Electroencephalographic change of non-affected side of hemimegalencephaly and developmental progress after hemispherotomy

Koji Takahashi, Eiji Nakagawa, Eri Takeshita, Yuko Motohashi, Akihiko Ishiyama, Takashi Saito, Hirofumi Komaki, Kenji Sugai, Yosuke Kita, Akio Takahashi, Taisuke Otsuki, Masayuki Sasaki

Research output: Contribution to journalArticlepeer-review


Hemimegalencephaly is characterized by severe psychomotor impairment and intractable epilepsy, which is often requires a hemispherotomy. After hemispherotomy, epileptic discharges may sometimes occur in the non-affected hemisphere even when clinical seizures do not recur for a long time. We evaluated six cases of hemimegalencephaly after hemispherotomy with a seizure-free period lasting at least 36 months, which we could track using video-electroencephalography. Developmental age (DA) and developmental quotient (DQ) were evaluated using the developmental check-list (Kinder Infant Developmental Scale). We found the DQ declined and the total DA increased in all cases. To study the correlation between DA and epileptic discharges in the non-affected hemisphere, we measured the paroxysmal-index (PI) the number of one-second bins containing one or more epileptic discharges in the non-affected hemisphere, divided by the total number of seconds. The PI and DA data were collected at the same time during every regularly-scheduled evaluation. We calculated the rate of change of PI and DA. Interestingly, expressive language development and PI were negatively correlated when the PI increased at a rate above average. The receptive language DA and PI was not correlated. This finding suggests the expressive language development delay may worsen when epileptic discharges of non-affected side increase.

Original languageEnglish
Pages (from-to)619-627
Number of pages9
JournalJournal of the Japan Epilepsy Society
Issue number3
Publication statusPublished - 2017
Externally publishedYes


  • Electroen-cephalography
  • Hemimegalencephaly
  • Hemispherectomy
  • Non-affected side
  • Verbal development

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology


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