Hypnic Jerk – What is a Hypnic Jerk ?

Various names have been associated with hypnic jerk; the hypnagogic jerk, the night start or the sleep start. Some disorders of the brain causes sudden, involuntary muscle spams or muscle twitching. These

muscle spams

occurs without any particular pattern or rhythm and are called

myoclonic twitch

. These myoclonic twitch are common during hypnagogia when the person is just about to fall asleep.

What causes hypnagogic jerk ?

Remember the “jump” felt when we are startled or surprised. The hypnagogic jerks are the same and is often accompanied by a falling sensation.

    • Irregularities in the sleeping schedules cause these hypnagogic jerks.
    • The neurological reason is yet to be studied and understood.
    • Two theories are associated with hypnagogic jerks –


    • First

      , sudden slowing down of the heart beat and the rate of breathing may cause muscular transition naturally.

    • Second

      , as we fall asleep, our muscles tend to cease working and relax.

  • This may signal the brain that we are falling through air and we thrash our limbs (attempting to catch something) or turn ourselves upright.

How often does these occur ?

  • We may experience hypnagogic jerks 1-2 times in a night and up to 5 times in a month.
  • During normal sleep, we may experience regular but less intense hypnagogic jerks. But, if this becomes more severe and occurs for more number of times, it is named as periodic limb movement.
  • These events occur during sleep and the patient is often observed sleeping through the events.
  • If you are deprived of sleep and still fighting sleep, then hypnic jerks will be more frequent and more intense.
  • Generally, this occurs in people who are deprived of sleep for more than 24 hours.
  • Even people who have woke up from insufficient sleep are prone to suffer from hypnagogic jerks.

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