Vivid dreams are a feature of Parkinsonism. They usually have a strong visual content and are particularly marked during treatment with L-dopa or dopaminergic agents.
Visual hallucinations also occur during wakefulness in around 25% of those with idiopathic Parkinsonism but especially in Lewy body disease. They often involve strangers, but are not frightening. They are probably due to brief episodes of REM sleep intruding into wakefulness and occur particularly in those who have sleep-onset REM during polysomnography  and REM sleep demonstrated during naps in the day. Cataplexy does not occur.
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Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And Restoring Your Energy. Of the many things that we do just instinctively and do not give much of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.