Bilateral vestibulopathy

Bilateral vestibulopathy is characterized by postural imbalance and unsteadiness of gait that worsens in darkness and on uneven ground and head or body movement-induced oscillopsia in some patients. There are no symptoms while sitting or lying down under static conditions.

Diagnosis

The diagnosis of BVP requires a bilaterally impaired or absent function of the angular vestibulo-ocular reflex (aVOR)/semicircular canals. This can be diagnosed for the high frequency range of the aVOR by a bilaterally pathological bedside head impulse test (bHIT) and for the low frequency range by bilaterally pathological bithermal caloric testing (sum of the maximal peak velocities of the slow phase caloric-induced nystagmus for stimulation with warm and cold water on each side < 10°/s). If the bHIT is unclear, aVOR function should be quantified by a video-oculography system (vHIT) (VOR gain on both sides < 0.7). Complementary tests are a) Romberg test; b) dynamic visual acuity (a decrease of ≥ 0.2 is pathological); and c) cervical and ocular vestibular-evoked myogenic potentials (c/oVEMP) for otolith function. There are the following subtypes of BVP depending on the affected anatomical structure and frequency range: impaired canal function in the low- or high-frequency VOR range only and/or otolith function only; the latter is very rare. If known, the etiology (e.g., due to ototoxicity, bilateral Menière’s disease, bilateral vestibular schwannoma) should be added to the diagnosis. Synonyms are bilateral vestibular failure, areflexia, or loss.

Observable ocular motor disorders

  • Bilateral deficit of vestibular-ocular reflex