Identifying the structures involved in seizure generation using sequential analysis of ictal-fMRI data

Area of Science:

• Neuroimaging
• Epileptology
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Pharmaco-resistant focal epilepsy presents challenges in localizing seizure onset zones for effective treatment.
• Current methods like SISCOM and intracranial EEG have limitations in precision and invasiveness.
• Blood-oxygen-level-dependent (BOLD) signal changes during seizures offer a potential non-invasive marker.

Purpose of the Study:

• To evaluate the utility of sequential analysis of BOLD signal changes for preoperative identification of seizure onset.
• To compare fMRI findings with established methods like SISCOM and intracranial EEG.
• To assess the impact of resecting the identified seizure onset zone on patient outcomes.

Main Methods:

• Analysis of BOLD fMRI data from 5 patients with medically refractory focal epilepsy during partial seizures.
• Sequential analysis of seizure epochs using 10-second blocks to calculate continuous t-maps.
• Comparison of fMRI results with SISCOM and intracranial EEG in relevant cases.

Main Results:

• Sequential fMRI analysis consistently identified a localized area of signal increase at seizure initiation.
• This signal increase preceded clinical/EEG seizure onset by 6-52 seconds.
• Resection of the identified area led to seizure remission in most surgically treated patients.

Conclusions:

• Sequential ictal-fMRI analysis is a promising non-invasive tool for precise delineation of the ictal onset zone.
• This method provides insights into the brain's role in seizure generation and propagation.
• Accurate localization can improve surgical outcomes for epilepsy patients.