You probably wonder how you are able to stand and walk properly even with your eyes closed. Do you know that the system that controls body stability or sense of balance is more than just the bone, muscle and nerve system? Another system known as vestibular system provides information about position that allows rapid movement as response to forces that hits the body. This is why it is important to get health screening as to ensure all the body systems that control the body balance and movement are in good shape.
The vestibular system is a complex sensory system that is located within the inner ear. This area is known as vestibular labyrinth. The vestibular system consists of semicircular canals and two otolith organs. Semicircular canals are the 3 tubes which detect different types of movement such as nodding up and down, shaking side to side or tilting left and right. The two otolith organs detect linear acceleration, gravitational force and tilting movement. The vestibular nerve transmits information from these vestibular organs to the brainstem which then relay to other parts of the central nervous system. The information will then be used by the brain, particularly the cerebellum and cerebral cortex to coordinate movement. The vestibular system senses the orientation of our body relative to gravity and thus helps us maintain balance.
To test the vestibular system, there are several ways of evaluating the vestibular function. There is no direct way to measure inner ear function. Thus, tests to check for vestibular systems emphasize on using information from specific reflex in the brain that links inner ear function and eye movements. Eyes will become the window to the inner ear function.
There are many types of vestibular tests. Audiologists will choose which is needed based on the symptoms affected by the vestibular system. Among of the common tests are:
- Video-nystagmography (VNG)- a test that uses goggles to track eye movement using video recording or electrodes. This test will look for presence of nystagmus, which is a specific eye movement that related the eyes and inner ear together.
- Vestibular evoked myogenic potentials (VEMP)- a test that uses electrodes and sound stimulus to measure response that travels from neck muscles to the inner ear. This test helps to test otolith organs. 3 electrodes are attached: one on the forehead, one to the neck muscle and one on the collarbone.
- Caloric test- in this test, each ear will be irrigated or flushed out with warm and cool water in turn for 30 seconds. This test can measure the function of the semicircular canals. Caloric test may be performed while lying on the couch while wearing VNG goggles to evaluate eye movements and nystagmus.
Both tests of ENG & VNG often need patients to perform simple tasks such as locking eyes on target and following the target as it changes direction, moving head and body in different positions and having warm or cool air or water placed in the ear canal. Rotary chair test with VNG sometimes is done with the chair moving gently in a certain motion. In general, vestibular testing may take 2 hours. The tests mentioned above are only among the many vestibular tests. Do speak to your doctor or audiologist for further information regarding the test.
What next to be done after completing the test will depend on the result. If results seem normal, there should be no problem. However, if results seem off, there might be something wrong with the vestibular system. This will then be proceeded with other tests such as blood tests or imaging tests such as MRI or CT-scan to get a clear picture of what has been the cause for the abnormality.
There are many conditions that can affect the vestibular system. Among the common ones is benign paroxysmal positional vertigo (BPPV). BPPV is often triggered by quick changes in position and is caused by the loose calcium carbonate crystals that are dislodged from the normal part of the vestibular labyrinth. People with BPPV typically complain of a brief period of dizziness, nausea, vomiting and loss of balance. Another common disease affected by the vestibular system is Meniere’s disease. Meniere’s disease is caused by fluid buildup in the vestibular labyrinth. Meniere’s starts with a single symptom of low-tone ringing to the ear and progresses to something worse. It often causes severe dizziness and even hearing loss.
It can be concluded that the vestibular system, which has its organs mainly in the inner part of the ear, plays a significant role in coordinating movement and balance. There are several tests that can be done to evaluate the vestibular. Vestibular testing not only helps to detect if symptoms arise from the inner ear or relating to the brain, but also help healthcare providers to rule out an inner ear condition such as injuries or medications that might be also causing symptoms of balance disorder.
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