Presurgical EEG-fMRI Mapping of Epileptic Discharges aids Stereo-EEG Planning and RF ablation
Poster No:
310
Submission Type:
Abstract Submission
Authors:
David Vaughan1,2,3, John Archer2,3, David Abbott1,2, Marty Bryant1, Kristian Bulluss2,3,4, Chris Tailby1,2,3, Graeme Jackson1,2,3
Institutions:
1The Florey Institute of Neuroscience and Mental Health, Melbourne, Australia, 2University of Melbourne, Victoria, Australia, 3Austin Health, Melbourne, Australia, 4St Vincent's Hospital Melbourne, Victoria, Australia
First Author:
David Vaughan
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
Co-Author(s):
David Abbott, PhD
The Florey Institute of Neuroscience and Mental Health|University of Melbourne
Melbourne, Australia|Victoria, Australia
The Florey Institute of Neuroscience and Mental Health|University of Melbourne
Melbourne, Australia|Victoria, Australia
Kristian Bulluss
University of Melbourne|Austin Health|St Vincent's Hospital Melbourne
Victoria, Australia|Melbourne, Australia|Victoria, Australia
University of Melbourne|Austin Health|St Vincent's Hospital Melbourne
Victoria, Australia|Melbourne, Australia|Victoria, Australia
Chris Tailby
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
Graeme Jackson
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
The Florey Institute of Neuroscience and Mental Health|University of Melbourne|Austin Health
Melbourne, Australia|Victoria, Australia|Melbourne, Australia
Introduction:
Stereo-electroencephalography (sEEG) has emerged as a pivotal diagnostic tool for identifying the location of seizure onset in people with drug-resistant focal epilepsy. It involves stereotactic implantation of electrodes into the brain, to record epileptic electrical activity and determine which regions are involved in discharge generation (Isnard, 2018). The goal is to enable safe surgical removal of the critical brain region for effective epilepsy treatment. Additionally, radio-frequency ablation (RFA), a precise treatment to deliver small brain lesions delivered via the implanted sEEG electrodes, can be highly beneficial when targeted accurately (Kerezoudis, 2022).
However, utility of sEEG, and the effectiveness of RFA, both critically depend on the pre-planned location of the intracranial electrodes. Traditionally electrode positions are planned from brain anatomy, seizure symptoms and scalp EEG findings – forms of data which each have limited spatial resolution. To address this issue, we investigated whether presurgical simultaneous EEG and functional MRI (EEG-fMRI), a technique to non-invasively map epileptic discharges, has complementary value for electrode targeting and maximising the benefit of sEEG.
However, utility of sEEG, and the effectiveness of RFA, both critically depend on the pre-planned location of the intracranial electrodes. Traditionally electrode positions are planned from brain anatomy, seizure symptoms and scalp EEG findings – forms of data which each have limited spatial resolution. To address this issue, we investigated whether presurgical simultaneous EEG and functional MRI (EEG-fMRI), a technique to non-invasively map epileptic discharges, has complementary value for electrode targeting and maximising the benefit of sEEG.
Methods:
We performed EEG-fMRI in people with refractory focal epilepsy during pre-surgical workup for sEEG at Austin Health (2019-2024). Up to 1 hour of continuous in-scanner recording was obtained with the participant resting quietly with eyes closed (Kowalczyk, 2020). Scalp EEG was recorded with 64-channel (BrainVision) or 256-channel (Magstim-EGI) caps. Functional MRI was recorded on a 3T Siemens Prisma or Vida scanner, using multi-band multi-echo echoplanar imaging (cmrr.umn.edu/multiband; 3mm3 voxels, TR 900ms, TE 13.4 / 33.0 / 52.5ms, MB 4, GRAPPA 2, partial Fourier 7/8). Epileptic discharges were identified on the EEG and their timings used to perform fMRI general linear model analysis in SPM12, and event-related Independent Components Analysis (Masterton, 2013).
