[Myoclonus and epilepsies in children].

The possible associations of myoclonic phenomena, progressive or non progressive encephalopathies and epileptic phenomena are reviewed with special emphasis on childhood. This leads to the following five groups of conditions: (1) myoclonus without encephalopathy and without epilepsy; (2) encephalopathies with non-epileptic myoclonus; (3) progressive encephalopathies with myoclonic seizures or epileptic syndromes (Progressive myoclonus epilepsies); (4) epileptic encephalopathies with myoclonic seizures; (5) myoclonic epilepsies. In the first group, which also includes physiological myoclonus, a more thorough description of "benign sleep myoclonus of newborn" and "benign myoclonus of early infancy" is given. Characteristic of group 2 are "Kinsbourne syndrome" and certain types of "Hyperekplexia" which pose interesting differential diagnosis problems with stimulus-sensitive epilepsies. In group 3, the concept of progressive encephalopathies is stressed, meaning that "Progressive Myoclonus Epilepsies" are always in fact progressive encephalopathies presenting with myoclonic types of seizures or epileptic syndromes among other neurologic and psychologic signs and symptoms. Major and rare causes are reviewed. The term major is applied to typical features or to frequency, whereas rare causes include not only those what are rarely seen, but also some myoclonic variants of diseases which usually have different symptoms. The fourth group refers to severe epilepsies, mainly in infancy and childhood, which lead to mental retardation irrespective of their cause. The assumption is that diffuse and persistent epileptic activity may interfere with normal development of the higher cerebral functions. "West syndrome" and "Lennox-Gastaut syndrome" are the more representative examples and may present with myoclonic type of seizures, but they are not dealt with in detail here. Group 5 comprises true myoclonic epilepsies, differentiating syndromes recognized as idiopathic, such as "benign myoclonic epilepsy of infancy" and "juvenile myoclonic epilepsy", from those which are cryptogenic and carry a more cautious prognosis--i.e.: "cryptogenic myoclonic and myoclono-astatic epilepsies" and "Severe myoclonic epilepsy of infancy". Finally other epileptic syndromes usually not considered as myoclonic epilepsies, but presenting sometimes myoclonic seizures, are mentioned.