Pendular Seesaw Nystagmus: Disappearance With Monocular Occlusion

We report a case of pendular seesaw nystagmus caused by bitemporal hemianopia; the nystagmus disappeared while in darkness as previously described, but it also disappeared with monocular occlusion, which indicates the pivotal role of binocular vision in the pathogenesis.

Photo and Video Essay Section Editors: Melissa W. Ko, Dean M. Cestari, Peter Quiros, Kimberly M. Winges, MD MD MD MD Pendular Seesaw Nystagmus: Disappearance With Monocular Occlusion Xuefei Liu, MD, Yunqing Wu, MD, Hanqiu Jiang, MD, PhD, Jiawei Wang, MD, PhD, Shilei Cui, MD, PhD FIG. 1. Brain MRI before and after the surgery. A. Postcontrast T1 coronal and (B) sagittal MRI showed an enhanced mass on the left side of tubercle sella. The adjacent frontal and insular lobe was slightly compressed. C. After the surgery of tuberculum sellae meningioma resection, no obvious lesion was visible on T1 MRI. Abstract: We report a case of pendular seesaw nystagmus caused by bitemporal hemianopia; the nystagmus disappeared while in darkness as previously described, but it Department of Neurology, Beijing Tongren Hospital, Capital Medical University, Beijing, China. also disappeared with monocular occlusion, which indicates the pivotal role of binocular vision in the pathogenesis. Journal of Neuro-Ophthalmology 2022;42:e523–e525 doi: 10.1097/WNO.0000000000001471 © 2022 by North American Neuro-Ophthalmology Society The authors report no conflicts of interest. Xuefei Liu and Yunqing Wu are co– first authors. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the full text and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). Address correspondence to Shilei Cui, MD, PhD, Department of Neurology, Beijing Tongren Hospital, Capital Medical University, No. 1 Dongjiaominxiang Street, Dongcheng District, Beijing, China; E-mail: [e-mail] Liu et al: J Neuro-Ophthalmol 2022; 42: e523-e525 A 59-year-old woman had complained of oscillopsia lasting 6 months. This patient had had a tuberculum sellae meningioma (Fig. 1) removed via a left-sided frontolateral approach 3 years earlier. Before the surgery, she had experienced progressive bilateral visual loss for 4 years. Neuro-ophthalmological evaluation in the first month after e523 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay the surgery showed reduced visual acuity (right eye: 0.8; left eye: 0.2) and bilateral visual field defects (Fig. 2A). No abnormal eye movements were found at that time. Except for a 15year history of hypertension, she had no other medical history to report. Examination of the ocular fundus revealed bilateral optic disc pallor, and her pupillary light reflexes were normal with bilateral reduced visual acuity (right eye: 0.8; left eye: 0.3). Relative afferent pupillary defect was positive in her left eye, with a similar visual field defect (Fig. 2B) to that observed 3 years earlier. Ocular motility examination and video nystagmography revealed pendular seesaw nystagmus (pSSN) (1,2) characterized by rhythmic, torsional, and disjunctive vertical eye movement without a quick phase, in which one eye elevates and intorts, whereas the other eye depresses and extorts during the first half-cycle; the direction of vertical and torsional eye movements in each eye is reversed during the next half-cycle (see Video 1, Supplemental Digital Content 1, http://links.lww.com/WNO/A537). The eye movement was observed under different conditions: the nystagmus disappeared in darkness, when both eyes were closed, and in the light when only one eye was fixed on the visible target (see Video 2, Supplemental Digital Content 2, , http://links.lww.com/WNO/A538), but it reappeared when both eyes were fixed on the visible target, in the light or darkness. When the patient was in the supine position, the pSSN disappeared in the dark, but it reappeared when both eyes fixed on the visual target with decreased intensity. Then patient’s oscillopsia and nystagmus significantly resolved after the treatment of clonazepam (1 mg every 8 hours). FIG. 2. Humphrey visual field test showing similar visual field defect at different times during the follow-up period. A. One month after the surgery. B. Three years after the surgery. e524 Unlike jerky seesaw nystagmus (hemi-SSN), which may occur due to imbalance of central otolithic projections from vestibular nuclei to the interstitial nucleus of Cajal, most cases of classic pSSN have been reported in patients with lesions of the chiasm causing bitemporal hemianopia (e.g., giant suprasellar tumor or congenital achiasma, septo-optic dysplasia, chiasmal trauma) (2). Although the pathogenesis of pSSN still remains elusive, it has been supposed that disturbance in the visuovestibular system mediated by accessory optic system (AOS) may play a pivotal role, and lesions compressing the optic chiasm and the AOS could interrupt the transmission of retinal error signal to the inferior olivary nucleus (3–5). In most mammalian species, the AOS consists of 3 paired terminal nuclei near the mesodiencephalic border that receive direct retinal input predominantly from the contralateral eye through the accessory optic tract and project differentially to the dorsal cap of the inferior olive, which provides the only source of climbing fibers to the flocculonodular lobe of the cerebellum. Nuclei of AOS are responsible for visual–vestibular interaction, and they detect retinal image slip and report it to the oculomotor system for reflexive image stabilization (2). Yat-Ming Woo et al (6) proposed a double-hit hypothesis for pSSN from their case observation in which the optic chiasm and medial terminal nucleus are compressed by the lesion. In our case, brain MRI data showed that the only part of the brain involved was the optic chiasm, the left optic nerve, and adjacent frontal and insular lobes (Fig. 1), which suggests that isolated involvement of optic chiasm is sufficient to cause pSSN. Kim et al described one patient whose classic pSSN disappeared with the removal of visual fixation in darkness and while supine. They postulated that visual and otolithic inputs may be required to maintain pSSN (3). Similar changes were also observed in our case, except that the pSSN was still present (although decreased in intensity) when both eyes fixated in the light while supine. Based on 2 important facts, that is, that the AOS is responsible for visual–vestibular interaction and that the vestibulo-ocular movement pathway is the final common pathway involved in various types of eye movements, it is not difficult to understand that any change in vestibular input would influence the preexisting nystagmus. pSSN disappeared when the patient was not engaged in visual fixation, which is one of the most widely accepted manifestations. It has been reported in many cases before, but this is the first work to describe another important feature. Here, the nystagmus disappeared with unilateral visual fixation (both in the light and in the darkness). In other words, the appearance and disappearance of pSSN were controlled by bilateral and unilateral visual fixation without changes in peripheral vestibular input. The findings of our study further support that binocular visual input, not visual input alone, is Liu et al: J Neuro-Ophthalmol 2022; 42: e523-e525 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay crucial to generating pSSN. Whether this sign can be used in the topical diagnosis of SSN also needs more clinical observation. Considering the aforementioned features of pSSN, it is reasonable to recognize the importance of the preservation of geniculo-cortical function and to speculate whether the top-down active binocular fusion system would play a primary role in the generation of pSSN. Although some researchers suggested a fully contralateral retino-AOS projection, most studies support the presence of a small ipsilateral contingent of fibers, and the AOS may also receive projections from the visual cortex. However, this has not been fully established (7). Because of the possible neuroanatomical basis named above, the ipsilateral retino-AOS, cortical-AOS projections, or both may participate in the generation of pSSN. We hope to further establish the underlying mechanism in future. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: C. Shilei; b. Acquisition of data: L. Xuefei and W. Yunqing; c. Analysis and interpretation of data: C. Shilei, L. Xuefei, and W. Yunqing. Category 2: a. Drafting the manuscript: C. Shilei, L. Xuefei, and W. Yunqing; b. Revising it for intellectual content: C. Shilei, J. Hanqiu, and W. Jiawei. Category 3: a. Final approval of the completed manuscript: C. Shilei. Liu et al: J Neuro-Ophthalmol 2022; 42: e523-e525 ACKNOWLEDGMENTS The authors thank the patient and her family for granting permission to publish this information. The authors thank Chuntao Lai, MD, Xing Yan, MD, and LetPub (www.letpub. com) for their assistance during the preparation of this manuscript. REFERENCES 1. 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