One Thing From the Book

I’ve always thought balance was just the vestibular system: the semicircular canals in your ears. Balance is more than that—it also involves your proprioception, your vision, even your neck muscles. All of these work together to produce balance. Therefore, we don’t have a sense of balance; we’re simply balance.

The other thing I remember: The story of Ian Waterman who completely lost his proprioception and could no longer move, even though he had no loss in muscles and retained all his nerves, etc. He managed to retrain himself to stand and walk simply from using his vision and concentration.

My notes

The semicircular canals contain endolymph, a fluid slightly thicker than water. It’s about the consistency of an average beer. Move your head in any direction and the endolymph in the associated semicircular canal flows in the opposite direction. Each loop of the semicircular canals has a bulged end called the ampulla, which contains a structure called the cupula. The cupula looks rather like a flower bud and is filled with an almost jelly-like substance and a bunch of miniscule, sensitive hair cells. These hair cells are key to keeping balance because they send positional information to the large vestibular nerve, which in turn feeds that information to the brain.

She had also been successfully treated for the most common disorder of the inner ear, benign paroxysmal positional vertigo (BPPV). Remember those tiny ear crystals that are pulled by gravity in the utricle and saccule? Sometimes one or more of the crystals comes loose, maybe because of a blow to the head or an infection but usually just as a happenstance of aging. The crystals dislodge from the membrane, become floating debris, and eventually dissolve. But sometimes some of those ear rocks from the utricle find their way into one of the semicircular canals, where they mess with your balance. Because the semicircular canals send signals to the brain about the movement and position of your head, even small bits of debris can change how positional shifts are registered. The extra weight of those tiny ear rocks alters how the fluid moves within the canal, so the vestibular system ends up sending false signals to the brain that you are moving, even when you are standing still. That means that brain signals don’t match actual head movements.

Remember those tiny ear crystals that are pulled by gravity in the utricle and saccule? Sometimes one or more of the crystals comes loose, maybe because of a blow to the head or an infection but usually just as a happenstance of aging. The crystals dislodge from the membrane, become floating debris, and eventually dissolve. But sometimes some of those ear rocks from the utricle14 find their way into one of the semicircular canals, where they mess with your balance. Because the semicircular canals send signals to the brain about the movement and position of your head, even small bits of debris can change how positional shifts are registered. The extra weight of those tiny ear rocks alters how the fluid moves within the canal, so the vestibular system ends up sending false signals to the brain that you are moving, even when you are standing still. That means that brain signals don’t match actual head movements

BPPV is the most common cause of dizziness and vertigo, accounting for about 20 percent of all vertigo cases and affecting more than four million people in the United States each year.

Sitting up on the side of your bed, turn your head forty-five degrees to the affected side (the side that seems to make you feel the worst). With your head still in the forty-five-degree turn, lie down quickly. (Some doctors recommend hanging your head over the edge of the bed, but others say to lie flat.) This will make you feel really sick, but don’t worry the sensation goes away within about fifteen seconds. Stay in that position for thirty to sixty seconds, then turn your head so that it is forty-five degrees to the opposite side. Wait another thirty to sixty seconds. Then turn your body and head together in the same direction so that you are lying on your side with your head pointing down toward the floor at a forty-five-degree angle. (To do this last move, pretend that you have a stiff neck that can’t move when you turn your body, your head moves with your body, without independent movement from your neck.) Stay that way for another thirty to sixty seconds. Finally, keeping your head turned, sit back up in the original position. You can look forward again, but keep your head level and sit still for about ten minutes.

When you shake your head side to side, the thick endolymph fluid in the horizontal semicircular canals (one on each side of your head) gets displaced, moving the tiny hair cells at the end of the loops, which send signals about your head position to the brain. The brain reacts and sends simultaneous signals to the eyes, telling them to move in a manner and speed that is exactly proportional to the head movements

In addition, it highlights another balance revelation—the muscles of the neck play a role in balance and dizziness. I hadn’t expected that; it didn’t dawn on me that it could be true until Dr. Piker explained the VEMP. But the neck-balance relationship affects a lot of people. In the 1980s scientists began talking about cervicogenic vertigo, debating whether it was a real condition. Thirty years later, the debate continues. There are no tests that can pinpoint a diagnosis of cervicogenic vertigo. It is only diagnosed by a process of elimination.

Even then, some physicians hold the position that the condition must be caused by some other linking factor, such as mild brain injury. Still, there is an abundance of literature and anecdotal reports from clinics about vertigo and/or dizziness that began after a whiplash injury, chronic neck muscle spasm, or athletic injury involving the neck (such as injury from heading the ball in soccer, or a helmet hit or just about any other injury from playing football).

Balance begins with knowing which way is up. When you awake in your bed and open your eyes, you know that you are lying down and that the world hasn’t suddenly shifted ninety degrees. It might seem self-evident, but it actually takes a combination of cues to allow you to come to those conclusions. First your brain gets cues from the vestibular system, especially the gravity-sensing tiny crystals of the inner ear, which are pulled downward toward the earth regardless of your body orientation. Second your eyes visually scan the environment for more clues the fan is on the ceiling, so you know, logically, that up is where the fan is. And third your proprioceptive system tells your brain how your body parts are oriented in relation to each other and to the rest of the world.

