Right posterior canalithiasis with gaze separation. This video shows classic and robust up-beating and geotropic rotary nystagmus in the right Dix-Hallpike position. Gaze to left reveals the pure up-beating component and gaze to the right reveals the pure rotary component. See the videos in the Ewald’s First Law section for a more detailed demonstration. Dissection of evoked nystagmus with gaze is useful in confusing cases and can clarify the canal of origin.
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