vestibulooculaire

Vestibulo-oculaire, or vestibulo-occular system, refers to the neural circuitry that stabilizes gaze during head movements by generating compensatory eye movements. It encompasses the vestibular sensory organs in the inner ear—the semicircular canals and otolith organs—the vestibular nerve, brainstem vestibular nuclei, and projections to the oculomotor and abducens nuclei via pathways such as the medial longitudinal fasciculus. The principal reflex associated with this system is the vestibulo-ocular reflex (VOR).

Function and physiology: The semicircular canals detect angular head acceleration; otolith organs sense linear acceleration and head position relative to gravity. A head turn produces a signal that, after minimal neural latency, triggers an eye movement in the opposite direction with equal velocity, stabilizing the visual image on the retina. The VOR operates as a velocity sensor with a gain close to one in healthy individuals; it can be modulated by gaze position, visual input, and learning. In parallel, the optokinetic system helps stabilize images over longer movements.

Clinical significance and testing: Impairment of vestibulo-oculaire function can cause vertigo, oscillopsia, and nystagmus, affecting balance and vision. Common tests include the head impulse test (HIT) to assess high-acceleration VOR, caloric testing for low-frequency stimulation, and rotary chair testing. The video head impulse test (vHIT) provides quantitative VOR gain and phase. Bilateral vestibulopathy reduces VOR, causing unstable gaze; causes include degeneration, infection, trauma, or ototoxic medications.

Notes: In clinical context, the term is sometimes used interchangeably with vestibular-ocular reflex or vestibulo-ocular pathways; proper assessment requires integration of vestibular, visual, and proprioceptive information.