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  • Updated 09.16.2020
  • Released 10.18.1993
  • Expires For CME 09.16.2023

Ohtahara syndrome

Introduction

Overview

Ohtahara syndrome is one of the earliest developing forms of epileptic encephalopathy. The syndrome is characterized by tonic spasms, focal seizures, a specific pattern of suppression bursts in EEG, and poor prognosis. In this article, the authors review the clinical, genetic, neurophysiologic, and etiologic data related to Ohtahara syndrome. The condition is classically thought to be mainly secondary to cerebral malformations. A variety of genetic mutations have increasingly been identified in subjects with Ohtahara syndrome. Metabolic disorders also have been reported as causes of the syndrome.

Key points

• Ohtahara syndrome is one of the earliest developing forms of epileptic encephalopathy.

• The main characteristics of the syndrome are tonic seizures and a suppression-burst pattern on EEG.

• Although the condition was classically attributed to structural brain damage, it has increasingly been associated with a variety of genetic mutations as well, most prominently involving the STXBP1, SCN2A, ARX, and KCNQ2 genes, though multiple other associations have been made.

• Prognosis is very poor.

Historical note and terminology

Early infantile epileptic encephalopathy with suppression bursts was first described by Ohtahara and colleagues in 1976 (35) and is considered one of the earliest forms of epileptic encephalopathy, the other being early myoclonic epilepsy of infancy. The 1989 revised classification by the International League Against Epilepsy placed the syndrome under "symptomatic generalized epilepsies and syndromes with nonspecific etiology" (06).

In 2001, the International League Against Epilepsy Task Force on Classification and Terminology proposed to include Ohtahara syndrome in the list of epileptic encephalopathies (09). These are conditions in which not only epileptic activity but also the epileptiform EEG abnormalities themselves are believed to contribute to the progressive disturbance in cerebral function. This group also includes early myoclonic encephalopathy, West syndrome, Dravet syndrome, Lennox-Gastaut syndrome, Landau-Kleffner syndrome, and electrical status epilepticus during sleep.

In 2010, the proposed organization presented by the Classification Commission of the International League Against Epilepsy included Ohtahara syndrome as an electroclinical syndrome, characterized by its clinical and EEG characteristics (03). The term “early infantile epileptic encephalopathy” is still used as well, referring either to Ohtahara syndrome specifically or to a spectrum of epileptic encephalopathy syndromes occurring during infancy, of which Ohtahara syndrome is one. This ambiguous terminology highlights the difficulty that can sometimes occur in distinguishing Ohtahara syndrome from other related syndromes such as early myoclonic encephalopathy.

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