Aging and multisensory imbalance

In order to sense motion and have normal balance, your body uses three overlapping systems, called the balance triad.  The inner ears are critical to sensing motion;  the eyes and depth perception help locate you in space, and your body, arms and legs feel the floor and your surroundings to help orient you.  If any one of these three systems is impaired, you will start to feel off balance.  If two out of three of these systems don’t work properly, your risk of falling will greatly increase, and if all three are impaired, you might not be able to walk at all.  Multisensory imbalance occurs when two or three of these systems are not functioning fully.  As we age we are likely to accumulate small problems in each of these areas, and that eventually results in poor balance.  Most older people accordingly suffer from some degree of multisensory imbalance.   

The key symptom is feeling off balance or dizzy when standing or walking, but not as much when sitting or lying down.  You may feel even more off-balance when walking in dim light or darkness.  Using a grocery store cart while shopping greatly helps.  Just holding onto your spouse’s arm while walking can make you feel more steady.  There can be a sense of dizziness in the head, typically a floating, disoriented feeling as if you are no longer connected to gravity.  You are much more likely to fall when you have this condition.

When one system in the balance triad becomes damaged, you learn to boost function in the remaining two systems and you may even become dependent on one of these backup systems for most of your balance. The inner ears are the most important system in the balance triad and provide an internalized framework for perceiving the movement of the head and its position in space. Because the inner ears are already the most important frame of reference for balance, their function cannot be easily boosted if there is damage to one of the other two balance systems.  For this reason vision turns out to be  the most important back-up balance system, and the next most important is feeling the environment through the limbs. 

If you have positional vertigo or any other condition that interferes with the inner ear balance system, you may notice that you need your eyes more for balance when the vertigo is flaring up.  This is called visual dependence.  You will feel increased dizziness and poorer balance when in the dark or in dim lighting, or when you close your eyes.  It can also create strange new dizziness problems, like intense feelings that you are actually moving when watching tilting and panning scenes in the movies or IMAX  theaters.  Seeing nearby cars move when you are stopped at a light might make you feel that your car is suddenly moving.  Walking in a mall or grocery store with lots of movement at eye level can make you feel unpleasantly dizzy.

Not everyone has perfect, three-dimensional vision to act as a balance back-up.  If one eye has poorer vision because of cataracts, glaucoma, or another injury, then depth perception is impaired and vision cannot be used as effectively for balance.  Everyone has some degree of imbalance if their eyes are closed or they are in complete darkness.  Even using bifocals or progressive lenses can interfere with balance, because it is harder to focus on the ground when these are used. Under any of these circumstances, you will have to use touch to make up for your imbalance.  You can feel the ground  through your feet, and tell whether it is flat or slanted, rough or slippery.  By reaching out with the hands, you can touch your surroundings and can tell where you are in space.  This sense is called proprioception, and it is the final balance system back-up in the triad.

People who have visual impairments can easily develop proprioceptive dependence.  Our feet are in constant contact with the ground when we walk, so that can’t be boosted very much.  Instead, we begin to rely more on input from our hands and arms.  A blind person often uses a cane to tap the ground, giving more input to the hands about the ground ahead of them.  When you walk in the pitch-dark, you’ll often throw your hands out ahead of you and feel for furniture when walking.  If the ground is uneven, like on a rough boulder field while hiking, you might choose to use trekking poles in both hands and notice that it greatly improves your stability. 

Aging tends to damage proprioception and touch sensations in the legs and feet, a problem called peripheral neuropathy.  You can test this by touching something cold to the back of your hand (like a spoon) and then touching it to the top of your foot.  If you can’t feel the cold as intensely, you may have neuropathy.  This means that the feedback to your balance system from your feet may not work as well as it should.  If the feet can’t be trusted to give enough information about balance, the hands and arms can help.  People with this problem like to walk holding a companion’s arm, or they may touch the walls or furniture while walking.  The first step in treatment is to use trekking poles while walking, which can greatly relieve the symptom.  A cane is often used, but you get more balance feedback if you use both hands rather than just one, so hiking poles are better.  Using a walker or pushing a grocery cart can help as neuropathy worsens. 

Our next post will answer questions from our readers.

Published by Vertigone

I translate the medical world of dizziness for non-medical people

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