Visual and Positional Modulation of Pendular Seesaw Nystagmus: Implications for the Mechanism

Background: The mechanisms of pendular seesaw nystagmus (SSN) remain unknown. Methods: We evaluated modulation of pendular SSN by removal of visual fixation, convergence, and positional changes in 2 patients, one with bitemporal hemianopia due to a traumatic damage of the optic chiasm and the other with platybasia compressing the medulla and lower cerebellum. Results: In both patients, the pendular SSN markedly decreased or disappeared with convergence, without visual fixation in darkness, during static head tilt toward each shoulder while sitting and while supine. Conclusions: The similar patterns of nystagmus modulation observed in our patients with a different etiology indicate a common role of both visual and otolithic inputs in generating pendular SSN. Address correspondence to Ji-Soo Kim, MD, PhD, Department of Neurology, College of Medicine, Seoul National University Dizziness Center, Clinical Neuroscience Center, and Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 13620, Korea; E-mail: jisookim@snu.ac.kr J.-S. Kim serves as an Associate Editor of Frontiers in Neuro-otology and on the Editorial Boards of the Journal of Clinical Neurology, Frontiers in Neuro-ophthalmology, Journal of Neuro-ophthalmology, Journal of Neurology, Medicine, and Journal of Vestibular Research. The remaining authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (https://ift.tt/2BFTkP1). © 2018 by North American Neuro-Ophthalmology Society

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