Atypical absences are epileptic seizures that occur in children with severe learning and neurologic disabilities of epileptic encephalopathies, mainly, Lennox-Gastaut syndrome. They are distinct from typical absences in that onset and termination is slow, impairment of consciousness is mild, and they are often associated with significant tone disturbances. The ictal EEG shows diffuse spike waves that are slower than the typical absence, usually between 1.5 and 2.5 Hz. Patients with atypical absences also suffer from concurrent tonic, atonic, and other types of epileptic seizures according to the primary epileptic syndrome. Management is usually difficult, and prognosis is that of the underlying disorder.
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