When wind turbines were erected near her home, she began to hear reports from neighbors of a clear cluster of symptoms: migraine; motion sickness; vertigo; noise, visual, and gastrointestinal sensitivity; and anxiety. (Other researchers also list sleep disturbance, rapid heart rate, visual blurring, panic attacks, and ringing in the ears as Wind Turbine Syndrome symptoms.)

Researchers acknowledge that some people living near wind farms have vestibular symptoms, but the exact cause of the illness cannot be definitively tied to the turbines. A review article published in 2011 concluded that current research cannot point to a direct causal link between wind turbines and physiologic symptoms

Theirs was the first lab in the world to show that when people have hearing loss, giving better hearing cues can improve balance. What that means is simple yet revolutionary: Balance improves when people with hearing loss use hearing aids. As Dr. Hullar puts it, Hearing aids are also balance aids.

Researchers from Finland tracked the lives of average citizens and found that people with hearing loss tend to fall. This was groundbreaking. We tend to think that both hearing loss and falling are merely casualties of old age. Now we know that there is a closer relationship, that loss of hearing causes some loss of balance.

In actuality, when you drink alcohol it affects every cell in your body . . . and it hits different parts of the body at different rates. Within the semicircular canals, alcohol builds up faster in the cupula than in the surrounding endolymph. And most importantly for the effect on balance alcohol is lighter than endolymph

Within a semicircular canal infused with alcohol, there is more alcohol in the cupula, making it float up regardless of how you move. Butand this is the critical butthe cupula is supposed to move in response to the changing flow of endolymph. It isnt supposed to float against gravity like a helium balloon!

Unbeknownst to you, your alcohol-soaked cupula is floating upward against gravity within the semicircular canal instead of responding to the endolymph current. That wayward cupula sends a messed-up signal to your brain that the body is moving. That message is constant for as long as the cupula is bent in the wrong direction, so the sensation of movement continues, even while you are standing still or lying down

This density difference, where the cupula is lighter than the surrounding endolymph, lasts about three to five hours. Then the amount of alcohol is equal in all parts of the inner ear, and the illusion of spinning stops

As alcohol leaves your body, it leaves the cupula more quickly. Since alcohol is lighter than endolymph, that means that the cupula becomes temporarily heavier than the surrounding fluid. Instead of rising up against gravity, the cupula presses downward, and the illusion of spinning starts all over again but this time in the opposite direction.

Whether they were walking on a balance beam, doing complex mathematics, or walking on a treadmill in front of a VR screen, young subjects and old subjects performed exactly the same. And then Dr. Franz and his team turned on the visual perturbation and saw age-related differences emerge that were not otherwise apparent. The old subjects could barely walk and stand straight at the same time, says Dr. Franz. It was a really rich response that we didn’t expect.

Why would this happen? Dr. Franz theorizes that it has to do with which portion of our complex balance system is dominant. Young adults prioritize the physical, proprioceptive/somatosensory feedback that pressure of body weight on their feet, that force information from under the feet to guide their motor responses. That’s the information they use to plan and execute balance from step to step. In aging, physical sensory systems are among the first things to go. The decline there is faster than is seen in some of the other sensory systems. Instead, older people have much more visual reliance. So even though you lose visual acuity as you get older, you actually have a greater reliance on vision as a reference for balance control. As Dr. Franz puts it, visual reliance goes through the roof. In that case, it’s easy to see why the visual perturbation (swaying hallway) would have such a dramatically different effect on young and old people

Of all the changes that happen as we get older, one of the most visible and individually frustrating is decline in walking speed and balance. We have three main calf muscles that power walking, and they do so while consuming very little oxygen, making it very economical power. In aging, we don’t use those muscles as much, for some reason. We compensate by using other muscles—quadriceps and hip extensor muscles—and those muscles aren’t architecturally designed to provide the same economical locomotion as the calf muscles. Scientists believe that’s one reason why older people take shorter steps and walk more slowly

The major part of Dr. Franz’s work involves trying to find the answer to why older adults walk slower, and why they consume more oxygen when they do so. The simplest explanation that all muscles get weaker with age doesn’t cover it. If you do strength training or are just generally physically fit, you don’t get a benefit that translates to more economical walking. You get stronger, sure, but you won’t change the way you move. One study from researchers in Norway found that seniors who were generally active, with a sports-heavy background, were no better off than sedentary seniors when it came to balance.

In the past year, Dr. Franz and his team used ultrasound imaging to look under the skin. Those three major calf muscles attach to the Achilles tendon. For many, many years, the Achilles has been thought of as one tendon, but it turns out that there are three separate tendon bundles, one from each of the three calf muscles. Those tendon bundles merge together and become the Achilles tendon. The researchers discovered that even though the three tendons are connected in this way, those bundles move independently and slide against one another in young adults. The same ultrasound imaging in eighty-year-olds doesn’t show any of that sliding movement. And researchers have correlated the sliding behavior with the mechanical output of the calf muscle, so more sliding means better power output from those muscles during walking. It sounds like this sliding motion is a good thing, but the discovery is so new that no one really knows what it all means

One general observation is that older adults tend to coactivate their muscles more for balance control and for gait, perhaps to compensate for feeling unstable. This means that, instead of specifically activating just that one leg-move muscle module, older people involve more muscles. So the muscles are overly active, sometimes even fighting each other, but they get the movement done. The cost, however, is that movement takes more energy. Again, we see that the gas mileage of muscle use for older people isn’t great.

If gas mileage were the only problem, then these coactivating muscles wouldn’t be such a consideration. But they also make us unstable and more likely to fall.