Unilateral and Bilateral Vestibular Loss
Unilateral and Bilateral Vestibular Losses occur due to partial or completely impaired function of one (unilateral) or both (bilateral) peripheral vestibular or central vestibulocerebellar systems. The vestibular system has several roles. One is to stabilize your vision while your head is in motion. The other is to sense head movement and communicate this to your brain, therefore assisting you in maintaining your balance. When dysfunction occurs at the vestibular system level in this processing loop, it is called “peripheral”, and when the dysfunction is within the brain or brainstem, it is called “central”. A well-trained vestibular provider using the right equipment is able to determine the origin of the problem based on exam findings and diagnostic testing. Vestibular rehab, when done properly and targeted to the origin of the problem, is helpful in the event of either central or peripheral disorders; however, progress is more gradual in the treatment of a central impairment and will vary according to unilateral vs bilateral involvement.
Unilateral vestibular loss may occur for a variety of reasons, including vestibular neuritis and labyrinthitis as 2 examples. These are infections, often viral, which attack the nerves going to either the vestibular system, or both the vestibular system and the hearing center, the cochlea. Often these infections originate from another site, such as a sinus infection, GI infection, or even the shingles or cold sore virus. Sometimes, the inner ear is the primary site of the infection. Viruses of the inner ear may cause extreme vertigo, at times with nausea and vomiting, persisting hours up to a day or more. If caught early, medications may be helpful in reducing inflammation associated with the infection. While the infection itself passes within days, there can be a more long-term “scarring” of the vestibular system, which can cause symptoms such as bouncing or blurred vision with head movement and instability of gait, or dizziness with rapid head turns. Most people will recover fully without any intervention, but those who do not fully recover on their own, may require vestibular rehab to accelerate the recovery process.
Other causes of unilateral vestibular loss or hypofunction include loss of blood flow from a labyrinthine artery stroke, or Meniere’s Disease. Meniere’s Diseases is an autoimmune condition, which results in over-accumulation of sodium and fluid in the inner ear. Episodes of Meniere’s may present very similar to an episode of vestibular neuritis or labyrinthitis. Meniere’s Disease does not currently have a known cure, but by avoiding triggers, most people with Meniere’s are able to manage their episodes. Triggers of Meniere’s Disease include caffeine, alcohol, tobacco, stress and sodium. Meniere’s Disease may initially cause a unilateral vestibular loss, but 10-20% of patients with Meniere’s will develop it bilaterally.
Most patients with a unilateral vestibular loss can largely recover their balance processes with gaze-stabilization exercises and balance training. Typically, gaze-stabilization exercises do not need to be performed forever in someone with a unilateral loss, as adaptation occurs. Most patients with a unilateral loss reach maximum benefit from vestibular rehab within 6 weeks of onset of therapy.
Bilateral vestibular loss may occur due to sequential episodes of any of the above-mentioned conditions. Additionally, bilateral vestibular loss may be a side effect of ototoxic medications, such as gentamicin or chemotherapy. At times, bilateral vestibular loss may be congenital. This is more common in those born with congenital hearing loss. For most people with bilateral vestibular loss, the cause is idiopathic, meaning that there is no identifiable cause. While rehab for a unilateral loss may focus more on adaptation (because there is one remaining strong vestibular system), those who have had a bilateral loss will depend more on compensation and substitution. This means that patients with a bilateral loss will compensate with their two remaining balance systems: vision and proprioception. By tapping into these sensory systems, most with a bilateral loss will see maximum gains from vestibular rehab within 12 weeks. It is suggested that patients with a bilateral loss keep up with their exercises throughout their life, in order to prevent decompensation.
In order to properly diagnose a unilateral or bilateral vestibular loss, the vestibular provider may suggest diagnostic testing such as VNG (videonystagmography), vHIT (video head impulse testing) and CDP (computerized dynamic posturography). Once the provider determines an appropriate diagnosis, the patient can initiate exercises which will be specific to the patient, their diagnosis and their functional limitations. Vestibular rehab can significantly improve outcomes for patients diagnosed with either a unilateral or bilateral vestibular loss.
Unilateral vestibular loss may occur for a variety of reasons, including vestibular neuritis and labyrinthitis as 2 examples. These are infections, often viral, which attack the nerves going to either the vestibular system, or both the vestibular system and the hearing center, the cochlea. Often these infections originate from another site, such as a sinus infection, GI infection, or even the shingles or cold sore virus. Sometimes, the inner ear is the primary site of the infection. Viruses of the inner ear may cause extreme vertigo, at times with nausea and vomiting, persisting hours up to a day or more. If caught early, medications may be helpful in reducing inflammation associated with the infection. While the infection itself passes within days, there can be a more long-term “scarring” of the vestibular system, which can cause symptoms such as bouncing or blurred vision with head movement and instability of gait, or dizziness with rapid head turns. Most people will recover fully without any intervention, but those who do not fully recover on their own, may require vestibular rehab to accelerate the recovery process.
Other causes of unilateral vestibular loss or hypofunction include loss of blood flow from a labyrinthine artery stroke, or Meniere’s Disease. Meniere’s Diseases is an autoimmune condition, which results in over-accumulation of sodium and fluid in the inner ear. Episodes of Meniere’s may present very similar to an episode of vestibular neuritis or labyrinthitis. Meniere’s Disease does not currently have a known cure, but by avoiding triggers, most people with Meniere’s are able to manage their episodes. Triggers of Meniere’s Disease include caffeine, alcohol, tobacco, stress and sodium. Meniere’s Disease may initially cause a unilateral vestibular loss, but 10-20% of patients with Meniere’s will develop it bilaterally.
Most patients with a unilateral vestibular loss can largely recover their balance processes with gaze-stabilization exercises and balance training. Typically, gaze-stabilization exercises do not need to be performed forever in someone with a unilateral loss, as adaptation occurs. Most patients with a unilateral loss reach maximum benefit from vestibular rehab within 6 weeks of onset of therapy.
Bilateral vestibular loss may occur due to sequential episodes of any of the above-mentioned conditions. Additionally, bilateral vestibular loss may be a side effect of ototoxic medications, such as gentamicin or chemotherapy. At times, bilateral vestibular loss may be congenital. This is more common in those born with congenital hearing loss. For most people with bilateral vestibular loss, the cause is idiopathic, meaning that there is no identifiable cause. While rehab for a unilateral loss may focus more on adaptation (because there is one remaining strong vestibular system), those who have had a bilateral loss will depend more on compensation and substitution. This means that patients with a bilateral loss will compensate with their two remaining balance systems: vision and proprioception. By tapping into these sensory systems, most with a bilateral loss will see maximum gains from vestibular rehab within 12 weeks. It is suggested that patients with a bilateral loss keep up with their exercises throughout their life, in order to prevent decompensation.
In order to properly diagnose a unilateral or bilateral vestibular loss, the vestibular provider may suggest diagnostic testing such as VNG (videonystagmography), vHIT (video head impulse testing) and CDP (computerized dynamic posturography). Once the provider determines an appropriate diagnosis, the patient can initiate exercises which will be specific to the patient, their diagnosis and their functional limitations. Vestibular rehab can significantly improve outcomes for patients diagnosed with either a unilateral or bilateral vestibular loss.