Mechanism of spontaneous upbeat nystagmus

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The tegmentum of the midbrain in particular the pretectal area has been considered responsible for upbeat nystagmus. Recently, however, Gilman et al. (1977) reported a 54 year old male who showed spontaneous upbeat nystagmus. Autopsy revealed infiltration of astrocytoma into rather an extensive area of the brainstem mainly in the Inferior Olivary Nucleus.<BR>We performed experiments in which the Inferior Olivary Nucleus was destroyed in cats and observed the upbeat nystagmus. However, the following autopsy showed that the area of destruction was localized not only at the Inferior Olivary Nucleus, but also at the Paramedian Reticular Nucleus, Hypoglossal Nucleus and Pyramidal Tract. However, no lesions were observed at the Vestibular Nuclei or upper brain stem.<BR>Clinically we experienced a case, 22 year old female, showing spontaneous upbeat nystagmus with forward gaze or eyes closed and central nervous lesions were suspected after a series of equilibrium tests, BSR, etc.<BR>We consider that the area of lower brain stem or the floor of the IV ventricle, midbrain tegmentum including cerebellar vermis in the vertical pursuit system play role in the occurrence of spontaneous upbeat nystagmus.
日本めまい平衡医学会の論文