Initial delta and delayed theta/alpha pattern in the temporal region on ictal EEG suggests purely hippocampal epileptogenicity in patients with mesial temporal lobe epilepsy

Izumi Itabashi, Kazutaka Jin, Shiho Sato, Hiroyoshi Suzuki, Masaki Iwasaki, Yu Kitazawa, Yosuke Kakisaka, Nobukazu Nakasato

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: To determine whether the ictal scalp EEG findings suggest purely hippocampal epileptogenicity in patients with mesial temporal lobe epilepsy (mTLE) associated with hippocampal sclerosis (HS). Methods: Twenty-three patients with mTLE with pathologically confirmed HS were divided into 12 with epileptogenicity only in the hippocampus (HS only group) and 11 with epileptogenicity in both the hippocampus and temporal neocortex or other locations (HS plus group), based on the combination of surgical procedures, postoperative outcome, and pathological findings. Sixteen underwent selective amygdalohippocampectomy (SelAH) and 7 received anterior temporal lobectomy. Ictal scalp EEG findings of 79 focal impaired awareness seizures were compared between the HS only and HS plus groups. We focused on the 1–4 Hz rhythmic delta activity at ictal onset followed by 5–9 Hz rhythmic theta/alpha activity 10–30 s after the onset in the temporal region. Results: The initial delta and delayed theta/alpha (ID-DT) pattern was observed in 8 of 12 patients in the HS only group, but in none of 11 patients in the HS plus group (p < 0.01). Conclusions: ID-DT pattern on ictal EEG suggests purely hippocampal epileptogenicity in mTLE with HS. Significance: Patients with the ID-DT pattern are likely to become seizure-free after SelAH.

Original languageEnglish
Pages (from-to)737-743
Number of pages7
JournalClinical Neurophysiology
Volume132
Issue number3
DOIs
Publication statusPublished - 2021 Mar
Externally publishedYes

Keywords

  • Anterior temporal lobectomy
  • Hippocampal sclerosis
  • Ictal EEG
  • Mesial temporal lobe epilepsy
  • Selective amygdalohippocampectomy

ASJC Scopus subject areas

  • Sensory Systems
  • Neurology
  • Clinical Neurology
  • Physiology (medical)

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