Effect of Unilateral Cerebral Lesions on Nystagmus: Bilateral Simultaneous Caloric and Optokinetic Nystagmus

It is known that slight differences in excitability between the right and left vestibular apparatus can be detected after bilateral simultaneous caloric stimulation of the labyrinths. A positive reaction is said to exist when the resulting nystagmus is present on direct forward gaze (second degree) or in addition present on lateral gaze to the side of the slow component (third degree).1,2A negative response is represented by no nystagmus, vertical nystagmus, or nystagmus present only on looking in the direction of the quick component (first degree). Brunner2,3has advocated the use of this test to differentiate between infra and supratentorial lesions. He found the majority of positive reactions in posterior fossa lesions. Anderson, Bergman, and Nathanson19found abnormalities on bilateral simultaneous caloric stimulation in 22% of patients with cerebral lesions and 83% of those with brain stem lesions. The sidedness of the caloric response in patients with