Overview and Purpose
The vHIT test (Video Head Impulse Test) is a vestibular assessment tool that objectively measures the function of the semicircular canals, particularly the horizontal canal. It is a critical diagnostic method for evaluating patients with dizziness, vertigo, and imbalance.
Key Research Findings
- High sensitivity and specificity: Recent studies show that vHIT has >90% sensitivity for detecting unilateral vestibular hypofunction when compared to caloric testing.
- Quantitative gain measurement: The primary metric is the VOR gain (vestibulo-ocular reflex). Normal gain values are typically >0.8, with corrective saccades (covert/overt) indicating pathology.
- Six-canal testing: Newer protocols allow assessment of all three semicircular canals (lateral, anterior, posterior) on each side, improving diagnostic scope for conditions like superior canal dehiscence and vestibular neuritis.
- Age-related changes: Research indicates that VOR gain declines slightly with age (by approximately 0.1 per decade), requiring age-adjusted normative data for accurate interpretation.
Methodological Considerations
Proper technique is essential. The head impulse must be passive, unpredictable in direction, and of high velocity (150–250°/s). Inadequate velocity or anticipation by the patient can produce false negative results. Eye tracking calibration must be performed before each recording session.
Clinical Integration
vHIT is most powerful when combined with caloric testing and VEMP (vestibular evoked myogenic potentials). This battery approach helps differentiate central vs. peripheral lesions and guides rehabilitation strategies such as vestibular rehabilitation therapy.
Emerging Research Directions
- Artificial intelligence algorithms for automated saccade detection and gain calculation.
- Portable vHIT devices for bedside and remote clinical use.
- Correlation between vHIT parameters and fall risk in elderly populations.
Conclusion: The vHIT test is a rapid, well-tolerated, and highly informative tool in the neuro-otology clinic. Ongoing research continues to refine its diagnostic accuracy and expand its clinical utility.