Abstract

Background
and Objectives: While it is known that sleep have influence on emergence of rapid eye movements(REMs), namely saccades including fast component of nystagmus, whether spontaneous nystagmus due to vestibular imbalance presents during sleep is still unclear. The purpose of our study was to investigate whether tonic vestibular imbalance appeared as spontaneous nystagmus during the wakeful state could present during REM sleep. Materials and Method: Overnight polysomnography (PSG) was performed in 7 patients with spontaneous nystagmus due to vestibular neuritis (VN) and 7 control patients without dizziness or any nystagmus. The numbers of horizontal saccades were counted, during 3 minutes samples of the alert state before and after the PSG and the first and last REM sleep.
Results
All patients with VN showed significantly more saccades (fast phases of spontaneous nystagmus) towards the side contralateral to their vestibular lesion in the awake state before and after the PSG compared with control group. By contrast, during REM sleep the patients with VN showed no preponderance in saccade direction (p<0.05). Some brief nystagmoid jerks showed during REM sleep in both patients and controls equally and also had no preponderance in direction.
Conclusion
The tonic vestibular imbalance at peripheral level observed during alert state does not appear at the brainstem level during REM sleep. It is suggested that a de-afferentation of the peripheral vestibular input to the REM sleep generating areas may explain an absence of nystagmus during REM sleep in patients with VN. Key Words : Vestibular imbalance, Nystagmus, REM sleep

• Keywords: Vestibular imbalance;Nystagmus;REM sleep;