Is throbbing pain your heartbeat?

13 September 2016

Interview with

Kat Arney, The Naked Scientists

In this regular mythconception, and this week Kat's been looking into a painful Headacheproblem.

Kat -   It's something I'm sure most if not all of us have experienced at some point: that awful throbbing pain that comes with a headache, toothache, or even just a bad knock, trapped finger, nasty cut or other injury. Thud, thud, thud... Owwwwww.  It's often assumed that because this is such a regular, pulse-like throbbing it must be linked to the heartbeat. It certainly makes sense that there might be pulsations of blood flowing through an injured or sore area, beating against sensitised nerves and creating that horrible throb. But although it's a logical assumption, dating back as far as the Greek philosopher and scientist Aristotle, it's a wrong one.

Dr Andrew Ahn and his colleagues at the University of Florida managed to disprove the idea that throbbing pain is linked to the heartbeat with an incredibly simple experiment - they simply found people suffering from throbbing pain, monitored their pulse rates and the patterns of the throbs, and compared the two. And they just don't match up.

Ahn's team have actually published two papers looking at the relationship between throbbing pain and the heartbeat - one with people suffering for migraines, and the other with people with severe toothache. One can only imagine how generous these volunteers must be to even want to take part in research while suffering agonising pain. What they did was very simple - just measured each person's pulse while asking them to tap out the rhythm of their pain throbs on a computer or table.

For the migraineurs, their heads throbbed at an average of around 62 beats per minute, while their heart rates were an average of 80 bpm. Even for people who had fairly similar heartbeats and pain pulses, they fell in and out of synch, suggesting they aren't linked. Similarly, for the people with tooth pain, their average heart rate was 72 beats per minute, while the average throb rate was just 44. Yet, when the researchers looked closely, the throbbing clearly had its own rhythm, so if it's not caused by the pulse of blood, it must be caused by something else. But what?

Using a technique called electroencephalography, or EEG - which is a way of measuring electrical activity in the brain - Ahn found that the throbbing correlated with a particular pattern of brainwaves called alpha waves, which run through the brain at between 7.5 and 12.5 cycles per second. It's not clear exactly what alpha waves do, but the discovery that they might be linked to throbbing pain is an intriguing one.

Although it might seem like a simple experiment, proving that the pulsing of blood through a site of pain isn't responsible for the throbbing is an important observation. Some medical professionals still use the presence of throbbing as a proxy for an injury or damaged tooth still having a blood supply, when in fact it may not be the case at all and could be misleading. And as anyone who's suffered from severe pain will know, the current arsenal of painkillers don't always work that well, and can have side effects including addiction. So discovering that the throbbing is linked to certain brainwaves could one day lead entirely new ways to tackle pain. Now that's a real brainwave!

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