Two cases of early-onset myoclonic seizures with continuous parietal delta activity caused by EEF1A2 mutations

Takehiko Inui, Satoru Kobayashi, Yuka Ashikari, Ryo Sato, Wakaba Endo, Mitsugu Uematsu, Hiroshi Oba, Hirotomo Saitsu, Naomichi Matsumoto, Shigeo Kure, Kazuhiro Haginoya

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


Background Mutations in the elongation factor 1 alpha 2 (EEF1A2) gene have recently been shown to cause severe intellectual disability with early-onset epilepsy. The specific manifestations of mutations in this gene remain unknown. Case report We report two cases of severe intellectual disability accompanied by early-onset epilepsy with continuous delta activity evident on electroencephalography. Both cases presented with developmental delay and repetitive myoclonic seizures in early infancy. Both cases showed continuous high-voltage delta activity over both parietal areas when awake, as revealed by interictal electroencephalograms. After the emergence of continuous delta activity, development stagnated. One case showed some development after relief of the seizures and epileptic activity, but drug resistant seizures recurred, and the development again became stagnant. In both cases, a de novo recurrent heterozygous mutation in EEF1A2 [c.364G > A (p.E122K)] was identified by whole-exome sequencing. Conclusion This report provides clinical data on epileptic encephalopathy in patients with EEF1A2 mutation. Continuous high-voltage delta activity seen over both parietal areas may be a unique manifestation of EEF1A2 mutation. Epileptic activity may aggravate the effect of the mutation on brain development.

Original languageEnglish
Pages (from-to)520-524
Number of pages5
JournalBrain and Development
Issue number5
Publication statusPublished - 2016 May 1


  • EEF1A2
  • Epilepsy
  • Genetics
  • High voltage delta activity
  • Intellectual disability
  • Myoclonic seizure
  • Pediatrics

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Developmental Neuroscience
  • Clinical Neurology


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