These words are never good to hear… especially when they come from the back seat of your car as you drive down the highway. With the summer season approaching, this scenario will play out in more than just a few minivans as they migrate down the road to family vacation spots.
Motion sickness is a relatively common complaint that results from sensory mismatch, a situation when the brain receives conflicting information about where we are in space. Our ability to feel “oriented” is dependant on our brain’s ability to process simultaneous messages from our inner ear, our vision and the muscles and joints in our body – especially our neck. Our inner ear detects changes in head movement and tells our brain where our head is. Our muscles and joints tell our brain where our body is, and our vision lets us know where we are in relationship to the external world.
These different signals are all sent to a common processor in our brain, where ideally, the three messages complement each other and our brain can cross-triangulate our position in space like a GPS, making us feel oriented. The bottom line is that our brain’s ability to know where we are is only as good as the quality and amount of the information it receives from these systems.
When you read a book in the back seat of a moving car, our spine and inner ear detect changes in our speed and direction and tell our brain that we are moving, but our eyes are sending a conflicting message that says we are sitting still and reading a book. Usually, our brain is able to recognize that there is a 2 to 1 vote occurring and resolves the sensory mismatch by putting more weight on what the ears and spine have to say and will rely less on our visions in terms of knowing where we are in space. In other words, our brain can compensate as long as the remaining two systems are functioning well.
Problems arise when one of the three systems is either signaling too much, or too little, or if the central processor in our brain isn’t working well. Our brain has a check and balance system and when either our visual system, inner ear or spine aren’t working properly, most people compensate by learning to rely more on the information they receive from the remaining two systems. This is a good thing, but sometimes with chronic dysfunction, our brain may learn to depend too much on one of the two remaining functional systems and one becomes overly dominant. The result is that the information our brain receives becomes skewed and instead of relying equally among the three systems, too much emphasis is placed on the one that has now become overly dominant. It can be like having three back seat drivers giving you directions, but one is asleep, one is whispering and one is yelling! For example, some people I have consulted with are so visually dependant that just looking at a merry-go-round makes them feel dizzy and nauseous.
It should be apparent that the cause of motion sickness can vary considerably among people. Parts of our nervous system develop at different rates and some people go through life with asymmetry of brain function and processing ability. Fatigue or excessive stimulation may also limit the brain’s ability to compensate in an otherwise healthy person. Many common antibiotics and medications are ototoxic and can damage portions of the inner ear, impairing our ability to stabilize our eyes when we move our head. People with this condition sometimes feel like the world bobs up and down as they walk or the words on a page tend to vibrate when they read. Head and neck injuries can impair the ability of the muscles and joints to function properly and tell the brain how we are moving. Neck injuries tend to contribute more to balance problems than back injuries because the muscles and joints in our neck have more motion sensors in them. This makes sense given the fact that when we stand upright our neck is essentially at the top of the flagpole and needs to sense body sway more than our lower body.
Many people who suffer from motion sickness can be helped with proper treatment. The key to treatment success lies in uncovering the underlying problem a person has and developing a treatment plan that is specific to that particular individual. Promoting an enriched sensory experience that complements a person’s impairment can often result in amazing improvement. One person may do best with a specific form of eye exercises, while the next will do best with having their spine manipulated in a certain way or with vestibular rehabilitation such as spinning to one side or balancing activity that emphasizes one side. Successful treatment can often mean the difference between having to stay home and the freedom to go on a cruise or simply read a good book in the back seat of a car.