Ending Vertigo Today

Our latest BPPV paper

My latest paper with co-author Olivia Kalmanson just came out and can be read here. It’s about an ongoing confusion regarding how BPPV (positional vertigo) causes its symptoms. This confusion has been going on for over 50 years now. This kind of problem is very common in science. It begins when a prominent researcher publishes a theory that will turn out to be wrong. However, because the person is prominent, people are afraid to criticize the mistake. In fact they keep putting it forward long after other, less well-known scientists have come up with a much better explanation. Decades go by, long after the first theorist is in the grave. Eventually the sheer weight of evidence crushes the incorrect theory, upholding the self-correcting nature of science. Sadly though, much time is wasted.

The old theory we are talking about in our paper is cupulolithiasis, the belief that the particles in the inner ear that cause BPPV attach strongly to the cupula, the spinning sensor of the inner ear. These particles are heavy, causing the sensor to respond to gravity. Seems quite reasonable at first. Part of the reason this caught on easily was misunderstanding the anatomy of the sensor.

This is an older anatomy picture that was how most people visualized the sensor in the past. The cupula was pictured like a little flame, with a wide base and a narrow tip that swept from side to side. It was this sweeping movement that was thought to move the hairs at the base, sending electrical signals that the head was moving. It seems simple to just stick a clump of particles on the tip, which would cause it to bend with gravity.

This isn’t how it looks or works. The cupula is an oval membrane that is attached at the base, the ampullary crest in this picture, but is also attached all around its rim to the ampulla, a sphere that surrounds it. It’s more like a trampoline than a flame. The reason this has been hard to understand is that, first, the ampulla is only about ¼ inch across so all of this is nearly microscopic. Secondly, it is completely encased in the bone of the skull, so it is not seen unless you use a drill. Finally, it is nearly transparent. No wonder the anatomy is confusing.

Here is a more modern view:

Viewing straight on at the cupula “Cup” , you can see it is an oval attached all around the edge to the ampulla “Amp”. The canal “Can” that contains the crystals in BPPV is pointing at it from the back in this picture. Crystals couldn’t attach to the tip because there is no tip. If they stuck anywhere, it would have to be the middle. They would have to be very sticky indeed to stay on a constantly flexing mat, resisting the pull of gravity.

The theory that particles stick on the tip and move the cupula was published in 1969 by Schuknecht, who was a very prominent and intelligent physician scientist. It wasn’t a bad way to explain BPPV at the time, and many of the other things he figured out were good. However, about a decade later, McClure and his team came up with a better solution: that crystals were moving back and forth in the canal, working like a piston that could move the canal fluid back and forth, and this would flex the cupula like a trampoline. Loose particles could be rotated out of the canal, and this was proven by Epley, who invented a curative maneuver. They were correct, but by then almost everyone was still enamored with the cupulolithiasis theory and respectful of its author. The better theory was not accepted for another decade. Even then, cupulolithiasis remained popular too, especially for BPPV that didn’t respond well to maneuvers.

Over time it’s become clear that these resistant cases can be explained by blockages that form in the canals near the ampulla or at narrowings, trapping particles. They don’t need to stick to the cupula to cause symptoms. So cupulolithiasis is no longer needed to explain BPPV.

Even though it’s unlikely that two totally different mechanisms for a disease will turn out to be true, there are still articles being published about cupulolithiasis 56 years later. The problem, though, is that everything in BPPV can now be explained by particles in the canal. Belief in cupulolithiasis is holding the field back. This is important because the treatments needed would be different. If you have loose particles in the canal, you can move them out with maneuvers. If there is a blockage, some vibration on the head can help break it up. If they were attached to the cupula, however, this would not necessarily work. Finding an effective treatment depends on truly understanding how the system works.

Aural vertigo comes in two flavors

By far the most common cause of inner-ear-related vertigo is BPPV, with brief spins brought on by lying down or rolling over in bed. However, there are many other causes of vertigo, and it can be very confusing to figure out which one is the problem if you have something more complicated than BPPV. One way to narrow this down is by looking at two very broad categories of vertigo, so that you can decide which of these you have. This quickly helps you narrow down the diseases that may be affecting you.

