Epilepsy with myoclonic absences

Among the epileptic syndromes that are defined mainly on the basis of a characteristic seizure type, epilepsy with myoclonic absences (EMA) stands out as a somewhat controversial entity. This is because the sound and evident clinical characteristics on which it was identified some 30 years ago have evolved, mostly as a consequence of changes in the practical management of epilepsies and to the description of myoclonic components in a variety of other generalised epilepsies with absences. Myoclonic absences (MA) are described as typical absences with sudden onset and offset that are associated with generalised spike and wave (SW) discharges on the ECG, with distinctive traits. Clinically, absences are associated with axial hypertonia (the subject usually bends forward and slightly raises their shoulders and arms), and jerks synchronous with the SW discharges. Neurophysiologically, axial hypertonia and rhythmic jerks may be recorded on polygraphic surface electromyogram leads in association with the typical SW discharges; as such, despite an ECG, the diagnosis may be missed in the absence of video documentation of the seizure and/or adequate polygraphy. MA need to be distinguished from absences with other types of prominent myoclonic accompaniment (perioral, eyelid, limbs).The prognosis of EMA remains variable. Modern therapeutic combinations, such as valproic acid and ethosuximide, or valproic acid and lamotrigine, are usually effective; however, in a proportion of patients, seizures are resistant to drug treatment. These patients may experience cognitive deterioration and, in some cases, evolution towards a more severe form of epilepsy, including the Lennox-Gastaut syndrome. The more benign cases usually present with MA as the only seizure type, while patients who experience other seizures, especially generalised tonic-clonic seizures, in association with MA may have a less favourable outcome.