gms | German Medical Science

The caloric test provides side-separated excitability findings for the lateral semicircular canal. Responses to warm and cold stimulation differ in both quality and quantity. Routine caloric tests start with a warm irrigation on the right side following guidelines of the ADANO (Association of German Audiologists and Neurootologists). The question arises whether the side of initial stimulation has an influence on the subsequent responses.

This study retrospectively examined electronystagmographic recordings from 100 patients with normal findings. The measurement of slow-phase velocity showed that the warm irrigation differed significantly (p=0.00003, Wilcoxon test) in favor of the left side, which is irrigated after the right side. The subsequent cold stimulation showed no significant difference between the left and right side (p=0.306, Wilcoxon test). Also, as in other studies, the sum of slow-phase velocities was significantly greater for the warm irrigation than for the cold one (p=0.000001, Wilcoxon test).

The investigations show the limited validity of the Jonkees formula with its equal weighting of all responses. The increased response intensity in the second warm irrigation is not easy to explain, since central influences like storage effects do not seem plausible because of the reverse nystagmus direction of the second irrigation.