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

•Twenty-three patients with mesial temporal lobe epilepsy with pathologically confirmed hippocampal sclerosis were reviewed.•Ictal EEG findings of the initial delta and delayed theta/alpha pattern suggest purely hippocampal epileptogenicity.•Patients with this pattern are likely to become seizure-fr...

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Published in:Clinical neurophysiology 2021-03, Vol.132 (3), p.737-743
Main Authors: Itabashi, Izumi, Jin, Kazutaka, Sato, Shiho, Suzuki, Hiroyoshi, Iwasaki, Masaki, Kitazawa, Yu, Kakisaka, Yosuke, Nakasato, Nobukazu
Format: Article
Language:English
Subjects:
Anterior temporal lobectomy
Hippocampal sclerosis
Ictal EEG
Mesial temporal lobe epilepsy
Selective amygdalohippocampectomy
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Summary:•Twenty-three patients with mesial temporal lobe epilepsy with pathologically confirmed hippocampal sclerosis were reviewed.•Ictal EEG findings of the initial delta and delayed theta/alpha pattern suggest purely hippocampal epileptogenicity.•Patients with this pattern are likely to become seizure-free after selective amygdalohippocampectomy. 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). 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. 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 
ISSN:1388-2457
1872-8952
DOI:10.1016/j.clinph.2020.11.041