Differential diagnosis of cerebellar and brain stem lesions by means of a visual suppression test

Abstract

Visual suppression is one method of demonstrating the function of visual fixation. Visual suppression is calculated by measuring the slow phase velocity of caloric nystagmus with eyes covered in darkness and that with eyes open, fixed in light.
Visual suppression was 54±12% in 52 normal adults.
Clinical cases of typical and localized lesions in the cerebellum or brain stem were selected and tested. Visual suppression of caloric nystagmus towards the lesion side was reduced or abolished in cases of cerebellar (especially flocculus or nodulus) lesions. Visual suppression of caloric nystagmus towards both sides was reduced or abolished in cases of diffuse or bilateral cerebellar lesions. Visual suppression of caloric nystagmus towards the lesioned side was strongly abolished and even augmentation of caloric nystagmus in light with eyes fixed was seen in cases of brain stem (especially pontine) lesions.
Thus, with this visual suppression test it can be determined whether the lesions are in the cerebellum or in the brain stem.