January 11, 2017
It's not uncommon as a kid to want to twirl about in the backyard to the point of dizziness, or take a ride on the merry-go-round at the park. What's not often explained, however, is what's actually happening in your body as the world starts to spin -- or, moreover, whether it's advisable for your health.
To get a firm explanation, we reached out to Jefferson Health's Dennis Fitzgerald, neuro-otologist and assistant professor in the department of otolaryngology.
Why is it that when you spin you get the sensation of dizziness?
The spinning of the merry-go-round, for example, is detected -- the first thing that happens is your inner ear detects that you're spinning on the merry-go-round and your eyes are telling you that you're spinning, but not in the same way your inner ears are telling your brain that you're spinning. And so you have a mismatch of information. And when there is this mismatch of information, and especially then when the merry-go-round stops, your inner ears no longer detect the spinning. As the brain thinks you're still spinning but your eyes don't tell you that you've stopped. So, that's the mismatch between what your inner ear is telling you and what your vision is telling you.
This also is the basis of motion sickness. For example, if you're riding in a car and you look down at a book and you're reading, your vision tells you that you're not moving. But your inner ear is sensing that you're moving through space. And so you have the mismatch of info between what you're looking at -- your brain thinks you're not moving because your vision tells you you're not moving, but your inner ear tells you you're moving. Now, we all have different susceptibilities to motion sickness. So, this can be more tolerated in some than others. And people who have migraines have a very high degree of susceptibility to motion sickness. 'Migrainers' have hypersensitive reactions to sensory input. Whether it's vision, or touch, or smell or motion sickness – 'migrainers' especially will have a very high degree, or instance, of motion sickness.
Crazy that the inner ear is such a key player in this. What's the reason?
Well, it's a major sensory input to the brain about where we are on earth, and whether we're moving or not moving. The second piece of information that gets sent to the brain about those things is vision. And the third and least important of the three is info we get from feet and ankles about whether we're standing on a flat or not-flat spot on earth. The primary input to the brain about our balance system comes from the inner ear.
Interesting that even though we might consciously recognize we're not spinning anymore, we're still waiting for senses we're not controlling to catch up.
There is a storage mechanism. For example, if you go on a boat and you're on the boat for the first period of time, you feel the rocking of the boat, but eventually, you stop perceiving the rocking because the brain stores the fact you're rocking and not standing still. And when you get off the boat and stand still on a flat surface – not moving – the brain still is used to rocking and slowly adapts to the fact you're no longer rocking. Now, that adaptation in some people does not take place for weeks or months.
Any rhyme or reason to how long it takes your brain to adjust?
Every person has their own built-in mechanism and susceptibility, and for all these things 'migrainers' have a much higher susceptibility.
Any danger to having a kid on the merry-go-round and getting dizzy? They do it for fun, after all, and most parents are happy to oblige.
No. It may. If they're dizzy, they may throw up. But it's not going to hurt them in any way.
Anything to add?
I guess I can talk about dizziness all day long. But I've been doing this business, taking care of dizzy patients, for 34 years -- so I've had to explain this thousands of times to patients. I'm used to doing it and doing it in simple terms people understand. Part of my job is being an educator as much as a treater of disorders.
I imagine this science hasn't changed much through the years?
I think that's probably true. We've probably understood the mechanisms for decades, but it is something the average physician doesn't want to deal with because they don't understand it very well and they get nervous about taking care of people with vertigo and dizziness. There are a few hundred of us in the country who do this as our main profession.
Do you mean motion sickness when you say dizziness?
Motion sickness, dizziness, vertigo -- vertigo is not a disorder, actually, it's a symptom. The definition of it is the 'illusion of motion.' And the most common disorder that causes the illusion of motion -- and most of the time it's the illusion of spinning -- is a disorder that has a big long name, which is benign paroxysmal positional vertigo, that was shortened to be BPPV. Six percent of the population every year [experiences BPPV]. Most people think they're having a stroke or heart attack when it first hits. But it's little particles of the inner ear that break loose and slide into a spot they shouldn't be. And then when you roll over in bed or get out, the room begins to spin and it's very alarming feeling. This particular event ... usually happens from some head injury.