This rare condition is the result of abnormalities of the voltage gated potassium channels usually due to the production of auto-antibodies due to malignancy. It represents a form of limbic encephalitis. There is a reduction in sleep spindles and stages 3 and 4 NREM sleep, but muscle tone during REM sleep is retained and dream enactment similar to the REM sleep behaviour disorder is common. Insomnia, hallucinations, intense anxiety and delirium are characteristic. Hypertension, tachycardia, sweating and fever are common. The disorder may remit or progress and may respond to plasma exchange.
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