Here’s a photograph of the cupula of a mouse, taken by Dr. Olivia Kalmanson at the University of Colorado. The cupula looks dark green because it’s transparent, so the background can be seen right through it. To make it easier to see, we’ve piled otoconia, the gravity sensor’s crystals, on the middle of it. They are indenting it like a pile of rocks would indent a trampoline. At the bottom of the picture is the crista, the base of attachment of the cupula that contains all the nerves and sensory cells that make the inner ear able to sense spinning.
When particles enter the horizontal canal, it creates a much worse form of BPPV (called H-BPPV). One reason is that this canal is the most important sensor for head movement. We tend to move our heads to the right and left more often and in larger swings than we move our heads up and down. The horizontal canal senses these movements and is accordingly more sensitive and causes greater dizziness if BPPV affects it. Vertigo that is horizontal also causes nausea and vomiting more quickly and more severely than BPPV in the usual, posterior canal form. The room will spin as if you are on a turntable, and your eyes will go back and forth horizontally, from corner to corner, if someone observes you.
This isn’t the only problem. In typical posterior canal BPPV, it doesn’t matter where the particles are located. They can easily be removed with the half somersault maneuver or other maneuvers. H-BPPV is different. There are two varieties of H-BPPV, depending on how far into the canal the particles have penetrated, and it requires different maneuvers to remove them.
We define H-BPPV by the direction the eyes move (nystagmus) during a spell, when you are viewed lying down on your back with the head turned to one side. The most common form of H-BPPV is called geotropic (“toward the earth”) which means the eyes tend to beat or jerk toward the ground. So if you’re on your back, with your head turned to the right, the eyes will beat toward the right. If you turn your head to the left, they will then beat to the left. In each case, they beat toward the floor. In this kind of nystagmus, the particles are located very near the opening of the canal, so it’s quite easy to turn the head and let them exit. The Gufoni maneuver is very quick to do and will resolve this type in seconds.
There is a rarer and more difficult form of H- BPPV to treat. This is the apogeotropic form (“away from the earth”). Instead of bouncing or beating toward the ground, the eyes beat upward toward the ceiling. When you lie on your back with the head turned right, your eyes will beat left; and if your head is turned left, your eyes will beat right. It is the opposite direction to the geotropic form from the point of view of the observer, but just as nauseating to the person with the problem. This form happens when the particles penetrate all the way around the canal and end up near the sensor of the canal, the cupula. Because they are so deep in the canal, it takes larger head rotations to remove them.
The apogeotropic form often seems to be hard to correct with maneuvers. This is usually because the maneuvers used don’t rotate the head far enough, but sometimes it can mean that particles have become stuck in the canal in a way that they can’t exit. Are they stuck on the sensor itself? Are the crystals in the photo now attached to the cupula? We’ll discuss this more in the next post.
Ending Vertigo Today 