Analysis Of Caloric Nystagmus Research Articles

Computer analysis of fixation-suppression of caloric nystagmus.

Effects of the ocular fixation upon caloric nystagmus were quantitatively analyzed and compared between normal subjects and patients by using a PDP 11/40 computer. The slow-phase velocity was the best parameter to separate normal from abnormal visual fixation. An analysis of caloric nystagmus with failure of fixation-suppression (FFS) made it possible to classify patterns of FFS into three types. The combination of FFS with impairment of the optokinetic responses provides a useful diagnostic tool with respect to lesions located between the brain stem and the cerebellum.

Fixation-suppression of caloric nystagmus in normal subjects

Effects of ocular fixation upon caloric nystagmus have been used as a routine test. Percentage reduction in slow-phase velocity of caloric nystagmus induced by ocular fixation, however, varies depending upon the test condition employed.In the present experiment, we standardized the effects of ocular fixation upon caloric nystagmus in 58 normal individuals. The electronystagmographic test was performed in total darkness. The caloric stimulus was 50ml water, most often 30°C or 44°C, sometimes 20°C, for an irrigation period of 20 sec, with about 7-minute intervals. Subjects were requested to fix their gaze upon a spot on the ceiling about 3m away during the maximum intensity of slow-phase velocity for 10 sec. The amount of reduction of slow-phase velocity induced by ocular fixation was obtained during the first half of the 10-sec period and compared with the control period. The percentage reduction in slow-phase velocity induced by ocular fixation did not depend upon the temperature of the water applied as a caloric stimulus. The mean percentage reduction in slow-phase velocity induced was about 82±12%. On the basis of these results, fixation-suppression of caloric nystagmus was studied in 669 consecutive cases. An analysis of caloric nystagmus with failure of fixation-suppression (FFS) made it possible to classify patterns of FFS into three types. Together with the recent anatomical and physiological data, the underlying neuroanatomical substrates responsible for the FFS was discussed.

Caloric Pattern Test with Special Reference to Failure of Fixation-Suppression

Fixation-suppression of caloric nystagmus was studied in 1230 consecutive cases. An analysis of caloric nystagmus with failure of fixation-suppression (FFS) made it possible to classify patterns of FFS into three types: Type I: FFS was observed bilaterally in caloric nystagmus; Type II: FFS was recognized unilaterally on either side; Type III: FFS was seen in either direction of nystagmus. On the basis of these three types, the underlying neuroanatomical substrate responsible for FFS is discussed.

Clinical significance of visual fixation upon caloric nystagmus-caloric pattern test- (author's transl)

The effect of opening of the eyes and of ocular fixation upon caloric nystagmus has been routinely tested in our neurotological assessment of patients since 1974. All cases who showed a sign of FFS (Failure of Fixation-Suppression of Caloric Nystagmus) were found to have central nervous 'system '.lesions, especially posterior fossa lesions. From an analysis of caloric nystagmus with the sign of FFS, patterns of FFS were classified into the following three types. Type I Visual fixation failed to suppress caloric nystagmus to both directions. In this type, diffuse involvement of the central nervous system such as cerebellar degeneration, organic mercurials intoxication and myoclonus epilepsy was included. Type II : Visual suppression of caloric nystagmus could not be observed on either side regard-less of water temperature applied as caloric' stimuli. In this type, cerebellopontine angle syndrome such as acoustic tumor, meningioma, epidermoid and arachnoiditis was included. Type III: Visual fixation failed to suppress caloric nystagmus to either direction depending upon caloric stimuli. In this type, vascular disorder, head trauma and unilaterally located tumor of the cerebellar hemisphere were included. On the basis of our clinical data classified above, underlying neuroanatomical mechanism was discussed.