Hypnic jerk
A common, benign muscle twitch at sleep onset.
A hypnic jerk is a brief, sudden involuntary muscle contraction that occurs at sleep onset, often causing a person to jump and briefly awaken. It is a form of myoclonus and is considered a common physiological phenomenon, with around 70% of people experiencing it at least once. While mostly benign, frequent and severe hypnic jerks can contribute to sleep-onset insomnia.
Quick Facts
- Field
- Sleep medicine
- Risks
- Irregular sleep schedule
- anxiety
- excessive stimulant consumption
- stress
- smoking
- antidepressants
- Diagnosis
- Based on symptoms
- Treatment
- Medication, reducing stimulant consumption
- Medication
- Clonazepam
Facts from the source article.
Causes
The American Academy of Sleep Medicine notes a wide range of potential causes, including anxiety, stimulants such as caffeine and nicotine, stress, and strenuous activities in the evening. Fatigue or sleep deprivation may also facilitate hypnic jerks, and antidepressant usage has been identified as a potential risk factor. However, most hypnic jerks occur essentially at random in healthy people. Repeated, intensifying twitches can cause anxiety in some individuals and disrupt sleep onset. A hypnic jerk occurs during the non-rapid eye movement sleep cycle and is an abrupt muscle action flexing movement, generalized or partial and asymmetric, which may cause arousal with an illusion of falling. Hypnic jerks are more frequent in childhood, with 4 to 7 per hour in the age range from 8 to 12 years old, decreasing to 1 or 2 per hour by 65 to 80 years old. The causes remain unclear and are still being studied; none of the several proposed theories has been fully accepted. One hypothesis suggests the jerk is a reflex initiated in response to normal bodily events during the lead-up to sleep, such as a decrease in blood pressure and muscle relaxation. Another theory proposes that the body mistakes the sense of relaxation as a sign of falling, causing a jerk to wake the sleeper. A researcher at the University of Colorado suggested it could be an archaic reflex to the brain's misinterpretation of muscle relaxation as a signal that a sleeping primate is falling out of a tree, possibly having selective value by prompting readjustment of sleeping position, but evidence is lacking.
Diagnosis
Hypnic jerks are often mistaken for other sleep-related movements, including restless legs syndrome, periodic limb movement disorder, hypnagogic foot tremor, rhythmic movement disorder, and hereditary or essential startle syndrome. They can be distinguished because hypnic jerks arise only at sleep onset and lack rhythmicity or periodicity in movements and EMG bursts. They may also be confused with myoclonic seizure, but differ in that hypnic jerks occur only at sleep onset, the EEG is normal and constant, and there are no tongue bites, urinary incontinence, or postictal confusion. In epilepsy monitoring, the absence of a preceding spike discharge and the occurrence only at sleep onset help differentiate hypnic jerks from epileptic myoclonus.
Treatment
Lifestyle changes like cutting back on stimulants such as nicotine or caffeine and steering clear of strenuous exercise before bed can lessen hypnic jerks. For some, a low dose of clonazepam at night may gradually stop the twitches. Although antidepressants are a known risk factor, combining them with clonazepam might help those who have both depression and hypnic jerks. A fixation on these jerks can raise anxiety and fatigue, which then makes the jerks more likely, forming a self-reinforcing cycle.
Frequently Asked Questions
How is Hypnic jerk treated?
Treatment of Hypnic jerk includes Medication and reducing stimulant consumption.
How is Hypnic jerk diagnosed?
Diagnosis of Hypnic jerk is based on Based on symptoms.
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