Hypnic jerks, also known as hypnagogic jerks or the phantom twitches of sleep, are a common phenomenon in which people experience jolts when dozing off or waking up. Also called sleep myoclonus, they most often occur during these sleep transitions. Most people experience them one or more times throughout their lives.
Though between 60 and 70% of people of both sexes experience them, it remains unclear what causes hypnic jerks, though researchers have a number of theories. The most popular relates the phenomenon to sleepwalking and dreaming. In this view, hypnic jerks are a product of automatic muscle movement during a period when the brain is over-aroused. This theory suggests that hypnic jerks are similar to the spontaneous muscle movements associated with sleepwalking.
The most common symptom of hypnic jerks is a sudden jerking of a body part, such as an arm or leg, just as the person is drifting off to sleep. When hypnic jerks occur here, many people experience a sensation of falling that can be frightening. Less commonly, hypnic jerks cause rapid heart rate and breathing, sweating, or hallucinations. Some people hear an audible "snap" or see a flash of light during an episode. Hypnic jerks can be disturbing, especially if they interfere with sleep.
There does not appear to be a clear gender or age relationship to hypnic jerks. Factors that increase the risk include mental or physical stress, excessive caffeine or other stimulants, and exercise too close to bedtime. Fatigue and irregular or poor sleep habits are other possible contributors. Research also shows that hypnic jerks are more common in people with Parkinson's disease, although this is an area that needs more research. They're also more frequent in people who get migraines and in children with neurological disorders.
The diagnosis of hypnic jerks is often made through history and physical exam. However, doctors may want to rule out medical causes, such as seizures, movement disorders, and other sleep disorders. To do so, they may perform an EEG (electroencephalogram), a test that looks at brain waves and electrical activity in the brain.
In most cases, treatment isn't required unless hypnic jerks are part of a more complex sleep disorder. If hypnic jerks become too frequent or interfere with healthy sleep, lifestyle changes such as stress management may reduce their frequency. Although not commonly prescribed, some medications may offer benefits in cases where the symptoms are frequent or persistent and other treatments have failed.
Although treatment, other than lifestyle changes, is often not necessary, some doctors may prescribe valproic acid, a medication used to treat seizures, or clonazepam to reduce the frequency of the jerks. In many cases, no medication is necessary and the doctor will simply take care to reassure their patient that hypnic jerks are not dangerous.
The best way to reduce the risk of hypnic jerks is to practice good sleep hygiene and get enough quality sleep. Exercise is a healthy habit, but exercising within a few hours of bedtime can sometimes bring on the spasms. Also, cut back on caffeine and avoid consuming caffeine after the early afternoon to ensure it's not still in your system at bedtime.
Since hypnic jerks are linked with overarousal of the nervous system, people can usually prevent them, or at least reduce their frequency, with changes in lifestyle. Stress management plays a key role, as does reducing activity and stressors before bedtime. Some people only have one or a few hypnic jerks over a lifetime, while they may be more frequent in people who are anxious or stressed.
There are no known complications of hypnic jerks, once seizures are ruled out. However, some people are disturbed by them and need confirmation they're not caused by a more serious condition. That's why it's important to see a healthcare provider for reassurance. Sometimes knowing that hypnic jerks are benign will reduce anxiety enough to decrease their frequency.
The long-term prognosis for hypnic jerks is excellent since it's not a disease or illness but a common phenomenon that many people experience at some point in their life. Although some people experience them on and off forever, they are benign and typically don't require treatment or long-term follow-up.
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