Sitting in deep within your skull, alongside your snail-shaped hearing organs, are your inner-ear balance organs, also called your vestibular system.
To begin to understand what your vestibular system does, perform this simple experiment: Hold your finger out in front of your face at arm’s length. Now shake your head back and forth while looking at your finger. You can keep the finger in fairly good focus, can’t you? Now hold your head still and move your finger very quickly. You will see that it is much, much harder to keep a good focus on your finger. The clear focus that you are able to keep on your finger during the first part of this experiment demonstrates the incredible efficiency of your vestibular system.
Your vestibular organs sense the position and motion of your head. They are hooked up to a reflex arc in your brainstem that controls the position of your eyes. As you move your head, your brainstem automatically moves your eye muscles to keep them on your finger. We believe that the “purpose” of this arrangement is to stabilize gaze and allow us to keep things in focus while we are moving.
Your vestibular system has two parts, both of which are responsible for telling your brain where your head is in relation to the world. The first part is a tiny fluid-filled room with special “hair cells” lining the floor like a carpet. The cells are covered with calcium crystals which sit on the top of the microscopic hairs. When you look down the crystals are deflected forward and the hair cells move in the forward direction. When you look up, they go the other direction. This is how your body senses your head’s relationship to gravity. The “semicircular canals” splayed out from the tiny room-like curvy fluid-filled tunnels comprise the second part of the vestibular system. Each of these tunnels has a membrane stretched across it with a sensor embedded in it. The membrane bulges when the fluid in the hallway pushes on it from either direction. When you turn your head, the fluid within the tunnel will push on the membrane, and the sensor sends a message to your brain that basically says “I am turning.”
Your overall balance system, responsible for keeping you upright and moving freely through the world, is complicated. Balance, as a whole, really involves your brain putting together information from your vestibular system, but also from your eyes, your limbs and even some sensors in your neck. But when the inner ear is affected, balance problems can be quite severe. When something is wrong in the vestibular system, the brain receives the wrong information about head position and motion, and cannot put it together accurately with information from other sources. The result is instability or a sense of motion which we call vertigo.
Viruses Can Cause Motion Sickness and Spinning
One of the most dramatic problems happens when a virus affects the vestibular system causing it to suddenly malfunction. People with this problem will have a sudden onset of a wild sensation of spinning that will last up to several days. During this time, they may be completely unable to walk. They usually suffer from severe motion sickness with nausea and vomiting and often need in-patient medical care.
Benign Positional Vertigo
The good news is that vestibular problems of the magnitude are much less common than what we call benign positional vertigo. Benign positional vertigo is an extremely common disorder that has to do with the calcium crystals that sit on top of the hair cells in the tiny room. Sometimes these crystals will become dislodged from their position on top of the hair cells and will go floating around inside the semicircular “tunnels” nearby. When these crystals find their way into one of the semicircular canals, they can cause some abnormal signals. For example, if the patient looks up, the calcium crystal in one of the tunnels may tell the brain that their head is turning. They will usually experience a brief spinning sensation which usually lasts less than 30 seconds and then resolves. This is because the patient will become still after the sensation of motion starts, and the crystal will settle down. The classic symptom of someone with benign positional vertigo is that they will get their symptoms while rolling over in bed. If patients tells us that they have problems rolling over in bed, we are just about certain that they have benign positional vertigo.
Most of the time, benign positional vertigo is fairly easy to treat. An otolaryngologist or a vestibular therapist, which is a physical therapist with special training, can do tests to discover exactly which semicircular canal contains the errant crystal. They can then take the patient through a series of head motions that float the crystal back out of the semicircular canal and into the center room. When this is accomplished, the patient’s symptoms will resolve. Patients can learn these positions on their own as well so that they can repeat them at home should another crystal find its way into the wrong place.
Because benign positional vertigo is so well treated without any sort of medication or further testing, there is no reason for patients to put up with spinning when a visit or two to a specially-trained physical therapist can give them so much more control over their symptoms.
There are other problems of the inner ear that can contribute to imbalance and feelings of spinning or motion. The role of the otolaryngologist is to help sort out the causes of vertigo and help the patient on the road to recovery.