Vestibular Hypofunction

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Answer

Vestibular hypofunction refers to a partial or complete deficit in the function of either the peripheral or central vestibular system. The peripheral vestibular system starts at the point where the nerve exits the brainstem and extends all the way into the ear, directly connecting to the system. On the other hand, the central vestibular system is located at the entrance of the nerve into the brainstem and includes all the connections from there to the rest of the brain and eyes.

The prevalence of unilateral or bilateral vestibular hypofunction in the general professional population is estimated to be around 6.7%. Notably, unilateral hypofunction is more common than bilateral hypofunction. Among symptomatic older adults, over 25% are expected to have some form of hypofunction, and this prevalence tends to increase with age due to the degeneration of the vestibular system over time. The horizontal and superior semicircular canals are the most commonly affected areas.

Some common causes of vestibular hypofunction include:

• Vestibular Neuritis: The most common cause of vestibular hypofunction and involves damage to the vestibular nerve. It can occur when the nerve is still connected to the cochlear piece of the nerve, or it can happen when the nerve splits from the cochlear piece, affecting only the part that supplies the vestibular system.
• Labyrinthitis: In this condition, the entire vestibular system is affected due to a viral infection or other factors.
• Post-Surgical Complications: Vestibular hypofunction can also result from various types of surgeries, including ear surgeries, where damage may occur to the vestibular system.
• Trauma: Any direct impact to the vestibular system, such as injuries causing harm to the bony casing or the system itself, can lead to vestibular hypofunction. Vestibular hypofunction is commonly observed in concussions, head injuries, and other traumatic events that can cause damage to the vestibular system.
• Toxicity is another known cause of vestibular hypofunction, particularly associated with intravenous gentamicin. Gentamicin is an antibiotic that can be toxic to the vestibular system, and its usage can often lead to bilateral loss of vestibular function.

Surprisingly, in about 50% of cases, the exact cause of vestibular hypofunction remains unknown. This emphasizes the need for further research to understand better and manage such cases of vestibular hypofunction with unknown causes.

This Ask the Expert is an edited excerpt from the course Vestibular Hypofunction by Tonya Fuller, MSPT