The evaluation of the semicircular canal function by a video Head Impulse Test in patients with lateral semicircular canal malformation

Abstract

The semicircular canal function in 10 ears of 5 patients with lateral semicircular canal malformation was evaluated using the video Head Impulse Test (vHIT). Traditionally, the semicircular canal function has been evaluated by caloric testing, and few cases have been evaluated by vHIT in patients with lateral semicircular canal malformation. In our results, 9 out of 10 ears showed normal findings on vHIT; however, both patients who underwent caloric testing showed unilateral or bilateral canal paresis. The reason for the dissociation between the two vestibular testing modalities may be that the membranous duct is enlarged due to lateral semicircular canal malformation, so in contrast to angular acceleration stimulation, as with vHIT, caloric testing shows a decreased function because thermal stimulation generates only local convection and cannot shift the cupula.