Three Dimensional Analysis of Caloric Nystagmus and Effect of Visual Suppression in Cats

Background and Objectives:The caloric test is considered to be one of the most sensitive parameters in the diagnosis of peripheral vestibular disorders, although it can test only the function of the lateral semicircular canals. In this study, the authors measured the eye movements and visual suppression of caloric nystagmus in cats three dimensionally using a magnetic search coil system. Materials and Method:Three-dimensional (3-D) eye movement responses to an ice water caloric stimulus were studied with the six normal cats positioned in an upright position (lateral semicircular canal vertical). Visual suppression of caloric nystagmus was also investigated. Results:All animals showed eye movements in the horizontal, torsional and vertical planes. Of the three nystagmus components, the horizontal component showed the fastest eye velocity during caloric stimulation. In light, a slight, but certain degree of visual suppression in was recognized in cats. Conclusion:The caloric nystagmus response involves a complex eye movement response comprising the horizontal, vertical and torsional nystagmus components. The 3D analysis system with a magnetic search coil is useful to investigate the eye movement during caloric stimulation when the cat is awake. (Korean J Otolaryngol 2001;44:470-5)