Bilateral vestibulopathy: clinical, diagnostic, and genetic considerations.

Bilateral vestibulopathy is a rare, but important cause of imbalance that is underrecognized and not well understood. Clinically heterogeneous, it is variably associated with recurrent vertigo, hearing loss, migraine, peripheral neuropathy, or cerebellar degeneration. In about half of all patients with bilateral vestibulopathy, no cause can be identified. There have been several reports of familial bilateral vestibulopathy, suggesting genetic predisposition. The identification of genetic defects underlying hereditary deafness syndromes has greatly advanced the understanding of the functional components and the development of cochlea. In contrast, the progress in bilateral vestibulopathy has been slow, likely hampered by the difficulty in diagnosis outside of academic centers and a lack of animal models that recapitulate the progressive clinical features that are not apparent from birth. It is reasonable to anticipate that there will be an equally large number of genetic disorders underlying bilateral vestibulopathy as in deafness. Understanding the pathophysiology of bilateral vestibulopathy may suggest possible causes for the gradual decline in vestibular function that occurs with normal aging. Furthermore, the study of bilateral vestibulopathy may shed light on the pathophysiology of more common vestibular syndromes such as benign recurrent vertigo and vestibular migraine.