When your inner ear is damaged suddenly and severely due to a viral infection or trauma, there are a lot of miserable symptoms that make life difficult: the room spins, nausea can be overwhelming, and you can bump walls when walking or even fall over. Once your balance starts to return in a few days you might notice a new and more long-lasting symptom—trouble finding your way. Inner ear damage interferes with mapping skills, and this can be long-lasting, although it gradually improves over months.
How does a normal person keep track of their orientation in space? The inner ears are critical. Your brain has the ability to keep track of your movements through our three-dimensional world. It combines what you see around you and also remembers which directions your head moves at the same time. This allows you to estimate how far and in what direction you have traveled and to retrace your steps quite precisely. For example, if you go down your street to the next corner and make a right turn, you will see some familiar landmarks and you will understand where you are by what you see. Without your noticing, your brain will also have kept track of each of your head movements—turning when you leave your house, turning right at the corner—and provided those align with what your eyes see, you will “know” where you are in space. Everything will look familiar and you will feel oriented.
When you have a sudden loss of inner ear function, all of this changes. Because I have experienced a total loss of inner ear function in an ear, I was able to see what happens when what you see does not match where the inner ear tells the brain you are.
For example, I entered a perfectly familiar indoor mall with friends. We went to a large rectangular fountain near the entry, and there we split up to shop in different stores and agreed to meet at the fountain in an hour. I browsed along the well-known storefronts and then began making my way back to the entrance. As I was getting close to where I thought the entrance should be, I found a large fountain. It looked remarkably similar to the one I had started at, but it was oriented wrong. It looked like an east-west fountain instead of a north-south one. There was an entrance near it, but it was also wrong, about 90 degrees off from where the actual entrance should be. This was so confusing that I went to the wall where the entrance felt like it should have been, but it was just a blank wall. Luckily, my friends showed up at the fountain shortly after that and assured me this was the same exact fountain, but even after that it still looked like it was exactly sideways.
After several similar experiences, it became clear that there was a slight error in my brain’s ability to keep track of head turns. This is not noticeable as you move about on short excursions in a familiar environment, but as the number of turns on your track increases, these little errors begin to add up to a big error in your calculated position in space. Before my injury, I was able to park anywhere in a large lot and go to a store and then go back to my car without the slightest conscious thought. After the injury, I must be very careful to notice waypoints (like those helpful pictorial signs) as I leave. I always try to look back at my car as I get to the storefront to make sure I know what the correct direction back looks like. Vision now must substitute for the miscalculated trajectory my inner ear sends to the brain.
Why is this? When an inner ear is not functioning, there is some improvement over time as the other ear is able to make up for some of the lost function. However, this is not 100%. When I turn toward my good right ear, the ear sends the brain perfect information about the turn. When I turn toward the bad ear, only part of this information is sent because only the good ear can send it—the bad ear is dead. It’s a guess by my good ear, never as large as the correct number would be. So my brain gradually acquires a bias toward the good ear. For example, for a good right ear and a dead left one, even if the path involves the same number of right and left turns, your brain will begin to think you are steadily drifting right. The more turns you make in a single path, the worse the error becomes. If you then try to retrace your steps, you can head off in a completely wrong direction.
Just as you can become visually dependent for balance after an inner ear disease, it is important to know that you will also be visually dependent for orientation in space. It’s not a good idea to wander off into the woods without a friend after such injuries. Unless waypoints are very clear (like street signs or buildings you know well) it is too easy to drift off the correct path. Using the map function on your phone may be your best bet.