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Fainting follow-up: vasovagal syncope versus the vagal manoeuvre (plus a vagus-hype glossary)

 •  • by Paul Ingraham
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I’ve only fainted once in my life: I was on Mayne Island, one of the beautiful Gulf Islands of British Columbia, Canada. I had been out hunting oysters in the sun. When I got back to the farm where I was working at the time, I tried to shuck my first oyster with a screwdriver… and it slipped and plowed into my palm. Oops! Out like a light!

I felt like a robot shutting down, and then verrrrry slowly rebooting. I still remember the view of the kitchen floor as I tried to remember who I was. Good times!

That was classic vasovagal syncope — fainting — with all three of its classic triggers: seeing blood, stress (exhaustion), and prolongued standing.

Anyone else got vasovagal syncope stories?

Why is it the “vagal” manoeuvre?

My fainting story eases us into my rather dry idea for a post: clarifying the confusing terms and concepts related to the vagus nerve, and reflexes, and fainting. This began as a “simple” follow-up to a post I wrote in early September about “vagus massage”, AKA the vagal manoeuvre, and it’s many alleged benefits (relaxation?) and risks (death?!). But the vagal manoeuvre doesn’t actually have anything to do with the vagus nerve!

So why is it called that? Seriously! It’s bizarre.

I originally offered just one half-hearted reason for that odd naming glitch, but then thought of a better one later: the so-called “vagal” manoeuvre may not have anything to do with the vagus nerve, but it does have something to do with fainting, because it can cause a faint by lowering blood pressure.

So the vagal manoeuvre misnomer may be thanks to the fainting link and the more familiar term “vasovagal syncope.”

That’s just a guess. Researching the etymology of “vagal manoeuvre” would take more time than the topic deserves here. But trying to explain the confusing overlap all these terms? That might be more useful. Tricky. But useful. Plus it’s nearly impossible to understand my “simple” follow-up without …

A glossary of terms related to vagus nerve hype

  • Vagus nerve — A mighty nerve that descends from the brain and plugs into … practically all your guts. It regulates visceral function, and is often touted for its potential to relax and restore homeostasis. Vagal therapy hype goes like so: “because your vagus nerve regulates everything, maybe it can fix almost anything if we just tickle it?” Electrical stimulation of the vagus might actually be useful for chronic pain (which is why I’m writing about any of this), but all other “vagus stim” methods are super hand-wavey.
  • Syncope — Medical term for “fainting.”
  • Reflex syncope — A category of fainting that includes both kind of syncope described below, plus “situational” syncope (fainting from a variety of other triggers, most famously after peeing).
  • Vasovagal syncope — The most familiar kind of fainting (e.g. triggered by stress). Vaso for blood, vagal because it’s mediated by the vagus nerve. Not the same as the vagovagal reflex.
  • Vagovagal reflex — A complex reflex that mainly kickstarts digestion in response to distension of the gut. Included here in contrast to “vasovagal.”
  • Carotid sinus baroflex — A blood-pressure dropping reflex triggered by pressure (baro) in a wide spot (sinus) in the carotid artery, where it forks beside the Adam’s apple. Controlled by the glossopharyngeal nerve, not the vagus!
  • Vagal manoeuvre — Triggering the carotid sinus baroreflex with massage. Weirdly, this has nothing to do with the vagus nerve, despite the name (maybe because of conceptual overlap with vasovagal syncope). It can be surprising and unpleasant, but is mistakenly described as “dangerous” by many professionals, maybe to hype the “power” of vagus nerve stimulation — a mistake based on another mistake. Derp!

Clear as mud?

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