Vestibular

Vestibular refers to the sensory system and anatomical structures in the inner ear that regulate balance, spatial orientation, and eye movements. The term derives from the Latin vestibulum meaning entrance or vestibule, reflecting its role in sensing head position relative to gravity and movement as a gateway to coordinating posture and gaze.

The vestibular apparatus consists of the semicircular canals and the otolithic organs (the utricle and saccule) housed in the bony labyrinth of the inner ear. The semicircular canals detect angular (rotational) head movements in three dimensions, while the utricle and saccule detect linear acceleration and head position relative to gravity. Sensory hair cells within these structures transduce mechanical stimulation into neural signals that travel via the vestibular nerve, a branch of the vestibulocochlear nerve (cranial nerve VIII).

Central processing involves the vestibular nuclei in the brainstem, which integrate signals from both ears and coordinate motor responses. The vestibulo-ocular reflex stabilizes gaze during head movement by coordinating eye movements, and the cerebellum, particularly the flocculonodular lobe, assists with balance and motor control. Perception of motion and spatial orientation also involves thalamic and cortical pathways.

Clinical relevance encompasses a range of vestibular disorders, including benign paroxysmal positional vertigo (BPPV), Menière’s disease, vestibular neuritis, and labyrinthitis. Symptoms typically include vertigo, dizziness, imbalance, and nystagmus. Diagnosis employs tests such as the Dix-Hallpike maneuver, caloric testing, and video head impulse testing. Treatments focus on rehabilitative therapy (vestibular rehabilitation), canalith repositioning maneuvers for BPPV, and symptom management with medications; surgical options are rare and reserved for refractory cases.