This body movement is what doctors and scientists call a hypnic (or hypnagogic) or myoclonic jerk. It's also known as a "sleep start," and it can literally startle you out of falling asleep. This type of feeling is normal, and it can happen before people enter the deeper stages of sleep.
“If a person has a less common presentation of frequent and serial hypnic jerks occurring back-to-back instead of a solitary contraction, this is more likely to cause insomnia of significance or could be another condition, such as seizures, that should at least be evaluated by a health care provider.”
While these muscle spasms are not 100 percent understood, they are a common occurrence. As many as 70 percent of people experience this jerking sensation that happens when the body transitions from wakefulness to sleep. They usually only happen once, maybe twice, and they may last a half second or less.
These are completely normal and aren't the same as a myoclonic seizure. They are: Hypnic jerks: If you've ever had a sudden muscle twitch or spasm right as you were falling asleep, that was a hypnic jerk (the name comes from “hypnos,” the Greek word for “sleep”).
Finally, from a nutritional perspective, it has been suggested, albeit anecdotally, that deficiencies in magnesium, calcium and/or iron can also increase the chances of experiencing a spontaneous hypnic jerk.
Muscle twitching is a common symptom of anxiety. Those with chronic and severe anxiety may experience muscle twitching more often. Causes of muscle twitching vary, from adrenaline to vitamin loss, and more. The twitching itself is not dangerous, but is a sign that anxiety needs to be treated.
Sleep myoclonus causes involuntary muscle twitches during sleep or when a person falls asleep. In some cases, sleep myoclonus occurs on its own without an identifiable cause. Sleep myoclonus can also develop as a result of a sleep disorder or a neurological disorder.
Physiologic myoclonus involves quick muscle twitches followed by relaxation. Examples are hiccups and the jerks or “sleep starts” that some people experience while drifting off to sleep. This form occurs in healthy people, causes no difficulties, and does not require medical treatment.
And if they happen to you frequently, you might worry whether they're normal. "Fasciculations, which are random, involuntary muscle twitches, are extremely common," says Dr. William Ondo, a neurologist who specializes in movement disorders at Houston Methodist. "About 70% of people report experiencing them."
Opiates such as morphine, heroin and methadone have been reported to cause these jerks with regular frequency along with sudden jerking and waking during the night's sleep.
Myoclonus refers to a quick jerking movement that you can't control. Hiccups are a form of myoclonus, as are the sudden jerks or "sleep starts" that you may feel just before falling asleep. These forms of myoclonus occur in healthy people and usually aren't serious.
The most common anticonvulsants used for myoclonus are levetiracetam (Keppra, Elepsia XR, Spritam), valproic acid, zonisamide (Zonegran, Zonisade) and primidone (Mysoline). Piracetam is another anticonvulsant that's been found to be effective, but it's not available in the United States.
A common symptom among veterans is nocturnal myoclonus, a sudden spasm of the whole body while sleeping or drifting off into sleep. It lasts for about a fraction of a second, but may occur several times in a single night. Often people with PTSD will sleep through such a spasm, but their partner may not.
Myoclonus is sudden muscle spasms that you can't control. They can be normal -- a hiccup or a "sleep start" when you're falling asleep, for example -- or they may be a sign of a serious health condition such as multiple sclerosis, dementia, or Parkinson's disease.
Myoclonus is an uncontrollable muscle movement that's sudden and brief. This can happen for a wide range of reasons. Many causes are normal and harmless, but myoclonus can also be a symptom of serious nervous system conditions.
Ataxia. Ataxia is a degenerative disorder affecting the brain, brainstem or spinal cord. This can result in clumsiness, inaccuracy, instability, imbalance, tremor or a lack of coordination while performing voluntary movements. Movements are not smooth and may appear disjointed or jerky.
A hypnagogic jerk is an involuntary phenomenon that causes brief muscle contractions as you're falling asleep. Experts aren't sure what exactly causes these sudden jerks or jolts to happen, but they may be affected by factors like stress, anxiety, sleep deprivation, or evening caffeine intake.
Physically, hypnic jerks resemble the "jump" experienced by a person when startled, sometimes accompanied by a falling sensation. Hypnic jerks are associated with a rapid heartbeat, quickened breathing, sweat, and sometimes "a peculiar sensory feeling of 'shock' or 'falling into the void'".
Are there any other signs or symptoms of hypnic jerks? Apart from the obvious muscle twitches, you may also experience increased heartbeat, rapid breathing, sweating, clammy skin, and a falling sensation.
Jerky body movement is a condition in which a person makes fast movements that they cannot control and that have no purpose. These movements interrupt the person's normal movement or posture.
The same phenomenon is called a hypnic jerk if it occurs upon awakening. For example, you might believe that you were falling. A leg movement may incite a fragmentary dream image that you were perhaps kicking a soccer ball.
Symptoms of Paradoxical Insomnia
People with paradoxical insomnia report feeling aware of their surroundings at night and sleeping for only a few hours each night, if at all, despite objectively sleeping for long enough to avoid sleep deprivation symptoms.
If muscles twitch or jerk repeatedly, this is known as 'clonus', for example when a foot taps repetitively on the floor. Some people with MS experience other spasms - sudden involuntary movements that can make the arms or legs move in different ways. These can occur even without the muscle being stretched.
Sleep-related rhythmic movement disorder (SRMD) is a condition characterized by repetitive, rhythmic movements occurring when a person is drowsy or during sleep. These movements are most often body rocking, where a person moves their entire body, headbanging, or head rolling.