Glossary

also known as: AVS

Sudden onset of vertigo, nausea, head-motion intolerance, and unsteadiness lasting at least 24 hours. Most cases are vestibular neuritis; a clinically important minority are posterior-circulation strokes.

also known as: gentamicin · tobramycin · streptomycin · amikacin

A class of antibiotics whose use is limited by ototoxicity. Gentamicin, streptomycin, and tobramycin are predominantly vestibulotoxic; amikacin and kanamycin are predominantly cochleotoxic.

also known as: directional asymmetry · interaural asymmetry

The difference in DVA loss between rightward and leftward (or upward and downward) head motions. In unilateral peripheral disease the asymmetry is the most useful screening signal; in bilateral disease it is near zero by definition.

also known as: ICVD · International Classification of Vestibular Disorders

International scientific society that issues consensus diagnostic criteria for vestibular disorders. Criteria documents referenced in this atlas: BVP (Strupp 2017), AUVP (Strupp 2022), MD (Lopez-Escamez 2015), VM (Lempert 2012/2022), PVP (Agrawal 2019), vascular vertigo (Kim 2022).

also known as: bedside HIT · Halmagyi-Curthoys test

Rapid, low-amplitude, unpredictable head rotation in the plane of a semicircular canal while the patient fixates a target. Catch-up saccades indicate an impaired VOR on that side. The 'H' in the HINTS exam.

also known as: BVP · bilateral vestibular failure · bilateral vestibular hypofunction

Chronic vestibular syndrome of unsteadiness and head-motion-induced oscillopsia caused by symmetric loss of vestibular function on both sides. Quantitative thresholds: vHIT gain <0.6 bilaterally OR caloric sum <6°/s per side. DVA shows severe symmetric loss with no directional asymmetry.

also known as: bithermal caloric · caloric irrigation

Vestibular test in which warm and cold water (or air) irrigation of the external auditory canal produces convection-driven endolymph flow in the horizontal canal, generating measurable nystagmus. Probes the low-frequency end of the VOR. Sensitive but unpleasant and impractical for surveillance.

also known as: cerebellar ataxia, neuropathy, vestibular areflexia syndrome

A late-onset hereditary syndrome combining cerebellar ataxia, sensory neuronopathy, and bilateral vestibular areflexia. Chronic cough is an under-recognised early clue. The RFC1 biallelic repeat expansion is the principal genetic cause.

also known as: corrective saccade · refixation saccade

Rapid eye movement that occurs after a head impulse to refixate the target when the VOR has failed to keep the eyes on it. Overt saccades occur after the head movement; covert saccades occur during it and can mask the VOR deficit on bedside testing.

also known as: central vestibular disease

Vestibular symptoms arising from lesions in the brainstem, cerebellum, or central vestibular pathways rather than the inner ear or eighth nerve. Posterior circulation stroke is the most common and most consequential central cause of acute vestibular syndrome.

also known as: covert catch-up saccade

A small, well-timed corrective saccade occurring during head motion rather than after it. Covert saccades restore retinal fixation faster than overt saccades and are the principal mechanism of DVA recovery after vestibular rehabilitation, even when peripheral VOR gain does not change.

also known as: cervical vestibular evoked myogenic potential

Vestibular evoked myogenic potential recorded from the sternocleidomastoid muscle. Probes saccule and inferior vestibular nerve function. Reduced or absent in inferior division neuritis and in vestibular schwannoma.

also known as: DVA · dynamic visual acuity test

Visual acuity measured during head motion, expressed as the difference (in logMAR) from static visual acuity. Quantifies the functional consequence of VOR impairment. The Bárány criteria recognise a ≥0.2 logMAR decrease as pathological.

also known as: content levels · reader levels

Three layered reader levels selectable from the sidebar. Foundation: core concepts only. Trainee: foundation plus clinical detail. Clinician: all content including advanced and research-level material. Print includes everything regardless of selection.

also known as: VOR gain

Ratio of compensatory eye velocity to head velocity during a head impulse. Normal value ≥0.8 for the horizontal canal. PVP threshold: 0.6–0.8 bilaterally. BVP threshold: <0.6 bilaterally.

also known as: Head-Impulse Nystagmus Test-of-Skew

Three-step bedside oculomotor examination for distinguishing central from peripheral causes of acute vestibular syndrome. 100% sensitive and 96% specific for central lesions in the original Kattah 2009 study, outperforming early MRI diffusion-weighted imaging. INFARCT mnemonic captures the dangerous pattern.

also known as: INFARCT

Mnemonic for the dangerous pattern on the HINTS exam: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test. Any one of these features in an acute vestibular syndrome patient raises concern for posterior circulation stroke.

also known as: labyrinthine artery occlusion

Vascular infarction of the inner ear via the labyrinthine artery (terminal AICA branch). Produces a peripheral-pattern HINTS exam despite vascular aetiology. Important because it may precede ponto-cerebellar AICA infarction by days to weeks.

also known as: log minimum angle of resolution

Logarithm (base 10) of the minimum angle of resolution in arc-minutes. Normal acuity (6/6 or 20/20) is 0 logMAR; each line on a logarithmic acuity chart corresponds to a 0.1 logMAR change. Used as the standard unit for DVA loss because differences are linear and additive.

also known as: Meniere disease · endolymphatic hydrops

Episodic inner-ear disorder of recurrent vertigo, fluctuating low-frequency sensorineural hearing loss, tinnitus, and aural fullness. Diagnosis is clinical and audiometric. The caloric–vHIT dissociation (abnormal caloric, normal vHIT) is a useful supporting feature.

also known as: MRI IAC · gadolinium MRI

Magnetic resonance imaging with gadolinium contrast of the internal auditory canal. Diagnostic gold standard for vestibular schwannoma. Posterior-circulation infarcts may be missed on initial diffusion-weighted imaging in up to 20% of cases within the first 48 hours.

also known as: spontaneous nystagmus

Involuntary, rhythmic eye movement with a slow phase (vestibular drive) and a fast corrective phase (saccade). Peripheral patterns are horizontal-torsional, unidirectional, and suppressed by fixation. Central patterns may be vertical, direction-changing, or fixation-resistant.

