14. EEG in Ohtahara syndrome and hereditary neurometabolic diseases

Abstract

Ohtahara syndrome is classified among early infantile progressive epileptic encephalopathies. EEG is characterized by a suppression burst pattern, which appears with onset of seizures and disappears within the first 6 months of life. It is characterized by periods of low voltage basic rhythm (below 5, 10 or 15 microvolts) of different duration (2–10 s) discontinued with paroxysmal high voltage theta or delta waves intermixed with sharp waves. This pattern can be persistent in all sleep stages in severe cases, or present only in sleep in milder ones. Underlying causes are disturbances of brain development as hemimegalencephaly, porencephaly, Aicardy syndrome, focal cortical dysplasias and hypoxic–ischemic encephalopathy. Early myoclonic encephalopathy usually starts in the first day of life and frequently before 10th day. The EEG also shows burst suppression pattern, but types of seizures are different from those in epileptic enhcephalopathy. Causal factors are inherited metabolic disorders (nonketotic hypeglycinemia, propionic aciduria, methylmalonic acidaemia, D-glyceric acidemia, sulphite and xanthine oxidase deficiency, Zellweger syndrome, molybdenum co-factor deficiency). EEG in B6 dependent epilepsy, maple sirup urine disease, pyridoxal phosphate oxidase deficiency could show burst suppression pattern, but also other discharges. In de Vivo disease, GLUT1 transporter deficiency, EEG may show very different findings.