INVESTIGATIONS ON THE CALORIC TEST

The author studied the theories of caloric nystagmus and their methods of the tests are classified.Necessary conditions for the caloric test are as follows:1) Easy performance of the test.2) Results of test are almost constant and the results obtained by any tester are less variable.3) Minimal inconvenience for the patient.4) The test is able to be performed repeatedly.First the author investigated the temperature and quantity of water for irrigation and discov-ered the suitable method for clinical test on normal sudjects. Furthermore the author confirmed statistically the influence of the position of head of the position of the eyes, an interval, and the use of Frenzel's spectacles upon the nystagmus. Atkinson's method, Z-test were also studied com-paratively.The outlines of the investigation are as follows:1) The stimulus is too strong and to excessive when the difference fo temperature of water and tbe body is 10°C or more. The preferable temperature is 27°C, 30°C or 44°C and the suitable quan-tity of water in 20cc or 50cc.2) Not only duration but latency and number of nystagmus is significant as an indicator of the caloric test.3) The best head position is 60° retroflection (this position is most sensitive to thermic stimul-ation), but a supine position with a pillow is also allowed for the clinical test.4) Observations on the nystagmus are difficult when eye position is directed to opposite side. While they are extremely easy when the eye position is directed about 30° to the side of nysta-gmus.5) Three minutes interval is too short. Six minutes give the more reliable results, but when the more exactness is required, about 10 minutes interval is advisable.6) The tests done with and without Frenzel's spectcle do not show difference of significance.7) Nystagmus is clearly observed in Atkinson's method, and the error is minimal, even if the tester is unskilled, and it is recommended as a simple clinical caloric test. This test should be adopted as a "Screening test".8) Z-test has little difference in latency, duration of nystagmus, standard deviation between the left and right ear, and so it should be performed by all means when the precise clinical examina-tion is required.