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Understanding the Vestibular System and Dizziness

By April 19, 2021Balance, Physical Therapy

Balance is a complex system made up of three major components: sensation coming from the joints and tissues of our bodies, visual input about our environment, and an “inner sense of balance” that comes from our vestibular system. Feeling unsteady, off balance, dizzy, or having trouble keeping steady in the dark can indicate a vestibular problem. 

The vestibular system is made up of two major divisions: peripheral and central. The peripheral vestibular system consists of a set of structures in the inner ear which detect changes in the position of the head. The central vestibular system is made up of parts of the brain responsible for processing input from the peripheral system. Basically, information about movement of the head travels from structures of the inner ear to the brain, and the vestibular centers of the brain are responsible for making sense of that information. The brain and inner ear are connected by the vestibular nerve (the eighth cranial nerve), which is considered a part of the vestibular system once it passes through the skull into the inner ear. 

Image credit: BC Balance and Dizziness

The peripheral vestibular system in the inner ear consists of a series of “tubes” (called semicircular canals, labeled “semicircular ducts” in the picture above) that are made of bone and filled with a thick fluid called endolymph. Inside the endolymph float small calcium carbonate crystals called otoconia. When you turn your head, the otoconia change position in the canal and brush up against small receptors that send information along the vestibular nerve to the brain for processing. Think about it like snow in a snow globe – when the snow globe is moved, the small pieces of snow float through the fluid inside, and when the snow globe is still, they settle back down to the bottom. 

A common condition called benign paroxysmal positional vertigo (BPPV) happens when some of the small crystals – otoconia – are displaced and move into the wrong semicircular canal. This sends the brain the wrong signals about where your head is moving, resulting in a spinning sensation called vertigo. This unpleasant sensation most frequently occurs for people when rolling over in bed, tilting their head back in the shower, or bending down to pick something up from the floor. If this sounds like a problem you have experienced, a thorough vestibular evaluation at Hands On Physical Therapy can determine if BPPV is indeed what you’re experiencing. 

The list of other possible vestibular disorders someone can experience is very long since the system is so complex. Types of vestibular dysfunction can usually be classified as either peripheral or central, depending on which major part of the system is affected. BPPV is considered a peripheral vestibular problem since it affects the structures of the inner ear, but another common peripheral problem includes unilateral vestibular hypofunction (UVH). In this case, hypofunction refers to “decreased” function of the vestibular nerve, and unilateral refers to the fact that it is only on one side.  This can happen from  infection or damage to the nerve. UVH typically doesn’t leave people feeling the “spinning” sensation of positional vertigo. Usually, people with UVH describe feeling off balance, unsteady, or like they are on a boat. 

Regardless of the type of vestibular dysfunction, a thorough vestibular exam by an experienced physical therapist is crucial to determine what parts of the vestibular system are involved. This usually involves looking at the coordination of eye and head movements, balance, and positional testing with infrared goggles. At Hands On Physical Therapy, we now have a set of infrared goggles which we can use to enhance testing for vestibular dysfunction, giving us a more in depth look at eye movements during positional vertigo testing. Stay tuned for more information about how infrared goggles work, and how we can use them to assess your dizziness. 

If you are interested in learning more about your balance, Hands On Physical Therapy offers a balance screening clinic: click here to receive more information! 

Stay tuned for more information to come regarding additional aspects of balance assessment and retraining with a Physical Therapist at Hands On Physical Therapy.


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