[THE VIDEO HEAD IMPULSE TEST (VHIT): CAN WE RELY ON THE GAIN PARAMETER ALONE?]

Abstract

Introduction: While the bedside head impulse test evaluates the presence of refixation saccades (RS) as a measure of failing vestibulo-ocular reflex (VOR) the VOR gain calculated by the video head-impulse test (vHIT) is considered the primary measure for semicircular canal function while the role RS is still under evaluation.

Aims: To evaluate the benefit of various RS characteristics towards the diagnosis of the left horizontal semicircular function by vHIT.

Methods: The vHIT recordings of 40 patients with left sided horizontal VOR gains <0.8 were retrospectively evaluated for the presence of RS. The study groups included 20 patients with a final diagnosis of left horizontal semicircular canal dysfunction and 20 patients for whom vestibular dysfunction was ruled out.

Results: Gain values > 0.72 were found in all patients with no vestibular disease, and in 4 (20%) patients having vestibulopathy. Significantly higher average left-sided RS velocity and frequency were found among the vestibular patients. VOR gain < 0.72 was found to be highly specific for the diagnosis of vestibular dysfunction. However, for gain values in the range of 0.72-0.79 the presence of RS with frequency > 80% improved vHIT sensitivity.

Conclusions: Although VOR gain<0.8 is considered to reflect dysfunction, a significant false positive rate for left-sided horizontal vHIT was found for gains in the range of 0.72-0.79. The presence of RS with frequency >80% could improve vHIT diagnostic accuracy in these patients.