Hypnagogic Sleep Paralysis Explained

Have you ever felt like you were awake but unable to move? You might have even felt afraid but could not call for help? This condition is called sleep paralysis. Sleep paralysis may leave you feeling frightened, especially if you also see or hear things that aren’t really there. Sleep paralysis may happen only once, or you may have it frequently — even several times a night.

The good news: sleep paralysis is not considered a dangerous health problem. Read on to find out more about sleep paralysis, its possible causes, and its treatment.

Hypnagogic or hypnopompic hallucinations are visual, tactile, auditory, or other sensory events, usually brief but occasionally prolonged, that occur at the transition from wakefulness to sleep (hypnagogic) or from sleep to wakefulness (hypnopompic).

The phenomenon is thought to have been first described by the Dutch physician Isbrand Van Diemerbroeck in 1664. The person may hear sounds that are not there and see visual hallucinations. These visual and auditory images are very vivid and may be bizarre or disturbing.

Usually it is part of the tetrad of narcolepsy that includes:

  • Excessive daytime sleepiness
  • Cataplexy
  • Hypnagogic hallucinations
  • Sleep paralysis.
  • This tetrad is rarely seen in children.

Is sleep paralysis a symptom of a serious problem?

Sleep researchers conclude that, in most cases, sleep paralysis is simply a sign that your body is not moving smoothly through the stages of sleep. Rarely is sleep paralysis linked to deep underlying psychiatric problems.

Over the centuries, symptoms of sleep paralysis have been described in many ways and often attributed to an “evil” presence: unseen night demons in ancient times, the old hag in Shakespeare’s Romeo and Juliet, and alien abductors.

Almost every culture throughout history has had stories of shadowy evil creatures that terrify helpless humans at night. People have long sought explanations for this mysterious sleep-time paralysis and the accompanying feelings of terror.

When does sleep paralysis usually occur?

Sleep paralysis usually occurs at one of two times. If it occurs while you are falling asleep, it’s called hypnagogic or predormital sleep paralysis. If it happens as you are waking up, it’s called hypnopompic or postdormital sleep paralysis.

What happens with hypnagogic sleep paralysis?

As you fall asleep, your body slowly relaxes. Usually you become less aware, so you do not notice the change. However, if you remain or become aware while falling asleep, you may notice that you cannot move or speak.

What happens with hypnopompic sleep paralysis?

During sleep, your body alternates between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. One cycle of REM and NREM sleep lasts about 90 minutes.

NREM sleep occurs first and takes up to 75% of your overall sleep time. During NREM sleep, your body relaxes and restores itself. At the end of NREM, your sleep shifts to REM. Your eyes move quickly and dreams occur, but the rest of your body remains very relaxed.

Your muscles are “turned off” during REM sleep. If you become aware before the REM cycle has finished, you may notice that you cannot move or speak.

Who develops sleep paralysis?

Up to as many as four out of every 10 people may have sleep paralysis. This common condition is often first noticed in the teen years. But men and women of any age can have it.

Sleep paralysis may run in families. Other factors that may be linked to sleep paralysis include:

  • a lack of sleep
  • a sleep schedule that changes
  • mental conditions such as stress or bipolar disorder
  • sleeping on the back
  • other sleep problems such as narcolepsy or nighttime leg cramps
  • use of certain medications
  • substance abuse

How is sleep paralysis treated?

Most people need no treatment for sleep paralysis. Treating any underlying conditions such as narcolepsy may help if you are anxious or unable to sleep well. These treatments may include the following:

  • improving sleep habits — such as making sure you get six to eight hours of sleep each night
  • using antidepressant medication to help regulate sleep cycles
  • treating any mental health problems that may contribute to sleep paralysis
  • treating any other sleep disorders, such as narcolepsy or leg cramps

Investigations

Blood tests and imaging are likely to be normal.
Referral to a special sleep laboratory may be required to diagnose narcolepsy.

Management

Tricyclic antidepressants hold back the dreaming state and may be beneficial. However, a Cochrane review was unimpressed by the evidence.

Musical hallucinations may be helped by the atypical antipsychotic quetiapine.
For the treatment of narcolepsy see the narcolepsy and cataplexy article.

Prognosis

If the patient has narcolepsy the prognosis is as for that disease. If not, reassurance is all that is required. If it is disturbing, tricyclic antidepressants may be used intermittently.

Source & More Info: patient.co.uk and Medicine Net

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