A study of five parameters of calorically-induced nystagmus in the clinical situation

Latency, duration, and amplitude of response, frequency of nystagmic beats, and speed of the slow component of calorically-induced nystagmus were studied by ENG in 14 normal-hearing adults. Attention was directed toward differences as a function of stimulus temperature (30 degrees C vs 44 degrees C) and side of stimulation. Nystagmus amplitudes were significantly larger from R ear as compared to L ear irrigations, and from cool as compared to warm. Ssc's from cool irrigations were also significantly larger than from warm. A series of t-tests computed for correlated samples indicated that the R ear 30 degrees irrigation, which was the first stimulus for all Ss, was responsible for the significant differences. Implications of the need for research on caloric interstimulus intervals and vestibular response fatigue were presented, and a procedure outlined to avoid erroneous results in caloric testing.