Your brain creates the sensation of turning every time you move your head. When you are not moving, each ear generates a low but steady flow of electrical signals that is received continuously by the brain. This symmetric flow lets your brain know that your head is completely still. If you move your head, the flow of signals changes instantly. If you turn your head to the right, your right ear “turns on” and increases the flow of signals, while the left “turns off”, and shows a decrease. Your brain interprets this change in the symmetry of the signals as a turn—a right turn if the right ear is increased and the left ear is off, and a left turn if the left ear is increased while the right ear signals decline. That’s what happens with normal head turns.

Vertigo—the feeling of spinning when you are not turning—happens when the symmetry of the two ears is broken even though you are not moving, for example if one ear becomes turned on while the other is not. This means there are two flavors of vertigo. The first flavor is vertigo brought on by an ear that suddenly gets turned on, increasing its signals. If you are not turning, both ears should be sending the same low flow of signals, so if one suddenly starts firing more, this asymmetry will be felt as a turn toward the abnormal side. If your right ear suddenly increases its firing, you’ll feel spinning to the right.

The second flavor of vertigo is spinning brought on by a sudden decrease in one ear’s signals—the ear turns off. Again, the brain feels spinning any time there is asymmetry between the ears. So, an ear that turns off makes the other ear’s signals look too fast, and you feel a spinning toward that normal ear. A left ear that shuts off will cause a spinning feeling to the right for this reason. Notice that a spin to the right can come from EITHER the right ear being turned on or the left ear being turned off. How can you tell whether it is due to an ear being stimulated vs. inhibited?

One way to determine this is to look at the speed of the feeling of spinning. The key is that both ears have a fairly low flow of signals when you are not moving. If you inhibit or turn off one of the ears, the other unaffected side does not increase—the flow is still fairly low from the good ear. When your head is still, this will give you a constant, steady, unvarying feeling of spinning. The room spins in a smooth fashion, not very fast. You can usually still see things around you when having this vertigo, even though they will shift constantly. Rather boring—the plain vanilla kind of vertigo. You will be able to make this spinning increase by moving your eyes to one side, which is an important clue that you have one ear that is not working. It will also worsen when you make a sudden head turn.

The situation is very different if you have one ear that becomes “too turned on”. The natural sensor of the ear can sense extremely high rates of acceleration, so there’s no upper limit to the speed of the spinning you will feel. Fortunately, stimulatory vertigo is usually very short. This is the flavor of vertigo caused by BPPV, when you directly stimulate one spinning sensor in your ear. It’s not boring at all. It’s thrilling (but not in a good way). Not the sort of thing you can sleep through. The world spins and it feels like you’re going to rocket off the bed. How you move your eyes has no impact on this kind of vertigo.

Here are some diseases that cause each flavor of vertigo:

Stimulatory vertigo—ear too turned on: BPPV, semicircular canal dehiscence, fistula

Inhibitory vertigo—ear turned off: vestibular neuritis & viral infections, labyrinthitis, Meniere’s disease, autoimmune diseases, tumors such as acoustic neuroma, any loss of blood flow or trauma to the inner ear

It’s ironic that the most common cause of vertigo, BPPV, is stimulatory and so is more severe than the many other causes in the inhibitory category. Mercifully, BPPV is short and easy to fix with maneuvers.

BPPV treatment: Turning 45 degrees?

A positional vertigo patient struggles to understand how to do the maneuver for the right ear:

TURN HEAD TOWARDS ELBOW? Which part of head, the chin or the back of the head? Picture shows back of head towards rt elbow. I don’t see any 45 degree angle; the head looks almost in same plane as back in the picture. R U saying 45 degrees relative to the plane of the back so the chin points slanted down towards the floor?

The handouts are in our book and at the bottom of the blog webpage, and our videos can help too, but it’s always disorienting to figure out what that means when your head is upside down! The best way to understand how to correctly move your head is to first practice the head turn when you are upright.

If the right ear is the problem ear, sit in a chair and turn your chin toward your right shoulder, stopping when you are halfway there. A 45 degree angle is the halfway point to looking fully over your right shoulder. If you turned all the way, your chin would be almost touching your right shoulder, so you don’t want to go that far. You will do this same halfway-to-the-shoulder move when you are upside down.

An easy way to know you are doing this properly when upside down on your hands and knees is to turn until you are looking straight at your right elbow . This places your head near the correct 45 degree angle. Your head should be completely upside down, so the chin is not tilted much up or down, although tucking your chin under slightly can help move some deeper particles.

If your problem is in the left ear, you will want to turn your chin toward your left shoulder and to look at your left elbow when upside down.