Evaluation of the Vestibular Function by Caloric Test.

The logarithms of maximal slow phase velocities (MSPV) of caloric nystagmuses showed normal distribution. Taking advantage of this fact, a presumptive mean value and standard deviation of the MSPV of caloric nystagmus were calculated. As a result, the normal range of total MSPV of caloric responses to 44°C and 30°C stimuli were assumed to be 10-70°/sec for each ear.In 413 patients with various kinds of inner ear disturbances, 21 cases showed bilateral vestibular hypofunction. In 248 cases showing a CP% below 26%, four cases showed unilateral hyper-active caloric responses and only two cases showed bilateral hyperactivity. In 144 cases showing a CP% of 26% or more, 13 cases showed unilateral hyperactive caloric responses.The mechanisms of hyperactivity of caloric responses to inner ear disturbances were surmised to involve overcompensation for unilateral vestibular paresis, emotional hypersensitivity of the patient at caloric test or other reasons. However, further observation of each case is clarify the cause.