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Epilepsies

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Epilepsies with predominantly myoclonic seizures in childhood and adolescence: diagnostic steps Volume 13, issue 3, Juillet - Août - Septembre 2001

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Author
Service de Neurologie Pédiatrique et des Maladies Métaboliques, CHU Robert-Debré (AP-HP), Paris, France

Myoclonic seizures are a common feature of many types of epilepsy at all ages and are, therefore, a nonspecific manifestation. A diagnostically useful feature of myoclonic jerks is their frequent saccadic character with a 3-Hz rate of repetition. Syndromes in which myoclonic attacks are the exclusive or predominant type of seizure are different in outlook and therapy from the Lennox-Gastaut syndrome. At onset of the epilepsy, a precise syndromic diagnosis may prove to be particularly difficult. However, a precise description of the clinical phenomena and the use of polygraphy and/or video EEG recordings allow the recognition of the appropriate clinical spectrum and avoid therapeutic errors. We discuss a diagnostic approach for epilepsies with myoclonic seizures (benign myoclonic epilepsy of infancy; Dravet syndrome; epilepsy with myoclonic-astatic seizures; epilepsy with myoclonic absences) based on age at onset, EEG features and above all precise determination of other seizure types that frequently accompany myoclonic attacks. Associated seizures are critical in the classification scheme of the myoclonic epilepsies.