Evaluation of vertical semicircular canal function by the caloric test--a study on patients with benign paroxysmal positional vertigo.

The morbidity of benign paroxysmal positional vertigo (BPPV) was investigated from the functional standpoint by analyzing nystagmus elicited by the caloric test. As a result of an investigation of the three (horizontal, vertical and torsional) components of the nystagmus elicited by the caloric stimulus (cold water), the vertical nystagmus differed in direction between the left and the right ear in 3 out of the 4 BPPV cases. The vertical nystagmus elicited by the caloric stimulus reflected the functions of the anterior and posterior semicircular canals, and investigation of the difference in function between the anterior and posterior semicircular canal from the direction of the vertical nystagmus appeared to be feasible.