温度性眼振検査に関する再検討

抄録

In the study of vestibule, certain authors recently said in their reports that the findings gained through caloric test were less valuable than those obtained from the examination of spontaneous or positional nystagmus. But I think caloric test can st ill be considered to be most reliable and important, when we determine whether there is any unilateral disorder of labyrinth. Various methods of irrigation in caloric test have been performed, but no method has been regarded as the stan-dard. HALLPIKE'S method is fairly popular, but the volume of the water irrigated differs from one researcher to another. It was recommended at the conference of Japan Medical Society in 1960 to supply an ear with 20 cc. of water in the present test and subsequently many otologists have followed this suggestion.
I doubted the accuracy of the result gained in caloric test in which 20 cc. of water is used for irrigation. In order to prove my doubt I compared the method using 20 cc. of water with HALLPIKE'S 40 sec. irrigation in normals and in patients. Duration, total amplitude and latency were employed as the indicators of caloric reaction. Abnormalities in electronystagmographic findings were also discussed. The followings are the conclusion.
1) Mean value of duration, total amplitude and latency of 20 cc. irrigation and for 40 sec. irrigation in normal subjects are as follows._??_
2) In three indicators, the minimal variation is statistically found in the duration of nystagmus, while greatest variation in total amplitude. The value of total amplitude increases more according as the intensity of stimulation such as water volume and temperature of irrigated water than the duration does. Therefore the latter should not be regard as only indicator.
3) Comparing the variation of the data in 20 cc. irrigation with that in 40 sec. irrigation, I find the former is significantly greater so long as total amplitude and duration concern. The variation of latency is little greater in the 40 sec. irrigation than in 20 cc., but it is not so statistically significant. In view of these findings, it is evident that the method of 40 sec. irrigation is better than that of 20 cc. irrigation.
4) The mean value of canal paresis % (CP%) is got by dividing the value of the difference of duration between the reactions of the left labyrinth and the right by the value of total duration and in the present case it is 4 %, while directional preponderance % (13P451)), which can be similarly figured out from the variation of the difference of duration between the left-beating and the right-beating nystagmus, is 7 %. The greatest value is 15% in CP% and 20% in DP%.
5) By the 20 cc. irrigation method no nystagmic response from the irrigation in one or both of the ears was found in 28% of the patients who show response in the 40 sec. irrigation, and 19% of those patients show the response which lies within the normal range of duration when 40 sec. irrigation method is applied to them. From this it is reasonable to presume that hyporeaction found in the 20 cc. irrigation method does not indicate the hypofunction of the labyrinth but is due to some technical and thermotransmissional insufficiency in the irrigation. So the 20 cc. irrigation cannot be considered satisfactory as a regular method of testing nystagmus.
6) Latency of induced nystagmus in the patients was a little longer than that in the normals, but this fact is negligible except in the case of 40 sec, irrigation of 44°C water. Latency is not influenced by the quantity of water and usually shows a constant value, but does not have any correlation with the duration. Latency is not suitable for an indicator of nystagmus.