Sleep Nystagmus in Asymptomatic Healthy Individuals: A Novel Finding

Introduction: The CAVA device (https://www.uea.ac.uk/groups-and-centres/cava-project) is a medical diagnostic device that has been developed to allow the automatic diagnosis of vertigo in symptomatic individuals by using electro-oculography to continuously record their eye movements over a 30-day period. We have recently reviewed the data from our original healthy volunteer clinical trials and have made some novel discoveries.

Methods: In total, 17 healthy volunteer subjects with no history of vestibular disease were invited to wear the CAVA device for 30 days, in 2018, to assess the suitability of the device to detect periods of induced nystagmus. During this period, subjects' eye and head movements were monitored nearly continuously (23 out of 24 hours). Vertical and horizontal eye movement waveforms were downloaded from the CAVA device and analyzed automatically to identify episodes of periodic eye-movement (nystagmus); a more sensitive algorithm has been developed to assess and interpret the full dataset waveforms recently.

Results: Out of the 17 participants, 12 exhibited episodes of nystagmus at night when no other head movement is noted, hence likely during sleep. Both horizontal (82 episodes) and vertical (102 episodes) periods of nystagmus were recorded among individuals, the majority happened between 12:00 am and 6:00 am. Some individuals are more prone to prolonged and sustained periods of nystagmus during sleep; up to 3,003 seconds vertically and 2,673 seconds horizontally.

Conclusions: The use of the CAVA device has identified periods of nystagmus during episodes of sleep which has not been described in the medical literature thus far, a novel finding. The features of this nystagmus are inconsistent with our knowledge of how REM sleep manifests but may represent a consequence of dreaming and/or the physical expression of non-vestibular disease processes.