Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 May;62(5):1105-1118.
doi: 10.1111/epi.16887. Epub 2021 Mar 29.

Localization of interictal discharge origin: A simultaneous intracranial electroencephalographic-functional magnetic resonance imaging study

Negar Tehrani  1   2 , William Wilson  1   2 , Daniel J Pittman  1   2 , Victoria Mosher  1   2 , Joseph S Peedicail  3 , Yahya Aghakhani  3 , Craig A Beers  1   2 , Ismael Gaxiola-Valdez  1   2 , Shaily Singh  3 , Bradley G Goodyear  1   2   4 , Paolo Federico  1   2   3   4 ; Calgary Comprehensive Epilepsy Program collaborators
Collaborators, Affiliations

Localization of interictal discharge origin: A simultaneous intracranial electroencephalographic-functional magnetic resonance imaging study

Negar Tehrani et al. Epilepsia. 2021 May.

Abstract

Objective: Scalp electroencephalographic (EEG)-functional magnetic resonance imaging (fMRI) studies suggest that the maximum blood oxygen level-dependent (BOLD) response to an interictal epileptiform discharge (IED) identifies the area of IED generation. However, the maximum BOLD response has also been reported in distant, seemingly irrelevant areas. Given the poor postoperative outcomes associated with extra-temporal lobe epilepsy, we hypothesized this finding is more common when analyzing extratemporal IEDs as compared to temporal IEDs. We further hypothesized that a subjective, holistic assessment of other significant BOLD clusters to identify the most clinically relevant cluster could be used to overcome this limitation and therefore better identify the likely origin of an IED. Specifically, we also considered the second maximum cluster and the cluster closest to the electrode contacts where the IED was observed.

Methods: Maps of significant IED-related BOLD activation were generated for 48 different IEDs recorded from 33 patients who underwent intracranial EEG-fMRI. The locations of the maximum, second maximum, and closest clusters were identified for each IED. An epileptologist, blinded to these cluster assignments, selected the most clinically relevant BOLD cluster, taking into account all available clinical information. The distances between these BOLD clusters and their corresponding IEDs were then measured.

Results: The most clinically relevant cluster was the maximum cluster for 56% (27/48) of IEDs, the second maximum cluster for 13% (6/48) of IEDs, and the closest cluster for 31% (15/48) of IEDs. The maximum clusters were closer to IED contacts for temporal than for extratemporal IEDs (p = .022), whereas the most clinically relevant clusters were not significantly different (p = .056).

Significance: The maximum BOLD response to IEDs may not always be the most indicative of IED origin. We propose that available clinical information should be used in conjunction with EEG-fMRI data to identify a BOLD cluster representative of the IED origin.

Keywords: blood oxygen level-dependent activity; focal epilepsy; functional MRI; interictal discharges; intracranial EEG; spike onset zone.

PubMed Disclaimer

References

REFERENCES

    1. Kowalczyk MA, Omidvarnia A, Abbott DF, Tailby C, Vaughan DN, Jackson GD. Clinical benefit of presurgical EEG-fMRI in difficult-to-localize focal epilepsy: a single-institution retrospective review. Epilepsia. 2020;61:49-60.
    1. Ives JR, Warach S, Schmitt F, Edelman RR, Schomer DL. Monitoring the patient’s EEG during echo planar MRI. Electroencephalogr Clin Neurophysiol. 1993;87:417-20.
    1. Moeller F, Tyvaert L, Nguyen DK, Levan P, Bouthillier A, Kobayashi E, et al. EEG-fMRI: adding to standard evaluations of patients with nonlesional frontal lobe epilepsy. Neurology. 2009;73:2023-30.
    1. Gotman J, Kobayashi E, Bagshaw AP, Bénar CG, Dubeau F. Combining EEG and fMRI: a multimodal tool for epilepsy research. J Magn Reson Imaging. 2006;23:906-20.
    1. Jäger V, Dümpelmann M, LeVan P, Ramantani G, Mader I, Schulze-Bonhage A, et al. Concordance of epileptic networks associated with epileptic spikes measured by high-density EEG and fast fMRI. PLoS One. 2015;10:1-20.

Publication types

LinkOut - more resources