Which findings on EEG are characteristic of specific neonatal seizure syndromes?

Updated: Oct 03, 2019
  • Author: Rosalia C Silvestri-Hobson, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Specific syndromes of neonatal seizures include the following:

  • Early myoclonic encephalopathy (EME) was first proposed by Aicardi in 1978 to describe neonates who had myoclonic jerks and a burst-suppression EEG pattern. [15] The main criteria include severe neurological abnormalities in otherwise healthy neonates with early fragmentary erratic myoclonia and a burst-suppression pattern. A microdysgenesic malformation or metabolic disorder may be discovered later.

  • Early infantile epileptic encephalopathy (EIEE) was proposed by Otahara in 1976 and includes infants who, within 3 months after birth, develop refractory tonic spasm, developmental delay, and a burst-suppression EEG pattern. [16] Most of these infants later develop a full-blown hypsarrhythmia in the context of West syndrome. Unlike EME, burst-suppression accompanies wakefulness as well as sleep. It is rarely familial but may be linked to cerebral malformations.

  • Benign idiopathic neonatal convulsions (BINC), also known as fifth day convulsions, can be seen in both symptomatic and cryptogenic infants and are associated with a favorable outcome. BINC are associated with a specific EEG parameter (even with the variability of clinical manifestations) of alternating sharp-theta bursts that are observed in the interictal period. Occasionally, seizures may be described as GTCS consisting in tonic extension of the arms and legs, cyanosis, and clonic jerks. [17] The EEG correlate to these events, however, despite being described as generalized, points to a unilateral frontocentral onset on either side as a sign of focal seizure with secondary generalization.

  • In 1966, Rett first described benign familial neonatal convulsions (BFNC), which are transmitted through autosomal dominant inheritance. [18] The gene is localized on the long arm of chromosome 20 with regular penetration but variable expression. The incidence (0.9-2.1%) as well as the prevalence of epilepsy at later stages of life is low. EEG patterns are nonspecific. Seizure phenotype is highly variable as well as EEG ictal expressions, occasionally demonstrating generalized suppression and seizure onset followed by symmetric rhythmic slow wave and diffuse spikes in infants exhibiting tonic-clonic seizures. [19] GTCS in infants younger than 2 years are extremely rare [20] probably due to the immaturity of the developing brain lacking substantial synchronization mechanisms in the absence of sufficient myelination and mature interhemispheric connections.

  • Benign myoclonic epilepsy in infants (BMEI) is a rare epileptic syndrome characterized only by generalized myoclonic seizures occurring in normal children during the first 2 years of life. A review by Auvin found a high incidence of a positive family history of febrile seizures or epilepsy suggesting the importance of the genetic factor in the pathogenesis of BMEI. [21] Reflex myoclonic seizures are frequently observed. VPA therapy is effective. BMEI may be followed by JME and, despite a favorable neuropsychological outcome, mental retardation can be observed.

  • Neonatal pyridoxine dependency is a rare autosomal recessive disorder, defined by the empirical resolution of all symptoms with pyridoxine administration. It is attributed to GAD deficiency in GABA synthesis, but no gene defect has been yet identified. The EEG pattern consists of repetitive runs of 1-4 Hz high-amplitude waves and spikes that are similar to the typical spike and wave discharges that are usually seen only in older children (see image below).
Pyridoxine-dependent syndrome - generalized spike- Pyridoxine-dependent syndrome - generalized spike-wave discharges.

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