Introduction to Parasomnias

by Roy Strowd, MD

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    00:01 Let's start with a definition. What are parasomnias? Well, these are a pattern of sleep disorders marked by unusual actions, activities, or physiologic events that occur during sleep or that sleep-wake transition. In general, when we classify the parasomnias, we can divide them into those that occur during non-rapid eye movement sleep or the non-REM sleep arousal disorders and those that occur during rapid eye movement sleep or REM sleep arousal disorders. Let's start by reviewing some of the non-REM parasomnias that includes sleep walking, sleep terrors, sleep-related eating disorder, confusional arousal, and sleep-related abnormal sexual behavior.

    00:49 When we think about the REM sleep parasomnias, that includes REM behavior disorder which is the most important and one I'd like for you to understand including what was present in our case and nightmare disorder. So let's start by reviewing the normal sleep cycle and think about when and why the non-REM and REM parasomnias may occur. Here, we're looking at the typical sleep-wake cycle, from awake to N1, N2 and deep sleep and then REM sleep. In general, the parasomnias occur as a result of a dissociation between consciousness in wakefulness and in non-REM and REM sleep. These are disorders that arise from the sleep-wake boundary. There is discontrol of wakefulness and the stages of sleep and so wakefulness begins to encroach during these periods of sleep. In the non-REM sleep-related parasomnias, we see an admixture of wakefulness in to non-REM sleep, most often during that deep slow wave sleep. In general, when we're sleeping, our non-REM sleep is earlier in the night and so we often see non-REM parasomnias occurring earlier at night. And during these conditions, patients are very very deep in sleep and so they become very hard to arouse during the episode.

    02:09 We see increased slow wave sleep in non-REM parasomnias. Patients are difficult to arouse and there may be the potential for motor capacity. Again, during non-REM sleep, patients have normal tone, they are not atonic and so we can see movement and other activities occur during the non-REM parasomnias. Some of the factors that contribute to non-REM parasomnias include genetic predisposition, conditions like stress, sleep deprivation, fever, other physical and psychosocial emotional stressors that can precipitate these events, as well as substances including alcohol and others. When we think about the REM-related parasomnias, these occur as a result of an admixture of wakefulness during REM sleep. So patients are waking up during that REM sleep and this is believed to result from degeneration of cells involved in normal REM sleep pathways. The majority of our REM sleep occurs later in the night. So in general, the REM sleep disorders occur later at night and patients may be easy to arouse during these episodes owing from the fact that this is occurring during that REM dream type phase of sleep. How about the epidemiology and whom do we see non-REM and REM parasomnias? Well, for the non-REM sleep disorders, this is more common in the younger demographics in children. We tend to see these conditions in children, in many, though not all will grow out of these conditions as they age over time. Our REM sleep disorders are more common in older demographics as individuals aged or an association with neurodegenerative conditions that occur during the aging process.

    03:55 And they more commonly affect men. Sleep-related eating disorder is more common amongst women and REM sleep behavior disorder has a high prevalence in those who may go on to develop Parkinson's disease. What about the diagnostic approach to parasomnias? When we think about our work-up for patients, we're using the history, features that occur with these episodes and potentially our polysomnography to evaluate these patients. When we think about the non-REM parasomnias, non-REM parasomnias often are diagnosed by taking a detailed history. We look at when these episodes happen during night whether patients are aware or able to be aroused and what things look like in the morning whether they remember or recall these events or not. In terms of making a clinical diagnosis, it's very important to understand when the events occur at night, non-REM sleep disorders occur earlier in the night and tend to be less common later in the night.

    04:56 Patients are very difficult to arouse owing to these occurring during deep slow wave sleep and often patients will not have recollection. The polysomnography can be used in the evaluation of these disorders but is really used to evaluate alternative explanations and is not a confirmatory test for a specific non-REM parasomnia diagnosis. When there are suspicion of comorbid OSA, polysomnography can be quite helpful and it is required for a definitive diagnosis of REM behavior disorder.

    About the Lecture

    The lecture Introduction to Parasomnias by Roy Strowd, MD is from the course Sleep Disorders​.

    Included Quiz Questions

    1. Parasomnias
    2. Circadian rhythm sleep–wake cycle disorders
    3. Hypersomnias
    4. Dyssomnias
    5. Somnambulism
    1. NREM
    2. REM
    3. Initiation
    4. Awake
    5. None
    1. NREM vs. REM
    2. Hypersomnolent vs. hyposomnolent
    3. Advanced vs. delayed
    4. Physiologic vs. psychologic
    5. Sleepwalking vs. sleep terrors
    1. Polysomnography
    2. EEG
    3. Multiple sleep latency test
    4. Functional MRI testing
    5. Lumbar puncture

    Author of lecture Introduction to Parasomnias

     Roy Strowd, MD

    Roy Strowd, MD

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