Ictal and interictal electric source imaging in pre-surgical evaluation: a prospective study

Area of Science:

• Neuroscience
• Medical Imaging
• Epileptology

Background:

• Accurate epileptic focus localization is critical for drug-resistant epilepsy surgical treatment.
• Electric Source Imaging (ESI) is increasingly used in pre-surgical evaluation.
• Limited prospective studies compare interictal (II) and ictal (IC) ESI feasibility and accuracy.

Purpose of the Study:

• To prospectively compare the feasibility and accuracy of interictal (II) and ictal (IC) Electric Source Imaging (ESI).
• To evaluate ESI methods (ECD and DSM) against conventional neuroimaging and intracranial recordings.
• To assess ESI's correlation with surgical outcomes in drug-resistant epilepsy patients.

Main Methods:

• Prospective analysis of long-term video-electroencephalography (LTM) recordings in 87 epilepsy patients.
• Performed ESI using equivalent current dipole (ECD) and distributed source model (DSM) on II and IC signals.
• Compared ESI results with intracranial recordings, MRI, PET, SPECT, and 1-year post-operative seizure freedom.

Main Results:

• ESI localized focal abnormalities in 94% of patients, outperforming MRI (70%), PET (66%), and SPECT (64%).
• Agreement between ESI methods and intracranial recordings was moderate to substantial (k=0.56-0.79).
• Localization accuracy for II-ESI was 51-57%, and for IC-ESI was 51-62%, with no significant differences between ESI methods or compared to MRI.

Conclusions:

• Interictal (II) and ictal (IC) ESI of LTM data demonstrate high feasibility.
• ESI's localization accuracy is comparable to conventional neuroimaging methods (MRI, PET, SPECT).
• ESI is a valuable tool for pre-surgical evaluation in drug-resistant epilepsy.