Newsflash: Read our science article, Cupulolithiasis: A Critical Reappraisal, at http://doi.org/10.1002/oto2.38
BPPV is the best understood form of vertigo, and usually goes away promptly with simple maneuvers. Sometimes, though, it can persist, and in those cases, a somewhat different and rare form is diagnosed, called cupulolithiasis. This means “stones on the cupula”, the cupula being the main sensor of the inner ear. In the time before we knew that ear stones—otoconia—moved freely in the ear canals causing vertigo, there was a theory that all the symptoms of BPPV were caused by otoconia that were attached to the sensor itself. Does this really happen?
The problem is that we can’t just look inside the inner ear and see what is happening. It’s deep inside the skull behind the eardrum, and so small it can fit inside a fingertip. From the time that one physician proposed cupulolithiasis as the cause, more than twenty years passed until the otoconia were seen moving in the canals during microscopic surgery. That observation proved how BPPV actually worked, and our many maneuvers are additional proof.
The cupula is an oval, very thin and transparent membrane that bulges back and forth like a trampoline as the fluid moves in the ear. It’s easy to suppose that if you had something heavy stuck to it, it might be indented in the direction of gravity. Since you can sense movement each time the cupula bulges, this would cause a major malfunction.
What is odd is that almost all the cases of cupulolithiasis involve the horizontal canal, the one that senses side to side head turns. It seems unlikely that just this sensor would be especially sticky and vulnerable when there are two others in each ear. The symptom is a horizontal spinning, quite violent, that reverses direction as you go from lying on one side to the other. It’s very nauseating, and often does not respond to maneuvers for H-BPPV.
In the next post I’ll show a photo of the cupula, and talk about the two different forms of H-BPPV, each of which requires a different treatment.