Myoclonic encephalopathy of infants

Abstract

The intrusion of shock-like, muscular contractions may totally disorganize willed movements involving the affected muscle groups. If the contractions are frequent and violent the appearance may even suggest a cerebellar ataxia. But the persistence of the shock-like contractions when the affected part is at rest, and electroencephalographic evidence of a cerebral dysrhythmia related in its irregular timing to that of the involuntary muscular contractions, reveal the presence of myoclonic status. In most cases in which generalized myoclonic status is present as an isolated abnormality in a child, it proves to be a manifestation either of 'idiopathic epilepsy' or of the onset of a progressive cerebral degeneration. It is proposed to report six cases in which myoclonic status produced clinical appearances and took a course differing from any previously described and yet conforming to a consistent and distinctive pattern. The acute onset of myoclonic status (especially involving the extraocular muscles in an unusual manner) was unaccompanied by electroencephalographic evidence of cerebral discharges. This isolated motor disorder pursued a protracted but not progressive course.