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One or a series of shock-like contractions of a group of muscles, of variable regularity, synchrony, and symmetry, generally due to a central nervous system lesion. [myo- + G. klonos, tumult]
- benign infantile m. a seizure disorder of infancy in which myoclonic movements occur in the neck, trunk, and extremities; the EEG is normal, and seizures do not persist beyond 2 years of age. SYN: benign m. of infancy.
- m. multiplex an ill-defined disorder marked by rapid and widespread muscle contractions. SYN: paramyoclonus multiplex, polyclonia, polymyoclonus.
- palatal m. rhythmic contractions of the soft palate, the facial muscles, and the diaphragm, related to lesions of the olivocerebellar pathways. SEE ALSO: palatal nystagmus.
- stimulus sensitive m. m. induced by a variety of stimuli, e.g., talking, calculation, loud noises, tapping, etc.
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my·oc·lo·nus .mī-'äk-lə-nəs n irregular involuntary contraction of a muscle usu. resulting from functional disorder of controlling motor neurons also a condition characterized by myoclonus
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n.
a sudden spasm of the muscles. Occasional myoclonic jerks occur between seizures in patients with idiopathic epilepsy, and myoclonus is a major feature of some progressive neurological illnesses with extensive degeneration of the brain cells (including the spongiform encephalopathy). Myoclonic jerks on falling asleep (nocturnal myoclonus) occur in normal individuals.
• myoclonic adj.
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my·oc·lo·nus (mi-okґlo-nəs) [myo- + clonus] shocklike contractions of a portion of a muscle, an entire muscle, or a group of muscles, restricted to one area of the body or appearing synchronously or asynchronously in several areas. It may be part of a disease process (e.g., epileptic or post-anoxic myoclonus) or be a normal physiological response (e.g., nocturnal myoclonus). myoclonic adjMedical dictionary. 2011.