The second and third phases of caloric nystagmus

Abstract

Conclusion: The second and third phases of caloric nystagmus occur at a high rate. We can explain this phenomenon based on the hydrostatic pressure theory involved in perilymph. Objectives: To clarify the incidence of the second and third phases of caloric nystagmus, and to measure their intensity. Methods: The subjects were 12 healthy humans. The right ear was stimulated using iced water. The first phase of caloric nystagmus was recorded in a supine position. Immediately after the cessation of the first phase, each subject was repositioned to a prone position, and the second phase was recorded. Immediately after the halt of the second phase, each subject was repositioned to a supine position, and the third phase was recorded. Nystagmus was analyzed using three-dimensional video-oculography. Results: The mean value of maximum slow-phase velocity (MSV) of the first phase was 27.2°/s. All subjects revealed the second phase, and the direction was toward the right. The mean value of MSV was 7.2°/s. Nine subjects (75%) showed the third phase, and the direction was toward the left. The mean value of MSV was 2.7°/s.

Keywords:

• Video-oculography
• prone position
• hydrostatic pressure theory
• perilymph
• specific heat
• ossicles

Declaration of interest: The author reports no conflicts of interest. The author alone is responsible for the content and writing of the paper.