Muscle contractions in the form of "jerks" or twitches. In sleep-related (nocturnal) myoclonus, the jerks are primarily of the flexor groups in the lower extremities and have a characteristic frequency of 20-40 seconds.
A single spasm or twitching of a muscle. Myoclonus can be a single event (twitch) or repeated events. Myoclonus can be a normal event (the jerks that occur when we fall asleep) or an abnormal event (those that occur while awake, or those associated with seizures or mitochondrial diseases). Clonus is the repeated spasms of muscles, due to a seizure or increased muscle tone.
shocklike contractions of a portion of a muscle or an entire muscle or a group of muscles. The term ‘myoclonus' is applied to a brief, shock-like muscular contraction which may be confined to a single muscle or may involve many muscles, either successively or simultaneously. Often, contractions may occur symmetrically in muscles on the opposite sides of the body. The contraction may be too slight to cause movement or can cause such violent movement as to throw the person to the ground. The contraction does not affect groups of muscles which are normally synergistically associated, nor does it usually affect mutually antagonistic muscles.
myo-klonus Clonic spasm or twitching of a muscle or group of muscles. Nocturnal Myoclonus--frequently repeated muscular jerks occurring at the moment of dropping off to sleep. Similar jerks that awaken a sleeper occur occasionally in all normal persons. Palatal myoclonus--rhythmic contractions of the soft palat, the facial muscles and the diaphragm, related to lesions of the olivocerebellar pathways. Term: Definition: Description: . .
An involunatry, lightning-like muscle contraction or jerk that is marked enough to move a joint. Only one limb may be involved or the whold body may jerk as though suddenly startled. This condition is seen in a variety of illnesses, but is also a normal phenomenon when people are falling asleep. Attempts to control abnormal myoclonus usually focus on influencing the sertonergic system whti various agents.
Muscle contractions in the form of abrupt "jerks" or twitches generally lasting less than 100 milliseconds. The term should not be applied to the periodic leg movements of sleep that characteristically have a duration of 0.5 - 5 seconds.
Sudden, involuntary jerking of a muscle or group of muscles. Myoclonic twitches or jerks usually are caused by sudden muscle contractions, called positive myoclonus, or by muscle relaxation, called negative myoclonus. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Myoclonus sometimes occurs in response to an external event or when a person attempts to make a movement. The twitching cannot be controlled by the person experiencing it.
Very brief, involuntary, random muscular contractions. Myoclus can occur spontaneously at rest, in response to sensory stimuli, or with voluntary movements. Rhythmic or arrhyhthmic series of brief, shock-like (unidirectional) contractions of a group of muscles.
Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign (as opposed to symptom) and, generally, is not a diagnosis of a disease. The myoclonic twitches or jerks are usually caused by sudden muscle contractions; they also can result from brief lapses of contraction.