Narcolepsy is a disorder of the relationship between sleep and wakefulness. This particularly affects REM sleep where features of REM sleep intrude into wakefulness and non-REM sleep. The cardinal symptoms are excessive daytime somnolence, cataplexy, hypnogogic hallucinations and sleep paralysis. Diagnosis is made using polysomnography and multiple sleep latency test showing short sleep latency and sleep onset REM. Narcolepsy with cataplexy is caused by loss of hypocretin producing neurons in the hypothalamus, possibly via autoimmune mechanisms. Stimulants such as Modafinil or Amphetamine derivates are used to treat excessive daytime somnolence. Although Sodium Oxybate has been shown to effectively treat cataplexy, anti-depressants remain first line treatment in the UK.
Parasomnias are abnormal events occurring in association with sleep that are classified according to the sleep stage from which they occur. Some clinical features, such as timing of events during sleep, frequency of events and lifetime duration, are often helpful for the differential diagnosis of parasomnias.
Sleep-wake transition disorders occur during the transition between wakefulness and sleep and include rhythmic movement disorders such as head banging or body rocking, often seen in children. Episodes usually take place several times every night and may continue into adulthood. There have been discussions if these movements are a learnt behaviour and it is often difficult to treat.
Non-REM parasomnias occur from non-REM sleep, usually deep sleep and include sleep walking, sleep talking, confusional arousals and night terrors. Frequency of events varies but episodes occur most commonly in the first part of the night. Non-REM parasomnias are very common in childhood but may continue into adulthood. Safety aspects are the most important treatments to avoid injury to patient or bed-partner. Precipitants include sleep deprivation and stress. In more severe cases, medication such as long-acting Benzodiazepines or anti-depressant can be used. Non-REM parasomnias may be difficult to differentiate from nocturnal epilepsy.
REM sleep behavioural disorders (RBD) occur from REM sleep, often in the second half of the night. Onset is often after 50 years of age and there is an association with neurodegenerative disorders. RBD is characterised by loss of normal REM atonia associated with motor activity and sometimes dream enactment. RBD may be precipitated by anti-depressant medication and discontinuing medication will stop the events. Idiopathic forms are treated with long-acting Benzodiazepines or more rarely Melatonin.
It is sometimes possible to differentiate parasomnias on history alone, but often polysomnography is needed to clarify the diagnosis.
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