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

Abstract

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.

Keywords: BPPV; caloric test; corrective saccade; vHIT; vestibulo‐ocular reflex.

FIGURE 1

The VOR gain in vHIT of the affected canal and the contralateral canal in BPPV patients. (A) The VOR gain of the affected and contralateral sides of the posterior semicircular canals in patients with p‐BPPV (N = 21). (B) The VOR gain of the affected and contralateral sides of the horizontal semicircular canals in patients with h‐BPPV (N = 18). *p < .05.

FIGURE 2

The results of vHIT in a patient with BPPV of the right posterior semicircular canal. vHIT showed reduced VOR gain (0.47) with the presence of corrective saccades during head impulses to the right posterior semicircular canal (red circle). The gains of the other semicircular canals were within normal limits. The caloric testing of this patient gave normal responses on both sides.

FIGURE 3

Schematic diagram of endolymphatic flow during vHIT in p‐BPPV (A) and h‐BPPV (B). (A) In p‐BPPV, the debris in the posterior semicircular canal is aggregated in the lowest part of the canal in the upright position, disturbing the endolymphatic flow (yellow arrows) during rapid head turns along the plane of the posterior canal (red arrows). (B) In h‐BPPV, the debris in the horizontal semicircular canal is dispersed and the disturbance of the endolymphatic flow (yellow arrows) during horizontal head turns (red arrows) is minimal.