EOG findings in patients with lesions in cerebellar peduncles

EOG tests were performed in patients with lesions in either the superior or the middle cerebellar peduncle, because these patients showed cerebellar signs and symptoms and were difficult to distinguish from patients with cerebellar lesions symptomatically. EOGs of these patients showed a predominant decrease of pursuit gains and OKN velocity gains toward the lesioned side, whereas the percent reduction of fixation-suppression of caloric nystagmus decreased predominantly toward the side contralateral to the lesioned side, regardless of whether lesions were located either in the superior or the middle cerebellar peduncle. The present EOGs are best interpreted as a corresponding to a deficit of the neuronal events of the flocculus in the monkey and are solely ascribed to lesions in the cerebellar peduncles, because even well-defined cerebellar lesions on one side showed bilateral impairments of these visually induced eye movements.