Hypnic jerk

What is a Hypnic jerk?

Hypnic jerks are a sudden jumping sensation of the body which occurs during the transition between wakefulness and sleep. It is not entirely clear why they occur. However, they are a normal occurrence with most people experiencing them at some time in their lives.

It has been suggested that the brain misinterprets muscle relaxation as falling, and so, stimulates muscle activity in response.  Hypnic jerks usually occur during waking up or falling asleep. Patients will only notice these if they wake from their sleep and can describe the episodes as a ‘jolt’ or ‘sudden falling’. They may also be associated with vivid dreams, or more rarely auditory or visual hallucinations. Hypnic jerks can also be known as ‘myoclonus’ or ‘hypnagogic’ jerks.

Who experiences Hypnic Jerks?

At least 80% of people have reported having experienced Hypnic Jerks, with up to 10% having these every night. These can occur more frequently when people are over-tired or in an uncomfortable position.

Investigations

If patients describe their experience of Hypnic Jerks as explained above, no tests are required. If the patient has lots of jerks during normal wakefulness or if the jerks are happening continuously at night, they will need further assessment.