Glossary

39 terms used throughout the atlas. Bookmark terms to build a personal study list.

AICA stroke(anterior inferior cerebellar artery stroke): Posterior-circulation stroke that may involve the labyrinthine artery, producing peripheral-pattern vHIT plus hearing loss. A 'pseudoneuritis' mimic of vestibular neuritis.
Alexander's law: Empirical rule that horizontal vestibular nystagmus intensifies on gaze in the direction of the fast phase. Peripheral nystagmus typically obeys this law.
Ampulla: Dilation at one end of each semicircular canal containing the crista ampullaris (sensory epithelium) and the cupula.
Anti-compensatory saccade: A saccade in the same direction as the head movement, generated by healthy subjects in the SHIMP paradigm to catch up to the head-fixed laser target.
AUVP(acute unilateral vestibulopathy, vestibular neuritis): Bárány Society term for vestibular neuritis. A clinical syndrome of acute, prolonged unilateral vestibular nerve dysfunction without hearing loss.
AVS(acute vestibular syndrome): Acute continuous vertigo lasting more than 24 hours, with nausea, head-motion intolerance, and gait unsteadiness. Differential includes vestibular neuritis, labyrinthitis, posterior circulation stroke.
Bilateral vestibulopathy(BVP, bilateral vestibular hypofunction): Chronic vestibular syndrome with bilaterally impaired VOR. Diagnostic criterion (Bárány 2017): bilateral horizontal vHIT gain < 0.6.
BPPV(benign paroxysmal positional vertigo): Brief positional vertigo from canalith debris in a semicircular canal. vHIT is typically normal; diagnosis is by positional manoeuvres (Dix-Hallpike, supine roll).
Caloric testing: Low-frequency vestibular test using warm/cool water or air irrigation of the external auditory canal. Stimulates the lateral canal at ≈ 0.003 Hz, complementary to high-frequency vHIT.
Caloric–vHIT dissociation: Reduced caloric response with preserved high-frequency vHIT gain. Highly specific for Meniere disease (≈ 84% specificity).
Covert saccade(covert corrective saccade): A corrective saccade that occurs during the head impulse, typically with latency 80–200 ms. Hidden to bedside examination; detectable only with vHIT. A marker of central compensation.
Cupula: Gelatinous membrane within the ampulla of each semicircular canal. Endolymph inertia deflects the cupula during head rotation, bending hair-cell stereocilia and modulating their firing rate.
Gain classification: Five-tier system: normal (≥ 0.80), mild (0.70–0.79), moderate (0.40–0.69), severe (0.20–0.39), profound (< 0.20).
HIMP(head impulse paradigm): The conventional vHIT protocol. Patient fixates an earth-fixed target while head impulses are delivered. Measures the VOR's capacity to compensate for head motion.
HINTS(Head Impulse, Nystagmus, Test of Skew): Three-step bedside oculomotor examination for distinguishing acute peripheral vestibular syndrome from posterior circulation stroke. Achieves 100% sensitivity / 96% specificity in trained hands.
HINTS-plus: HINTS plus bedside hearing testing. New hearing loss on the side of the deficient HIT raises suspicion for AICA-territory stroke.
Inferior vestibular nerve: Smaller division of the vestibular nerve. Innervates the posterior canal and saccule. Rarely affected in isolation; isolated inferior neuritis is a distinct, rare entity.
Labyrinthitis: Acute unilateral vestibular loss with concurrent sudden hearing loss. Pathology localises to the labyrinth (vestibule + cochlea) rather than to the vestibular nerve alone.
LARP(left anterior–right posterior): Vertical canal plane containing the left anterior and right posterior canals. Tested by pitching the head 35–45° down or up in the plane oriented 45° from sagittal.
Meniere disease(MD, endolymphatic hydrops): Episodic vertigo with fluctuating low-frequency hearing loss, aural fullness, and tinnitus. Associated with endolymphatic hydrops. Vestibular function tests often show caloric–vHIT dissociation.
Nystagmus: Involuntary rhythmic eye movement with a slow vestibular phase and a fast resetting phase. Direction is conventionally named for the fast phase.
Oscillopsia: Perception that the visual world moves with head motion, due to inadequate VOR. Characteristic of bilateral vestibulopathy.
Otolith organs: Collective term for the utricle and saccule. Tested clinically with VEMPs (cervical and ocular).
Overt saccade(overt corrective saccade): A corrective saccade that occurs after the head has returned to rest (typically > 220 ms). Visible at the bedside and a marker of acute, uncompensated VOR deficit.
PICA stroke(posterior inferior cerebellar artery stroke): Cerebellar/lateral medullary stroke. vHIT often shows symmetric mild bilateral gain reduction with very small saccades — the central pattern.
Push–pull principle: Paired canals on opposite sides of the head sense the same angular rotation in opposite directions. Excitation of one drives the VOR; the contralateral canal is inhibited.
RALP(right anterior–left posterior): Vertical canal plane containing the right anterior and left posterior canals.
Saccade: A rapid, ballistic eye movement that re-fixates gaze on a target. Corrective saccades in vHIT compensate for an inadequate VOR.
Saccule: Otolith organ that detects linear acceleration in the vertical plane. Innervated by the inferior vestibular nerve.
Semicircular canal(SCC): Three orthogonal fluid-filled canals (lateral, anterior, posterior) in each labyrinth that detect angular head acceleration. Each canal has an ampulla containing a cupula and hair cells.
SHIMP(suppression head impulse paradigm): vHIT variant introduced by MacDougall and Curthoys (2016). Patient fixates a head-fixed laser; healthy subjects generate an anti-compensatory saccade after the impulse. Reduced peak SHIMP saccade velocity indicates canal deficit.
Skew deviation: Vertical misalignment of the eyes from vestibular tone imbalance. In acute vestibular syndrome, the presence of skew suggests a central lesion.
Superior vestibular nerve: Larger division of the vestibular nerve. Innervates the lateral canal, anterior canal, and utricle. Preferentially affected in vestibular neuritis (~90% of cases).
Utricle: Otolith organ that detects linear acceleration in the horizontal plane (and head tilt). Innervated by the superior vestibular nerve.
Vestibular migraine(VM): Episodic vestibular disorder fulfilling Bárány/IHS criteria. Interictal vHIT is usually normal but mild asymmetries may be found; central oculomotor abnormalities are common.
Vestibular schwannoma(acoustic neuroma): Benign tumour of Schwann cells arising from the vestibular nerve, typically in the internal auditory canal. Hearing loss is usually the presenting symptom; vHIT may show unilateral canal-specific gain reduction.
vHIT(video head impulse test): Quantitative head impulse test using head-mounted goggles and high-speed video oculography. Validated against scleral search coils (MacDougall 2009).
VOR(vestibulo-ocular reflex): A three-neuron reflex that generates a compensatory eye movement opposite to head rotation, stabilising the visual image on the retina during head motion.
VOR gain: The ratio of eye velocity to head velocity during the head impulse. A normal lateral-canal VOR gain is ≈ 0.95. Values below 0.80 are pathological.