<unk>  is rare and the earliest-appearing age-related epileptic encephalopathy, with seizure onset occurring within the first three months of life, and often in the first ten days. Many, but not all, cases of OS evolve into other seizure disorders, namely West<unk>  and Lennox-Gastaut<unk> . The primary outward manifestation of OS is seizures, usually presenting as tonic seizures (a generalized seizure involving a sudden stiffening of the limbs). Other seizure types that may occur include partial seizures, clusters of infantile spasms, and, rarely, myoclonic seizures. In addition to seizures, children with OS exhibit profound mental and physical disabilities. Clinically, OS is characterized by a "burst suppression" pattern on an EEG. This pattern involves high voltage spike wave discharge followed by little brain wave activity. It is named for the Japanese neurologist Shunsuke<unk>  (1930–2013), who identified it in 1976. Signs and symptoms MRIs of a normal individual (left) and a patient with microcephaly caused by genetic mutation (right) Both female and male infants born with OS may experience symptoms while asleep or awake. Many children die from OS within their first 2 years of life, while those who survive maintain physical and cognitive disabilities such as excessive fatigue, difficulty feeding, chest infections and slow developmental progress. Although birth history and head size of infants is typically normal, microcephaly may occur. Certain genetic variants manifest with additional signs such as dyskinetic movements and an atypical Rett-syndrome appearance. * Tonic seizures and spasms * Muscle stiffness * Dilated pupils * Diplegia * Hemiplegia * Tetraplegia * Ataxia * Dystonia
Ohtahara syndrome
Pallister–Killian syndrome
Cohen syndrome
Cohen-Gibson syndrome
Berdon syndrome
Scheie syndrome
Gleich's syndrome
Christianson syndrome