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Hypnic jerks are a sudden jumping sensation of the body which occurs during the transition between wakefulness and sleep.
Hypnic jerks are also known as myoclonus or hypnagogic jerks. They are a normal phenomenon, and most people will experience them at some time in their lives. They occur as the patient is falling asleep or waking up. It is not entirely clear why they occur, but it may be that the brain misinterprets muscle relaxation as falling, and hence induces muscle activity.
Patients describe hypnic jerks as a ‘jolt’ or ‘sudden falling’. They are only noticed if they wake the patient from sleep. They may be accompanied by vivid dreams, or more rarely auditory or visual hallucinations.
Who gets them?
At least 80% of people report having experienced hypnic jerks. It is estimated that up to 10% of people will have them on a nightly basis. They are thought to occur more frequently if the patient is over-tired or in an uncomfortable position.
No tests are required if they fit the description above. If the patient has lots of jerks during normal wakefulness, or if the jerks are happening continuously at night; they will need further assessment.
No treatment is usually required. Attention to ensuring adequate rest and a comfortable sleeping position may lessen their frequency.