Curated EEG-fMRI results were provided to the treating team and relevant BOLD activation maps co-registered into the neurosurgical planning workflow. Following the sEEG procedure, medical records were reviewed to determine modifications in the sEEG plan due to the EEG-fMRI data, the sEEG-determined epileptogenic zone, whether RFA was delivered, and the final clinical outcome.
Curated EEG-fMRI results were provided to the treating team and relevant BOLD activation maps co-registered into the neurosurgical planning workflow. Following the sEEG procedure, medical records were reviewed to determine modifications in the sEEG plan due to the EEG-fMRI data, the sEEG-determined epileptogenic zone, whether RFA was delivered, and the final clinical outcome.
Results:
EEG-fMRI was performed prior to sEEG planning in 11 adults with refractory focal epilepsy (6 male, ages 25-53 years). Structural MRI was normal (55%) or showed extensive structural pathology (45%) such as nodular heterotopia or polymicrogyria. Median seizure frequency was 4.6/week (range 1-14/week) despite mean 3.5 (range 2-4) anti-seizure medications.
EEG-fMRI generated statistically significant interictal activation maps and provided additional information to localize the epileptic focus in 9 of 11 (82%) of cases. The sEEG plan was revised based on the EEG-fMRI result in 8 cases, with a mean of 2.9 electrodes being added/modified out of the overall mean 13.0 electrodes per participant. These modified electrodes identified or provided additional coverage of the final sEEG-determined epileptogenic zone in 88% of cases (7 out of 8).
RFA was performed at the epileptogenic zone in 10 patients. Electrodes positioned because of the EEG-fMRI result were utilized to deliver ablation in 50% of cases. Seizure outcomes were good when RFA was delivered using EEG-fMRI-guided electrodes; 80% of such cases (4 of 5) had transient early seizure freedom at 1 month, with 40% having sustained good outcomes.
EEG-fMRI generated statistically significant interictal activation maps and provided additional information to localize the epileptic focus in 9 of 11 (82%) of cases. The sEEG plan was revised based on the EEG-fMRI result in 8 cases, with a mean of 2.9 electrodes being added/modified out of the overall mean 13.0 electrodes per participant. These modified electrodes identified or provided additional coverage of the final sEEG-determined epileptogenic zone in 88% of cases (7 out of 8).
RFA was performed at the epileptogenic zone in 10 patients. Electrodes positioned because of the EEG-fMRI result were utilized to deliver ablation in 50% of cases. Seizure outcomes were good when RFA was delivered using EEG-fMRI-guided electrodes; 80% of such cases (4 of 5) had transient early seizure freedom at 1 month, with 40% having sustained good outcomes.
Conclusions:
EEG-fMRI can provide non-invasive pre-surgical data to more effectively target sEEG electrodes. In our cohort, this approach increased the likelihood of the epileptogenic zone being sampled. Enhanced placement of intracranial electrodes facilitates delivery of RF ablation as both a diagnostic and therapeutic procedure, especially in difficult-to-localize epilepsy (Figure 1).
Disorders of the Nervous System:
Neurodevelopmental/ Early Life (eg. ADHD, autism) 1
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 2
Keywords:
ADULTS
Electroencephaolography (EEG)
Epilepsy
FUNCTIONAL MRI
Treatment
Other - Intracranial
1|2Indicates the priority used for review
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Provide references using APA citation style.
Kerezoudis et al. (2022). Systematic review and patient-level meta-analysis of radiofrequency ablation for medically refractory epilepsy: Implications for clinical practice and research. Seizure: European Journal of Epilepsy, 102, 113–119.
Kowalczyk et al. (2020). Clinical benefit of presurgical EEG-fMRI in difficult-to-localize focal epilepsy: A single-institution retrospective review. Epilepsia, 61(1), 49–60.
Masterton et al. (2013). Mapping brain activity using event-related independent components analysis: Specific advantages for EEG-fMRI. NeuroImage, 70, 164–174.