Assessment of semicircular canal function in benign paroxysmal positional vertigo using the video head impulse test and caloric test

Objective: To assess semicircular canal function in benign paroxysmal positional vertigo (BPPV) using the video head impulse test (vHIT) and caloric test.Methods: We retrospectively reviewed 39 patients with idiopathic BPPV who underwent both vHIT and the caloric test. Twenty-one patients had posterior BPPV (p-BPPV) and eighteen had horizontal BPPV (h-BPPV). Vestibulo-ocular reflex (VOR) gain and corrective saccades (CS) were analyzed in vHIT and canal paresis (CP) was calculated in the caloric test.Results: The mean VOR gain of the posterior canal in p-BPPV was 0.75 +/- 0.28 on the affected side, which was significantly smaller than that on the contralateral side (0.93 +/- 0.24, p = .00738). On the other hand, there were no significant differences in the VOR gain of the horizontal canal in h-BPPV between the affected and the contralateral sides (p = .769). The rates of the presence of CS were not significantly different between the affected canal and the contralateral canal either in p-BPPV (p = .111) or h-BPPV (p = .0599). The mean CP value in h-BPPV patients (43.5 +/- 31.3%) was significantly higher than that in p-BPPV patients (22.2 +/- 22.9%; p = .0184).Conclusion: The VOR gain of vHIT in the affected canal was significantly smaller than that in the contralateral canal in p-BPPV, but not in h-BPPV. The caloric responses of the affected canal are reduced to a significantly larger extent in h-BPPV compared to p-BPPV. These results suggest that BPPV affects the semicircular canal function differently depending on which semicircular canal is involved.