A high-speed camera test that measures how well each of the six semicircular canals is functioning by tracking the eye’s compensatory response to rapid head movements. The most canal-specific vestibular function test available in clinic.
Medical definition
The video head impulse test (vHIT) is an objective measurement of the vestibulo-ocular reflex (VOR) in each of the six semicircular canals. Small, lightweight goggles containing a high-speed infrared camera (250 frames per second) are fitted to the patient. The clinician delivers brief, unpredictable, small-amplitude head impulses in the plane of each canal pair while the patient fixates on a target. The camera tracks eye velocity and head velocity simultaneously. In a healthy canal, the eyes move at exactly the same speed as the head in the opposite direction (VOR gain = 1.0), keeping the visual target stable. In a canal with reduced function, the eyes lag behind and a catch-up saccade is seen. VOR gain below 0.8 in a canal, or the presence of covert or overt saccades, indicates hypofunction in that canal.
Why it matters for vertigo
The vHIT provides canal-specific information that caloric testing cannot. Caloric testing only stimulates the horizontal canals; vHIT can test all six canals (three per side) in a 10-minute session. It is particularly useful for: diagnosing vestibular neuritis (reduced VOR gain in the affected horizontal canal), evaluating bilateral vestibulopathy (reduced gain bilaterally), identifying which canal is affected in complex BPPV cases, and monitoring VOR recovery after vestibular neuritis or surgical labyrinthectomy. In the acute setting, a normal vHIT in a patient with apparent “vestibular neuritis” is a red flag — it makes a central cause more likely and drives the HINTS exam interpretation toward imaging.
Where I see this in clinic
Prime ENT Center in Hardoi has vHIT capability as part of the full VNG system. I use it for any patient where I need canal-specific function data — bilateral vestibulopathy workup, post-neuritis recovery assessment, and complex BPPV cases where the canal cannot be identified by Dix-Hallpike alone. For online consultations, vHIT results that patients bring from other centres are often the single most informative document in the file. A vHIT report showing unilateral horizontal canal hypofunction with covert saccades, combined with a history of sudden severe vertigo three months ago, tells me almost everything I need to know about that patient’s diagnosis.
Related terms
VNG – the full battery that includes vHIT alongside caloric and positional testing. Caloric test – tests horizontal canals only; vHIT tests all six. Vestibular neuritis – shows reduced horizontal canal gain on vHIT. Bilateral vestibulopathy – bilateral low VOR gain on vHIT is the defining finding.
Medical Disclaimer: This glossary entry is for educational purposes only. Consult Dr. Prateek Porwal directly. WhatsApp: 7393062200.