[Visual suppression test].

The visual suppression test is one of the methods measuring the function of visual fixation. It is carried out by recording the caloric nystagmus by electronystagmography and comparing the maximum slow phase velocity of caloric nystagmus in the darkness and the slow phase velocity in the light with eyes opened. In 50 normal adults aged 16 to 31 years, the score of the visual suppression of the slow phase velocity of caloric nystagmus was 69.9 +/- 18.5%. Visual suppression was also studied in 125 cases with various kinds of vestibular diseases. The results showed that: 1. In cases with peripheral vestibular diseases, the visual suppression was normal (visual suppression over 50%). 2. In cases with cerebellar diseases, the visual suppression might be reduced (visual suppression 40%-10%) or abolished (visual suppression under 10%). It means that the flocculus or nodulus had been directly or indirectly impaired. 3. In brain stem lesions, the visual suppression might be reduced, abolished or the caloric nystagmus might even show augmentation in light (visual suppression negative). It means that the paramedian pontine reticular formation had been impaired. 4. In case of CP angle tumor, owing to compression to the vestibulo-cerebellum or brain stem, the visual suppression might be abnormal. 5. In case of congenital nystagmus, visual suppression varied from normal to abolished. Thus, the visual suppression test is useful in differential diagnosis of the central and peripheral vestibular diseases.