RELATIONSHIP BETWEEN EXTERNAL AUDITORY CANAL TEMPERATURE AND CALORIC NYSTAGMUS:THE PROBLEM WITH THE ORDINARY COLD-WARM CALORIC TEST

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The cold-warm caloric test is performed with water irrigation, using a hot temperature of 44°C and a cold temperature of 30°C, which are thermally equidistant from the body temperature 37°C. However, the 30°C irrigation nearly always produces a stronger nystagmic response than that of the 44°C stimulation. The purpose of this study is to investigate the difference in nystagmic response between cold and hot stimulation. The achieved hot (44°C) and cold (30°C) water samples were prepared, and irrigation was with a disposable plastic syringe. Temperature changes in the external auditory canal were monitored by tympanic thermometry during the cold-warm caloric test. Maximal slow phase velocity and the duration of induced nystagmus were recorded on an electro-nystagmograph. The following conclusions were drawn; 1) The average normal external auditory canal temperature was 36.8°C, and there was no side difference between the right and left ears. External canal temperature was higher than that of the axilla. 2) When 20ml of 30°C water was instilled the temperature change in the external canal was larger than that in response to the 44°C water and the maximal slow phase velocity of nystagmus for cold stimulation was stronger than that for hot. However, the duration of nystagmus for the cold was not significantly longer than that of the hot stimulation. 3) Using 50ml cold water, the temperature change in the external canal was also larger than that observed when using hot, but the maximal slow phase velocity and the duration of nystagmus did not show significant differences between hot and cold. 4) The reason for hot water stimulation being weaker than that of cold water was that the temperture of the hot water dropped, i.e. with a disposable plastic syringe there was a temperature drop of 1°C at 44°C, despite the absence of a drop at 30°C at a room of 25°C. This means that 43°C water instead of 44°C was used for the hot irrigation while 30°C was used for the cold. 5) A 50ml irrigation or equipment for maintaining the temperature of hot water, is apparently necessary for a hot stimulation which produced a response as strong as that of the cold stimulation.
社団法人日本耳鼻咽喉科学会の論文

RELATIONSHIP BETWEEN EXTERNAL AUDITORY CANAL TEMPERATURE AND CALORIC NYSTAGMUS:THE PROBLEM WITH THE ORDINARY COLD-WARM CALORIC TEST

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