According to Medicine Net, vestibular refers to "a structure that is a vestibule (entrance), such as the vestibule of the ear" as well as "the body's system for maintaining equilibrium." At the most basic level, vestibular hypofunction refers to a condition in which a person experiences disorientation or dizziness due to issues in the ear.
Spatial disorientation is a common symptom of vestibular hypofunction and will likely become worse with movement of the head. A sufferer may have difficulty with balance, trouble moving and walking in the dark, and a sense that they are "jiggling" when they walk. Driving on an uneven road or performing other tasks that create "high-frequency oscillations" can be difficult. Individuals with vestibular hypofunction may have trouble seeing at times, experience vertigo and have trouble maintaining an appropriate posture.
Unilateral and Bilateral
Unilateral vestibular hypofunction refers to a problem with the vestibular nuclei in one ear only. As the firing patterns fluctuate for the neurons in that ear, the brain interprets the firing as a head rotation, thus causing balance issues and instability. Bilateral hypofunction affects both ears and may cause more significant symptoms, such as vertigo. Some people begin by having bilateral hypofunction while others develop bilateral issues from unilateral problems.
According to the Journal of American Physical Therapy Associates, unilateral vestibular hypofunction often is caused by "vestibular neuronitis, which is commonly caused by the herpes simplex virus." Other causes include Meniere disease, "vestibular schwannoma on the eighth cranial nerve," and brain injury.
Bilateral vestibular hypofunction is most commonly caused by aminoglycoside antibiotics, which can damage vestibular hair cells. Other causes include BVH meningitis, head trauma, tumours and repeated problems with unilateral vestibular hypofunction. Per Sight Street, bilateral hypofunction can also be caused by "otosclerosis, radiation treatment and idiopathic degeneration."
Numerous options exist for diagnosing vestibular hypofunction. A doctor may examine a patient's eyes by asking him to perform a sight test while moving. A doctor may also ask a patient to "thrust" his head repeatedly, turn his head quickly to the side, or move his head at specific angles and then quickly lay down. A warm or cold substance (such as water) may be introduced into the ear canal to see what impact the change in temperature has on the condition. A patient suspected of having bilateral hypofunction may be put in a rotating chair and monitored as he turns to determine what signals his body sends relative to the norm for such an activity.
If the condition is caused by an underlying issue, such as a tumour, the first step is to appropriately treat the base condition. When the condition is not connected to such a cause, rehabilitation is possible using some basic therapies. These may include adaptation exercises, ways of repositioning the body and exercises designed to improve balance, movement and muscle strength.