Bilateral vestibular hypofunction
Bilateral vestibular hypofunction (BVH) refers to a decrease in vestibular function on both left and right sides. Most cases of BVH have no obvious cause, and are therefore referred to as “idiopathic”. In some cases, the vestibular function has been affected by medications, auto-immune disorders, meningitis, chronic inflammatory polyneuropathy, or neurofibromatosis.
As expected, this condition results in decreased balance and decreased ability to fixate the gaze on a target whilst moving the head (oscillopsia). In particular, people suffering BVH will find it difficult to balance whilst in the dark, since they are unable to rely on the sense of vision.
BVH can lead to significant changes in gait, an increased falls risk, difficulty driving and a sense of disequilibrium. Often these symptoms will cause a lack of physical conditioning, or even social withdrawal, due to lack of participation and a fear of falling.
It is likely that the older and more incapable patient will be more at risk of falling, due to the decreased ability to compensate for the vestibular loss.
Evidence exists that specific exercise for people with BVH can improve visual stability during head movements, as well as postural stability during walking.
Vestibular rehabilitation is aimed at teaching the brain to better recruit the sense of vision and proprioception to compensate for the lack of vestibular input. Rehabilitation may also include gaze stability exercises whereby the eyes maintain focus on a target whilst the body or head moves, however, the benefits of these exercises is limited due to the lack of function on both sides. Nevertheless, compensatory eye movements may be helpful in improving coping mechanisms, and improvements are always possible through graduated balance exercises, with challenging environments which force the brain to adapt.
Despite the possibility of improved function through exercise and rehab, it is likely that a person suffering BVH will continue to have ongoing symptoms.
