The rhythm of throbbing pain
Is your pain a throbbing pain? Pain often has a pulsating quality, especially when it’s severe and acute. If you’ve ever thought about why it pulses, you probably assumed that it’s pulsating with your pulse. Heck, “pulsatile pain” is actually a clinical term used to describe throbbing pain that is assumed to be surging in time with the arterial pulse.
I have always particularly noticed the throbbing of infections — like a hangnail that’s gotten out of hand — and I always thought that I was feeling the blood pushing through the ultra-sensitized tissue.
But Mirza et al. checked that assumption… and got a fun science surprise.
They checked in a bunch of patients with jack-hammering dental pain, getting them to tap out the rhythm of their throbbing with a button… and discovered that their throbs were actually much slower than their heart rates, almost half the pace, just not in sync. They were clearly different rhythms! Not so pulsatile after all.
That’s a fascinating upset to conventional wisdom. (About a very minor thing, sure, but still…)
So what is setting the pace?
The authors took a crack at speculating about what was setting the rhythm of their subjects’ dental throbbing: “an emergent property, or perception, whose ‘pacemaker’ lies within the CNS.”
They confirmed the same pace difference in a follow-up study of a woman with a very different kind of pain, chronic migraine: her head throb was quite a bit slower than her heart rate (48 bpm vs 68). Analysis of her EEG showed that activity in the alpha range (8 to 12Hz) was linked to “greater throbbing intensity” — more alpha oomph came with more fiercer throbbing.
Reality is always messier than either the conventional wisdom or a slam-dunk of a debunk. The safe bet is that there are several kinds of throbbing pain. I doubt anyone will be checking them all anytime soon, so we can just enjoy the uncertainty indefinitely. But I definitely suspect that some of our throbbing pains truly are pulsatile. Like that infected hangnail, maybe. Ow … ow … ow … ow … ow…
This post is an excerpt from Pain is Weird.