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For what seemed ages piled on ages, I lay there, frozen with the most awful fears, not daring to drag away my hand; yet ever thinking that if I could but stir it one single inch, the horrid spell would be broken. I knew not how this consciousness at last glided away from me; but waking in the morning, I shudderingly remembered it all, and for days and weeks and months afterwards I lost myself in confounding attempts to explain the mystery. -- Moby Dick, Chapter iv, by Herman Melville, 1851
(see Herman J. An Instance of Sleep Paralysis in Moby Dick. Sleep. 1997;20:577-9.) |
The "I" in the title is me. The "I" in the quote above is Ishmael, the narrator of Melville's Moby Dick. We both experienced what is known as "sleep paralysis." My first episode occurred many years ago, probably before I went to medical school. Since then I've had the experience three or four more times, a frequency of about once a decade.
Each time is terrifying. I suddenly am awake and aware of the bed and my situation, but realize I cannot move. It is not a dream; I desperately want to move but no muscles respond. I can breathe, but on at least one occasion my head was under the blanket, and I felt a dread of suffocation.
I remember thinking once, is this a nightmare? But it seemed real to me, and so it was. Each time I have struggled mightily to move. The time seemed brief, probably no more than a few minutes. Suddenly I 'wake up' and the spell is broken. I can sit, get out of bed, breathe easy. After a few more minutes, I go back to sleep. The paralysis has not recurred the same night nor, I am certain, twice in the same year.
Somehow, the first time it occurred, I knew the experience was probably normal and did not worry about it. But I didn't understand the phenomenon, or even know its name, until I came across an article in the Journal of the American Medical Association some years later; on the cover of the journal was Fuseli's famous painting The Nightmare (1781), a depiction of sleep paralysis as perceived in the 18th century. Inside was an article about my experience - sleep paralysis.
Over the years sleep paralysis has been well characterized, and is now known to be a normal event occurring at least once in about half the population. Sleep paralysis is one of the "parasomnias" ('events about sleep'). Parasomnias can be normal events (e.g., occasional sleep paralysis), or abnormal (e.g., sleep walking in adults). The following table shows some of the more common parasomnias, along with possible treatment (when needed).
Type of Parasomnia |
Sleep Stage |
Clinical Features |
Treatment (when needed) |
| Sleep paralysis | REM* | Awakening from sleep and feeling paralyzed; can be isolated event (normal), familial (rare), or part of narcolepsy (common) | Clonazepam (Klonopin) 1-2 mgm at bedtime |
| Bruxism | Non-REM Stages 1 & 2 | Grinding of teeth while sleeping | Dental checkup; bite-guard |
| Sleep walking | Non-REM Stage 3 | Up to 15% of normal children; <1% of adults (abnormal) | Create a safe environment for sleep walker; Non-drug therapy: psychotherapy, hypnosis; Drug therapy: Sinemet (carbidopa and levodopa); Mirapex (pramipexole); Benzodiazepines: clonazepam (Klonopin), 0.25 to 1.5 mg an hour before sleep; alprazolam (Xanax) and diazepam (Valium) are also used |
| Sleep eating | Non-REM Stage 3 | About 2/3 of patients are female. Eat while sleep walking, often high calorie foods (cookies, cake, starches) and sometimes bizarre foods (e.g., cat food, salt and pepper bread sandwich). | Same as sleep walking |
| Night terrors | Non-REM Stage 3 | Sudden, loud, terrified screaming accompanied by fast breathing and/or fast heart beat, sweating. Seen in 1-4% of children, occasionally in adults. There is poor to no recall once the subject is awake (in contrast to nightmares) | Psychotherapy; benzodiazepines (e.g., Klonopin) |
| Nightmares | REM Sleep | Universal; subject may wake up; excellent recall | None usually; rarely benzodiazepines |
| REM sleep behavior disorder | REM sleep | Usually in older men: the acting out of action-packed, often violent dreams. May manifest as yelling, swearing, gesturing, grabbing, punching, kicking, jumping out of bed and running behavior. Half the cases are associated with a neurologic disorder, such as Parkinson's disease and stroke; affected persons are usually mild mannered during the day | clonazepam (Klonopin) 0.5 - 1.5 mg before bedtime |
| Restless leg syndrome (RLS)/Periodic Leg Movements of Sleep (PLMS) | Non-REM sleep; diagnosed by sleep EMG** | More common in older people; can be due to organic illness (e.g.,
iron deficiency, renal failure). RLS/PLMS may be associated with arousals and
excessive daytime sleepiness |
Klonopin |
*REM = rapid eye movement
**EMG=electromyogram, which tracks muscle movements. Only PLMS is diagnosed with an EMG. Diagnosis of RLS is made solely by the patient's history. See "My husband kicks me during sleep." .
Parasomnias are a heterogeneous group, all characterized by some change in mentation during sleep. The medical term is 'disorder of arousal', meaning the brain is changing from one phase to another, and with it the subject has an unusual or bizarre or frightening experience.
While the table above is orderly in its categories, in fact a person can have overlap of one or more parasomnias (e.g., night terror and sleep walking). There is also overlap of some parasomnias with organic illness (e.g., Parkinson's disease, cerebrovascular disease [stroke]) and with psychiatric illnesses. And of course, in many cases a parasomnia can be considered normal (e.g., sleep walking in children, isolated sleep paralysis).
The American neurologist Weir Mitchell first reported sleep paralysis in 1876, in two healthy white males (Mitchell, SW. Some disorders of sleep, Am. J Med Sci. 1890;109-127.)
Since then numerous terms have been used to describe the experience:
- sleep numbness
- nocturnal hemiplegia
- nocturnal paralysis
- cataplexy of awakening
- postchalastic fits
-
"Old Hag"
In addition to its occurrence in healthy people, sleep paralysis is also commonly seen in certain sleep disorders, especially narcolepsy. The condition has clearly fascinated sleep specialists over the years, and knowledge has accumulated. We now know the following:
To be continued...
