In 2001, ILAE Commission on Classification and Terminology proposed a diagnostic scheme of epilepsy that included a new concept of epileptic encephalopathy in which epileptic abnormalities contribute to a progressive disturbance in cerebral function.1 Also called catastrophic epilepsy, the earliest form of epileptic encephalopathies are Ohtahara syndrome (OS) and early myoclonic encephalopathy (EME).2,3,4 This chapter outlines OS and EME, referring to their treatment and prognoses.
The suppression–burst pattern (SB) is a unique EEG pattern in which bursts of high voltage paroxysmal activity and near-flat suppression appear alternately, and likely represents disconnection of the cortex from subcortical structures.2,3 Clinically, SB is also observed in (1) neonatal hypoxic–ischemic encephalopathy, in which it is usually called burst–suppression pattern, (2) deep anesthesia/sedation, and (3) neonatal epileptic encephalopathy such as OS and EME. SB in these latter disorders differs from the former two conditions; SB in the epileptic encephalopathy includes active epileptic discharges in bursts and has a shorter suppression phase than the former two transient nonepileptic conditions. To separate from other conditions with transient SB, Aicardi and Ohtahara3 considered that SB in the severe neonatal epilepsies must be stable or "invariant" for more than two weeks. As OS and EME share similar features besides SB such as very early onset, frequent and intractable seizures and severe prognoses, they are sometimes inclusively described such as early infantile epileptic syndromes with suppression–burst5 or severe neonatal epilepsies with suppression–burst pattern.3
Differential Diagnosis of Ohtahara and West Syndromes
The age at onset of the two syndromes is different: OS appears from the neonatal period to early infancy and West syndrome (WS) in middle infancy (Table 12–1).
TABLE 12–1.ELECTROCLINICAL FEATURES OF NEONATAL ENCEPHALOPATHIES |Favorite Table|Download (.pdf) TABLE 12–1. ELECTROCLINICAL FEATURES OF NEONATAL ENCEPHALOPATHIES
|Characteristics || ||Ohtahara Syndrome ||Early Myoclonic Encephalopathy ||West Syndrome |
|Age of onset || ||Early infancy (mainly neonatal) ||Early infancy (mainly neonatal) ||Middle infancy |
|Etiology || ||Polyetiology; mainly organic, malformative brain lesion (organic/static encephalopathy) ||Some metabolic disorders (metabolic encephalopathy) ||Polyetiology |
|Initial seizure type || ||Tonic spasms, partial seizures ||Myoclonia, partial seizures ||Tonic spasms |
| ||Nonepileptic myoclonia ||+ (erratic) ||+++ (erratic, fragmentary) ||– |
|Clinical seizure ||Tonic spasms ||Main seizure type (single/in series) ||Transiently in middle or late infancy (single/in series) ||Main seizure type (usually in series) |
| ||PS ||+ ||+++ (main seizure type) ||± |
| ||Sleep-wake cycle ||Diffuse ||Diffuse ||Awake |
|EEG ||Interictal ||SB ||SB (burst-suppression type in neonate) ||Hypsarrhythmia |
| ||Burst–burst interval ||Relatively regular ||Irregular (shorter burst and longer suppression in neonatal period) || |
|Sleep-wake cycle || ||Consistently, regardless of sleep-wake cycle ||Enhanced by sleep (after neonate) ||Periodic in sleep |
| ||Course of SB ||Transition to hypsarrhythmia or spike foci after middle infancy ||Persist even after ...|
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