Vestibular laboratory tests: calorics, VNG, video head impulse, VEMP and posturography
- Examination
Lab tests measure each part of the balance organ: calorics and head impulse test the canals, VEMP tests the otolith organs.
See it in 3D: Semicircular canals · Vestibule · Vestibulocochlear nerve (VIII)
What it is
When the bedside exam is not enough, a vestibular laboratory can test each ear and each part of the labyrinth separately. Videonystagmography (VNG) records eye movements with infrared goggles and bundles oculomotor tests, positional tests and the caloric test. The caloric test checks the lateral semicircular canal of each ear at low frequency; the video head impulse test (vHIT) checks all six canals at high frequency; cervical and ocular VEMPs check the saccule and utricle; rotary chair and posturography look at both ears together and at how the patient uses vision, sensation and the vestibular system. Electrocochleography supports a diagnosis of endolymphatic hydrops. These tests localise and quantify a deficit; they do not replace the history, the HINTS exam in acute vertigo, or an MRI when a central cause is suspected.
Findings and interpretation
- Caloric mechanism: warm irrigation makes endolymph in the lateral canal flow toward the ampulla (excitation), cold flow away (inhibition); the fast phase is named by COWS.
- Bilateral weak or absent calorics: bilateral vestibulopathy (for example after aminoglycosides); confirm with rotary chair or vHIT; patients complain of oscillopsia and imbalance in the dark.
- Directional preponderance: nystagmus stronger in one direction regardless of the ear irrigated; it reflects spontaneous nystagmus or a tone imbalance and does not localise well.
- Caloric test in coma (oculovestibular reflex): with an intact brainstem, cold water causes tonic deviation of the eyes toward the irrigated ear without a fast phase; no movement suggests brainstem failure; a normal fast phase suggests the patient is awake.
- vHIT: small, fast, unpredictable head turns; goggles compare eye and head velocity (gain near 1 is normal); it can test lateral, anterior and posterior canals in their planes.
- Superior vestibular neuritis: abnormal lateral and anterior canals and oVEMP with normal posterior canal and cVEMP (inferior division spared).
- VEMP limitations: air-conducted responses disappear with conductive hearing loss; amplitude falls with age.
- Rotary chair: whole-body rotation; best for bilateral loss, children and follow-up of compensation.
- Computerised dynamic posturography: shows how the patient uses vision, proprioception and vestibular input; it describes function but does not localise the lesion; inconsistent (aphysiological) patterns suggest a functional component.
- Electrocochleography: an increased summating potential to action potential ratio (SP/AP) supports endolymphatic hydrops (Ménière disease).
How it is done
- Ask the patient to avoid vestibular suppressants, sedatives and alcohol before the test, for the period the laboratory sets.
- Examine the ears first: wax must be removed; with a perforated eardrum use air, not water, for calorics.
- VNG oculomotor tests: saccades, smooth pursuit and optokinetic responses; abnormalities point to a central cause.
- Record spontaneous and gaze-evoked nystagmus with and without fixation, then positional tests (Dix-Hallpike, supine roll).
- Calorics: supine, head raised 30 degrees (lateral canal vertical); irrigate each ear with water about 7 °C below and above body temperature, or air.
- Measure peak slow-phase velocity for the four irrigations; calculate canal paresis and directional preponderance; check fixation suppression.
- If there is no response, repeat with ice-cold water before concluding the labyrinth is dead.
- Add vHIT, VEMP, rotary chair, posturography or electrocochleography according to the clinical question.
Which test checks which part of the balance system
| Test | What it tests | Typical abnormal result | Classic use |
|---|---|---|---|
| Caloric (in VNG) | Lateral canal, each ear, low frequency | Canal paresis on one side; bilateral weakness | Vestibular neuritis, Ménière disease, schwannoma, bilateral loss |
| Video head impulse (vHIT) | All six canals, high frequency | Low gain with corrective saccades | Acute vestibular syndrome, neuritis by division |
| Cervical VEMP | Saccule and inferior vestibular nerve | Absent response; or low threshold and large amplitude | Inferior neuritis, Ménière disease; superior canal dehiscence |
| Ocular VEMP | Utricle and superior vestibular nerve | Absent response; or very large response | Superior neuritis; superior canal dehiscence |
| Rotary chair | Both labyrinths together | Low gain, phase lead | Bilateral vestibulopathy, children, compensation |
| Posturography | Use of vision, sensation and vestibular input | Falls in vestibular-dependent conditions; aphysiological pattern | Rehabilitation planning, functional dizziness |
| Electrocochleography | Cochlea and auditory nerve | Raised SP/AP ratio | Suspected endolymphatic hydrops |
Common mistakes
- Testing during an acute central vertigo: an emergency stroke workup is needed, not a laboratory appointment.
- Forgetting to remove wax or not checking for a perforation before water calorics.
- Reading a normal vHIT as «normal labyrinth»: calorics and VEMPs may still be abnormal.
- Testing while the patient takes vestibular suppressants, which blunt the responses.
- Ordering a full vestibular battery for typical BPPV, which is diagnosed and treated at the bedside.
Next step / Initial management
- Recurrent or chronic vertigo without a clear bedside diagnosis: routine referral to ENT or a vestibular laboratory for VNG with calorics, vHIT and VEMP, plus pure-tone audiometry.
- Asymmetric caloric weakness with asymmetric sensorineural hearing loss: MRI of the internal auditory canals to exclude a vestibular schwannoma (priority referral to ENT).
- Acute continuous vertigo with any central sign (HINTS), new neurological deficit or inability to walk: emergency referral the same hour; do not wait for lab tests.
- Peripheral deficit confirmed: vestibular rehabilitation is the main treatment; use vestibular suppressants only for a few days.
- Bilateral vestibulopathy: review ototoxic drugs (aminoglycosides) and refer to ENT and vestibular physiotherapy.
Test yourself
Think of the answer, then tap the question to see it.
During calorics, cold water in the right ear produces nystagmus beating to which side?
To the left (COWS: Cold Opposite, Warm Same).
A woman with recurrent vertigo, fluctuating low-tone hearing loss and fullness has 40 % right canal paresis but a normal vHIT. What does the dissociation suggest?
Ménière disease: hydrops affects low-frequency caloric responses while high-frequency vHIT function can be preserved.
A comatose patient shows no eye movement with ice-cold water in either ear. What does this indicate?
Loss of the oculovestibular reflex, consistent with severe brainstem dysfunction (one of the brainstem reflexes assessed in brain death).
A patient has sound-induced vertigo and cVEMP thresholds much lower than normal. Which diagnosis do you suspect?
Superior semicircular canal dehiscence (a third window); confirm with high-resolution temporal bone CT.
Elsewhere in DurgiPedia
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The structures of Durgical's 3D anatomy where it is found.
Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.
Sources: Caloric Testing (StatPearls Publishing (NCBI Bookshelf), 2025); Caloric Reflex Test (StatPearls Publishing (NCBI Bookshelf), 2023); VNG/ENG Testing (StatPearls Publishing (NCBI Bookshelf), 2024); Electrocochleography (StatPearls Publishing (NCBI Bookshelf), 2024); Vestibular Dysfunction (StatPearls Publishing (NCBI Bookshelf), 2023); The Video Head Impulse Test (Front Neurol) (Frontiers in Neurology (PubMed), 2017); Vestibular evoked myogenic potentials in practice: methods, pitfalls and clinical applications (Clin Neurophysiol Pract) (Clinical Neurophysiology Practice (PubMed), 2019); Balance Disorders (National Institute on Deafness and Other Communication Disorders (NIDCD), 2018).
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