Myoclonus and Myoclonus-Dystonias

Myoclonus is characterized by rapid muscle jerks, while dystonia is defined as sustained twisting and repetitive movements, resulting in abnormal postures. In myoclonus dystonia (M-D), a predominantly myoclonic syndrome is combined with dystonic features. Linkage of autosomal dominantly inherited M-D is demonstrated to a locus on chromosome 7q, designated DYTll, followed by the recent identification of mutations in the 8-sarcoglycan gene (SGCE). However, SGCE clearly represents the major M-D gene. The function of its encoded protein, e-sarcoglycan, is largely unknown. It is a member of the sarcoglycan family, usually involved in muscular dystrophies, while M-D is a non degenerative disorder of the central nervous system. The drugs tested without any good effect on the involuntary movements are-amphetamine, heroin, carbamazepine, propranolol, chlorazepate, and haloperidol. Finally, neuro stimulation of the ventral intermediate thalamic nucleus is shown to be a safe and efficacious treatment in a patient with medically intractable and progressing M-D.