of the body to bear on the problem, the result is head pain.
2 A rush of warm blood to the head in order to keep everything functional. That rush of blood tugs on the trigeminal nerve receptors in the blood vessels themselves, also causing more pain, albeit through a whole other pathway.
This is why the cold-stimulus pain doesn’t happen immediately – it takes a while for your brain to perceive what is happening in your blood vessels as pain. This pain lasts as long as it takes to regulate your blood flow. Usually by 10 (or maybe more) seconds after you have introduced the offending cold intruder to your buccal cavity (otherwise known as your mouth; ‘shut your buccal cavity’ stops any argument, period. You’re welcome!) you will feel normal again. Thankfully, this two-pronged process is relatively brief. As we will see in the following chapters, some headaches are not so fleeting.