Evaluation of interhemispheric time difference by magnetoencephalography before and after total callosotomy - Two case reports

Kamran Ali Salayev, Nobukazu Nakasato, Mamiko Ishitobi, Hiroshi Shamoto, Akitake Kanno, Teiji Tominaga, Kazuie Iinuma

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Interhemispheric time difference (ITD) measured by electroencephalography (EEG) and magnetoencephalography (MEG) was compared to seizure outcome after callosotomy. Two patients with frequent drop attacks underwent simultaneous EEG and MEG before and after total callosotomy. ITDs in 30 bilateral synchronized (BS) discharges were calculated independently by EEG and MEG. As minimum transcallosal conduction time was suggested to be approximately 20 msec, BS discharges were classified into five categories according to ITD and side: left- or right-leading long (300 to 80 msec), left- or right-leading moderate (80 to 20 msec), and negligible (< 20 msec). In Case 1 before callosotomy, EEG detected 77% negligible and 23% right-leading moderate BS discharges, whereas MEG detected 30% and 63%, respectively. After callosotomy, drop attacks reduced remarkably and EEG and MEG detected no BS discharges. In Case 2 before callosotomy, EEG detected 77% negligible and 23% moderate BS discharges, whereas MEG detected 80% and 20%, respectively. After callosotomy, drop attacks recurred 2 months later and EEG and MEG detected left- and right-leading long BS discharges (63% by EEG and 56% by MEG). MEG detected a large number of BS discharges with moderate ITD before surgery in Case 1, suggesting that the transcallosal pathway was the main pathway for the synchronization, whereas the negligible ITD in Case 2 excludes transcallosal propagation. BS discharges with longer ITD after surgery in Case 2 suggest a persistent poly-synaptic non-transcallosal pathway. MEG with higher spatial resolution than EEG may provide surgical indications for callosotomy.

Original languageEnglish
Pages (from-to)136-142
Number of pages7
JournalNeurologia medico-chirurgica
Volume46
Issue number3
DOIs
Publication statusPublished - 2006 Mar

Keywords

  • Callosotomy
  • Electroencephalography
  • Magnetoencephalography
  • Secondary bilateral synchrony

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

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