True myoclonic epilepsy in childhood.

The term 'myoclonic epilepsy' is used in adults to describe a form of epilepsy in which a sudden, involuntary, and momentary contraction occurs in a single muscle or muscle group, often without apparent loss of consciousness. Such attacks may occur in isolation, or as part of the pattern of epilepsy in patients experiencing grand mal or other forms of epilepsy. A recent authoritative review of the subject in adults is given by Aigner and Mulder (1960). It is generally agreed that myoclonic epilepsy does occur in childhood, but confusion has arisen on account of differing descriptions and nomenclature. Early writers such as Unverricht (1891) and Lundborg (1903) used the term myoclonus to denote any involuntary movement or muscle jerk occurring during a degenerative neurological illness, and considered myoclonus to be a symptom of underlying organic disease. Later the term 'myoclonic' was used by many authors to describe the involuntary muscle jerks that occur as subsidiary phenomena in the intervals between grand mal attacks in patients with major epilepsy. Muskens (1909) described 'the common occurrence of single, sudden and often isolated convulsions (or regional jerks) with sudden adduction or abduction of one or both arms, or a sudden flexion of extension of the trunk'. He considered that these episodes occurred most often in intervals between grand mal attacks, or that they might precede the onset of grand mal by as much as several years. Hodskins and Yakovlev (1930) found myoclonus in 10-15% of a mixed age-group of 300 cases of all forms of epilepsy, and commented upon a frequency of a positive family history of epilepsy and a high incidence of cerebellar signs in patients showing myoclonus. Gastaut (1954) commented that myoclonus had become a somewhat neglected symptom in most books on epilepsy and deserved to be reinstated. Bridge (1949) recognized the occurrence of myoclonic epilepsy in children, though he considered this to be a very rare form of epilepsy in childhood.