Why Vestibular Rehabilitation Works
In order to understand how Vestibular Rehabilitation works and the underlying corrective mechanisms, it is important to remember that the primary role of the vestibular system is to tell the brain where the head is in space. Quite simply, the vestibular system is our internal reference telling the brain how our head is orientated - up, down, tilt, etc. The visual and somatosensory (touch, pressure, pain) systems, on the other hand, are external references, providing our brain with information about the movement and stability of the world around us. Working together and when the systems agree, it is the integration of these sensory modalities that provides us with normal equilibrium.
When there is a conflict between internal and external references, the result is the brain's inaccurate perception or hallucination of motion, or vertigo (dizziness). An example of this occurring in everyday life is the feeling of moving forward when stopped at a traffic light, when a larger vehicle in your peripheral vision has rolled backward. There was simply a conflict between the three sensory modalities. The input from the motion detector aspect of the visual system overrode the input from the vestibular and somatosensory systems creating the hallucination or perception of motion.
Another way to look at a conflict in the balance system is to think of yourself as a car with a front-end alignment problem. If you take your hands off the wheel, if you are distracted, or if the environment is challenging, you can find yourself drifting into another lane. In a sense, this is the "dizziness" you may experience with a balance disorder. Hitting the berm or getting a horn from someone next to you is the signal you are going off-kilter. It is the symptoms of dizziness - the possible nausea, visual sensitivity, motion intolerance, and/or feeling of unsteadiness that you may feel with a balance disorder. It can last for seconds, minutes, hours, days, or daily. The first thing you will want to do is avoid the sensation - I would think the same. If something makes you feel sick, you're first inclination is to stop the movement. You may also be given vestibular suppressants to reduce the symptoms - over 70% of all patients going to the PCP for dizziness are given Meclizine. The problem with both these issues is that in most cases (not all), this is the exact opposite of what you should do. Have you ever wondered how a figure skater spins or a combat pilot flies a jet - they challenge to the point of "dizziness" or "disorientation" and then recover. They do it in a dose like manner - just like taking a pill for arthritis pain. Through repetition, practice, and mental training most are able to reduce the symptoms and even eliminate the problem. This is what needs to be done with most balance disorders but frankly is not done.
There Are Three Accepted Models To Explain Why Therapy Works:
Adaptation: The central vestibular system (brainstem) and brain learns to adapt to the imbalanced signal coming in from the impaired peripheral vestibular sensory receptors. The role of the vestibulo-ocular reflex (ear-eye reflex) is to keep the eyes focused on a target during head movement. If the incoming signal from the two internal head movement sensors (canals and otolith organ of your ear) is not in synchrony, the result is a sense of "after-motion" with head movement (you feel dizzy/off balance). A primary component of the balance system adversely affected by the imbalance from the two peripheral vestibular mechanisms is the vestibulo-ocular reflex (keeps eyes steady). Gaze stabilization exercises work to "return" the vestiblo-ocular reflex to eliminate the retinal slippage (blurred vision) and the patient's perception of this "after motion." Another easily understood example is that of the two propeller airplane with one propeller operating at only half the Rpm's of the other. There is no way to increase the damaged or reduced propeller's output, so the onboard computer is programmed to accept or adapt to the imbalanced signal and maintain the plane's trajectory and course.
Substitution: The role of compensatory shift when one or more sensory systems is lost or damaged is well known. The visually impaired individual does not develop better acuity, nor does the deafened individual gain better vision. They simply utilize their remaining senses more efficiently. The redundancy of multiple sensory inputs allows the fully intact individual to waste much of the input. So, for the individual who has lost vestibular function, dependency on the remaining equilibrium sensory components, e.g. vestibulo-spinal, cervico-spinal and visual inputs, must be made trustworthy.
Habituation: As Dr. Tim Hains explains, " If one exposes oneself to something over and over, one may get "used to it". In physiology, this is called habituation, and it works for dizziness too. Examples of this approach are the "Norre" exercises and the "Kitchen sink" approach to dizziness. The main problem with this approach is that it takes a long time and it is difficult to tolerate the repetitive motion needed to make an impact."