A STUDY OF PER- AND POST-ROTATORY NYSTAGMUS: ITS EVALUATION IN THE CLINICAL INVESTIGATION OF VESTIBULAR FUNCTION

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  • TOKUMASU K.
    Department of Oto-Rhino-Laryngology, Faculty of Medicine, University of Tokyo

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  • 前庭機能検査における回転中ならびに回転後眼振の検討
  • ゼンテイ キノウ ケンサ ニ オケル カイテン チュウ ナラビニ カイテン ゴガンシン ノ ケントウ

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Per-rotatory nystagmus was induced by constant angular acceleration of 3°sect2 for a limited time. Postrotatory nystagmus was induced by a sudden stop following constant angular rotation of 60°/sec. Stimuli were given by means of an electrically controlled rotating chamber and ocular movements were simultaneously recorded electronystagmographically. Totally 12 test-subjects showing normal caloric reaction were examined. Normal values were obtained with regard to the latency, duration, total amplitude and maximal eye-speed of the slow phase of per-and post-rotatory nystagmus. Experimental results showed that evaluation of rotatory tests should be done synthetically by considering all nystagmic elements. It is because there were only a few elements, among which correlation coefficients were over the level of the significant standard. The formular for the synthetic judgement by above-mentioned elements of per-and post-rotatory nystagmus were presented. Thirty-six patients whose caloric reaction is abnormal were examined by rotational test. They consisted of 16 cases with canalparesis (CP), 10 cases with combined form of canal paresis and directional preponderance (CP+DP), 6 cases with directional preponderance (DP) and 4 cases with spontaneous nystagmus (SN).<br>The results obtained led us to the following conclusions: -<br>1. Per-rotatory test surpasses post-rotatory test because the former is more sensitive in detecting slight vestibular abnormalities than latter.<br>2. CP groups showed abnormalities in the highest persentage than CP+DP and DP groups.<br>3. In CP cases CP-side does not show always less intensive reaction than that of the other side, while, in DP cases, DP-side always showed more intensive reaction than the other side, i.e. therefore, CP-side cannot be decided by rotational test, while DP-side can.<br>4. Bilateral hypofunction of rotatory nystagmus was observed in CP and CP+DP cases, but not in DP cases. This appears to correspond with the so-called compensatory stage of canal paresis described by Ruttin in 1911.<br>5. The second phase of post-rotatory nystagmus appears intensively towards DP-side. Therefore, it is considered that the senond phase of nystagmus shows the existence of DP of nystagmus.

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