Thread by @RGottliebSmith

1/🧵
What’s going on in the 🧠 that causes motion sickness – and what’s the link with #migraine?

A #tweetorial about motion sickness, the importance of matching, and why serotonin matters

#MedTwitter #NeuroTwitter

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First, let’s review some structures of the vestibular system that help us sense body movement:

1⃣ Semicircular canals = angular acceleration
2⃣ Otoliths (utricle & saccule) = linear acceleration & head tilt

📷: cell.com/current-biolog…

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The 🧠 combines this vestibular input with visual 👀 & proprioceptive input to assess motion

➡️ This is where the importance of matching comes in

...So what happens when the inputs don't match?

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'The neural mismatch theory' = 🧠 receives conflicting info from vestibular, visual & proprioceptive systems

2 main categories of mismatch:
1⃣ Semicircular canals v. otoliths
2⃣ 👀 v. vestibular/proprioceptive

pubmed.ncbi.nlm.nih.gov/23615033/

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Example of semicircular canal v. otolith mismatch: 'vestibular coriolis' reaction*

*The fancy term for what happens if you're spinning in a chair in a horizontal plane and move your head along another axis (like forward or backward)

pubmed.ncbi.nlm.nih.gov/23615033/

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Example of 👀 v. vestibular mismatch: reading in a car

Your 👀 tell you you're not moving, but your vestibular system says otherwise

...All of these can lead to the classic symptoms of nausea/vomiting, pallor, cold sweats

7/
Motion sickness is particularly common in kids, and we often see it as a precursor to #migraine

What's the 🔗?

There are a few ideas, including a hypersensitive vomiting center & central hypersensitivity, and some interesting observations involving serotonin

8/
🔽 tryptophan - a precursor to serotonin - 🔼 motion sickness in controls, similar to others w/ migraine
pubmed.ncbi.nlm.nih.gov/16116130/

& pretreatment w/ rizatriptan - a serotonin (5-HT1) receptor agonist - 🔽 motion sickness in people w/ migraine
pubmed.ncbi.nlm.nih.gov/20862509/

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So serotonin may help with motion sickness!

(But somehow I don't want to personally test this on Thanksgiving after eating lots of tryptophan...)

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In summary, 2 major ideas:
💡 A theory behind motion sickness: 'neural mismatch theory' = conflict between vestibular, 👀, & proprioceptive systems
💡 Low serotonin may be a connection between #migraine and motion sickness