You probably know this experience: you slide gently into sleep and you even begin to dream when suddenly you feel like falling into a void or something strikes you, and you awaken with a start.
Scientists have studied this very common phenomenon and have given it a name: myoclonus of sleep or hypnagogic myoclonus. This name intersects the following phenomena:
- We begin to fall asleep when, suddenly, our body tensens as if we had missed a step or had slipped on a sidewalk.
- We are sitting in our office, focused on our task, when one of our eyelids begins to start moving without control.
One is seized with an irrepressible hiccup that one can only calm by drinking upside down in a glass or by breathing in a paper bag.
These jerks are so many myoclonic spasms, in other words involuntary muscle spasms that last a short time. They are due to an abrupt contraction, a muscle twitch or relaxation that follows a contraction of the muscles. They can involve the entire body or only a muscle group (usually the lower limbs). Some researchers think they would occur when the individual suddenly falls into a deep sleep without going through the different stages.
This is called "paradoxical sleep". The brain thinks that the subject is dying and, in panic, sends an impulse into the body that causes the awakening. It seems that 60 to 70% of us are experiencing these drowsiness drops from time to time.
Can we say it is sleep disorder?
Not really, because these hypnic shocks, another name for the myoclonus of sleep, are a normal phenomenon and generally disturb the person who sleeps next door than the sleeper concerned. It is just an illusion of the brain that thinks one risks to die and sends a discharge that moves the limbs, often the legs. These bursts occur when the person falls directly into the deep sleep (paradoxical sleep) without going through the different stages.
The phenomenon may affect the whole body or a particular limb, and may be related to stress, fatigue, or alcohol consumption.
The myoclonus of sleep is not to be confused with the syndrome of the legs without rest which, constitutes a sleep disorder.
These sensations of tingling and tingling that give an irrepressible desire to move the legs concern 8.5% of the population in France, especially women. It is a chronic neurological disease without severity but whose symptoms increase with age, and often intervene during sleep.
The quality of sleep is impaired and somnolence can be felt during the day, with all that lack of sleep can generate: difficult concentration, memory problems, depression, irritability.
In case of regular shaking, should we worry?
Check with your doctor if the phenomenon seems to take too much and is accompanied by unexplained insomnia. A polygraph can be used to remove any doubt. This examination allows to observe the respiration of the sleeper by means of sensors, and is performed at home or in the hospital. Diagnosis may reveal epileptic myoclonus in some cases.
Further examinations are sometimes necessary because sleep myoclonus may be related to a more serious dysfunction of the nervous system: Alzheimer's, Parkinson's, Multiple Sclerosis