1 Influences on the Post-Caloric Nystagmus

Objective: The secondary phase of caloric nystagmus (CN) can be induced by postural change after the primary phase has ended. What is the mechanism of postural change for the generation of secondary phase of CN is investigated. Design: Postural changes consisted of changing the animal’s position from prone to diving (prone-diving) position (n=10), or from diving to prone (diving-prone) position (n=5), or from prone during irrigation then diving immediately after irrigation, and repostioned to prone (prone‧diving-prone) position (n=5). Caloric test was performed on the ears of guinea pigs by irrigating 5 mL ice water over 5 s. Mater ials: Twenty guinea pigs were used. Setting: University hospital Results: After the primary phase CN was finished, secondary phase could be successfully provoked in 7 (70%) out of 10 animals, by changing the animal’s position from prone to diving position (stimulated otolithic input). In diving-prone position (change in static otolithic input), 40% of animals had increased intensity of secondary phase CN, but the direction of both primary phas