Subjective sensation of the world bouncing, jumping, or moving on the retina during head motion. The cardinal symptom of bilateral vestibular failure. Often described as inability to read street signs from a moving car or to recognise faces while walking.

also known as: vestibulotoxicity · drug-induced inner-ear damage

Drug- or chemical-induced damage to the inner ear, affecting the cochlea (cochleotoxicity), the vestibular system (vestibulotoxicity), or both. Aminoglycoside antibiotics and platinum-based chemotherapy are the principal causes.

also known as: ocular vestibular evoked myogenic potential

Vestibular evoked myogenic potential recorded from the inferior oblique muscle below the contralateral eye. Probes utricle and superior vestibular nerve function. Reduced or absent in superior division neuritis.

also known as: PCS · vertebrobasilar stroke

Stroke in the territory of the vertebral or basilar arteries — including the cerebellum, brainstem, and labyrinthine artery (terminal AICA branch). The most common and most consequential central cause of acute vestibular syndrome. MRI false-negative rate up to 20% within 48 hours.

Age-related sensorineural hearing loss, typically symmetric and high-frequency. Frequently accompanies presbyvestibulopathy because of shared cochlear and vestibular hair-cell ageing mechanisms.

also known as: PVP · age-related vestibular loss

Mild, bilateral, age-related VOR decline in adults ≥60 years. The Bárány 2019 thresholds sit between normal values and bilateral vestibulopathy: vHIT gain 0.6–0.8, caloric sum 6–25°/s per side, rotational chair gain 0.1–0.3. DVA pattern is the same as BVP but with smaller magnitude.

also known as: sinusoidal rotation · step rotation

Vestibular test in which the patient is rotated on a motorised chair while eye movements are recorded. Probes the mid-frequency end of the VOR (typically 0.1 Hz sinusoidal stimulation, V_max 50°/s). Used for BVP and PVP diagnostic thresholds.

Vestibular otolith organ in the vertically-oriented macula. Senses vertical linear acceleration. Innervated by the inferior vestibular nerve. Saccular function is probed by cVEMP.

also known as: vertical ocular misalignment

Vertical misalignment of the eyes detected by alternate cover test. Suggests a central lesion in the graviceptive pathway (brainstem or cerebellum). The 'T' component of the HINTS exam.

also known as: Snellen chart · Snellen fraction

Traditional visual-acuity notation expressed as a fraction (e.g. 6/6, 20/20) of test-distance over the distance at which a normal observer can read the same letters. Linearly equivalent to logMAR for clinical purposes.

also known as: SVA

Visual acuity measured with the head stationary. The baseline against which DVA is compared. Loss attributable to ocular pathology (refractive error, cataract, retinal disease) rather than vestibular dysfunction.

also known as: SVV

Test of the patient's perception of the vertical, probing otolith asymmetry. Abnormal in unilateral peripheral or central disease that produces graviceptive imbalance. Normal in symmetric bilateral disease (BVP, PVP, ototoxicity) because both sides are equally affected.

Vestibular otolith organ in the horizontally-oriented macula. Senses horizontal linear acceleration and head tilt. Innervated by the superior vestibular nerve. Utricular function is probed by oVEMP.

also known as: vestibular evoked myogenic potential

Family of vestibular tests using high-intensity sound or vibration to evoke myogenic responses driven by otolith activation. cVEMP probes saccule/inferior nerve; oVEMP probes utricle/superior nerve.

also known as: VM · migrainous vertigo

Episodic vertigo associated with current or past migraine history and migraine features in at least half of episodes. The most common cause of recurrent spontaneous vertigo in neurology clinics. Vestibular testing is heterogeneous and not localising; DVA can show mild symmetric loss in all four directions consistent with central pathophysiology.

also known as: AUVP · acute unilateral vestibulopathy

Acute peripheral vestibular syndrome of sustained vertigo, peripheral nystagmus, unilateral VOR reduction, and preserved hearing. Bárány 2022 criteria use the term acute unilateral vestibulopathy (AUVP). Most commonly attributed to HSV-1 reactivation in the vestibular ganglion.

also known as: vestibular physical therapy · VRT · gaze stabilisation exercise

Structured exercise programme to reduce dizziness and improve gaze stability after vestibular injury. Works principally through development of well-timed covert catch-up saccades. DVA is the most appropriate functional outcome measure.

also known as: acoustic neuroma · VS

Benign Schwann-cell tumour of the eighth cranial nerve, most often arising from the inferior vestibular division. Imaging-anchored disease (MRI is the gold standard). DVA is supporting evidence pre-operatively and the principal outcome measure post-surgically.

also known as: VOR

Three-neuron reflex arc that generates compensatory eye movements equal and opposite to head movements, stabilising gaze. Latency ~16 ms — too fast for any visually-driven correction. Quantified by VOR gain.

also known as: video head impulse test

Computerised head impulse test using a goggle-mounted video camera to measure eye velocity in response to high-acceleration head impulses. Probes the high-frequency end of the VOR. Quantifies VOR gain and detects covert saccades that may not be visible to the naked eye.