Hereditary Essential Myoclonus

Abstract

MYOCLONUS is a rapid, brief contraction of one muscle or a group of muscles which may or may not result in observable movement at a joint. It is usually irregular and generalized in its temporal and spatial distribution. The muscle contractions are commonly arrhythmic, asynchronous, and asynergic. However, myoclonus is quite variable and it may be focal, regular, rhythmic, synchronous or synergic. The movements occur singly or at relatively low frequency. They can involve any muscle group but most commonly occur in proximal muscles of the limbs, and in the neck and trunk muscles.^1-3 Myoclonus has been described in normal individuals and in a variety of diseases including epilepsy, encephalitis, degenerative diseases, and toxic, anoxic, or metabolic encephalopathy. It can occur with lesions in the cerebral hemispheres, brain stem, cerebellum, or spinal cord.^1,3-5 There have been a number of descriptions, classifications, and discussions of the clinical appearance and