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Jaclyn Hwang, Yaping Joyce Liao; Dramatic Fixation Instability in Peripheral Vestibulopathies without Visual Feedback Compared with Central Vestibulopathies. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2916.
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Eye movement abnormalities are common in central and peripheral vestibulopathies, and characterization of eye movements can help teach us important ways to localize the lesion. Eye movement characterization has also been used to triage dizzy patients in the acute setting to determine if this may be an emergency requiring brain imaging (Kattah, Stroke, 2009). In this study, we compared and contrasted eye movement findings during a simple fixation task in patients with central and peripheral vestibulopathies.
We performed detailed neuro-ophthalmic examination in 10 patients with peripheral and 10 patients with central vestibulopathies. We assessed visual fixation with and without visual feedback using 60-Hz binocular 3D infrared oculography. Fixation target at distance in the light was displayed using a custom-made LED board. Fixation target in the dark was displayed within the infrared recording goggle and turned on and off to assess rapid changes in eye position.
In patients with peripheral vestibulopathies, such as acoustic neuromas or vestibular neuronitis, visual fixation of a distant target was typically good, with rare, small amplitude square wave jerks that were also found in normals. Once fixation target was removed, however, patients’ fixation often rapidly decompensated, exhibiting deviations of eye positions, often in square wave jerk waveform that may be accompanied by a torsional nystagmus. The fixation instability pattern was different in patients with central vestibulopathies, such as Wallenberg syndrome or brainstem cavernous malformations. With visual feedback, patients typically exhibited uni- or multi-directional oscillations initiated by a slow phase. Once fixation target was removed, patients exhibited relatively less change in eye movement waveforms during fixation.
We confirmed previously reported unmasking of fixation instability in the dark without visual feedback in peripheral vestibulopathies (Hirvonen, Eur Arch Otorhinolaryngol, 2012) and showed that fixation in central vestibulopathies was less affected by visual feedback, consistent with failure of fixation suppression in central causes. We propose that a useful test to distinguish peripheral and central vestibulopathies is to observe patient eye movement behavior during fixation with and without visual feedback, ideally in the dark.
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