Positional vertigo is when a patient complains that every time they make a specific movement, they get this brief duration vertigo where they spin around. So for example, a patient may say, every time I roll over to the right, I feel very, very spinny, but it only lasts about 20 or 30 seconds. And if I make that same motion again, I feel spinning again, but it's not as bad. So what happens is, as they repeat the movement, it sort of fatigues out and it gets less and less. Every time what's actually happening in the ear is that there are these little salt, light crystals that live within the organs of the vestibular system. And they give us information about where we're positioned in space, if we're up and down, left and right, these little crystals can become dislodged and they roll into a different part of the balance system. So maybe you have a crystal that tells you about left and right. And it falls into the part of the balance system that tells you about up and down. So when that happens, when you roll over all of a sudden, your brain can't make sense of it and you feel very spinny as well.