The myoclonic epilepsies of childhood

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A RELATIVELY important proportion of the epilepsies that occur during the first 5 to 8 years of life include frequently repeated seizures characterized clinically by brief muscular contraction or loss of tone, often resulting in multiple daily falls. Many such epilepsies are associated with variable degrees of neuromental dysfunction and show little sensitivity to antiepileptic drugs.

The electroencephalograhic (EEG) concomitants of such seizure disorders include interictal bilateral, but not necessarily symmetrical, spike-wave complexes, either slow (< 2.5 Hz) or fast (≥ 2.5 Hz), variably associated with other paroxysmal or nonparoxysmal abnormalities such as slow background rhythm, or focal or multifocal spikes or sharp waves. Some investigators term all such cases myoclonic epilepsy,1 regardless of the type of EEG paroxysms and of the exact electroclinical type of seizures. Currently, most writers2–6 prefer to subdivide this large group into at least two broad subgroups. The first subgroup features predominantly tonic and atonic seizures7 usually associated with interictal slow spike-waves,8–10 and corresponds roughly to the Lennox-Gastaut syndrome.5,6,9,11,12 The second subgroup comprises primarily true myoclonic seizures,13–16 most commonly featuring ictal or interictal fast spike-wave complexes on the EEG, and corresponds to the myoclonic epilepsies proper. Distinctions between the two subgroups, however, are not sharply defined, since several types of attacks, of both myoclonic and atonic-tonic nature, may occur in the same patient, and the EEG may include both fast and slow spike-wave activity, resulting in a number of intermediate and unclassifiable cases.2

The nosological confusion is increased by the fact that. . .



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