Bilateral vestibular loss implies that there has been reduced function of both inner ear (vestibular) nerves. Typical symptoms include oscillopsia (includes blurring of vision to rapid back-and-forth movement of vision), especially with head motion, while riding in a car, or walking, and difficulty with balance in darkness or when walking on compliant (uneven) surfaces, such as grass. Vertigo (false sense of motion) is typically not present.
Bilateral vestibular loss is often idiopathic (we don't know why it occurred). However, there are several known causes, including:
Toxicity from medications, such as gentamicin
Bilateral Vestibular Neuritis
Vestibular Schwannoma (often bilateral in Neurofibromatosis II)
Autoimmune inner ear disease
Bilateral vestibular loss is best diagnosed by vestibular function testing, including specifically the caloric portion of the Videonystagmogram (VNG) test, the Rotary Chair, and Vestibular Evoked Myogenic Potential (VEMP). Rotary chair is the gold standard in confirming the diagnosis of bilateral vestibular loss, as both the caloric test and the VEMP may give false positive results for bilateral vestibular loss.
Below is the result of a caloric test from a patient with bilateral vestibular loss. Note that there are no nystagmus responses elicited from either side using cool or warm air.
Below is the result of a rotary chair test from a patient with bilateral vestibular loss. Note that the VOR gain is extremely low.
Below is the result of a VEMP test from a patient with bilateral vestibular loss. No waveform was elicited from either inferior division of the vestibular nerve.
Treatment of bilateral vestibular loss involved a special type of Physical Therapy known as Vestibular Rehabilitation Therapy (VRT). The type of VRT employed for bilateral vestibular hypofunction is quite different from the VRT used for unilateral vestibular hypofunction and improvement for those with bilateral vestibular loss is typically more slow and incomplete compared with unilateral vestibular loss. Patients with bilateral vestibular loss should avoid taking any medications that might reduce vestibular system function, including meclizine (Antivert), diazepam (Valium) or other benzodiazepine medications, and promethazine (Phenergan).
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