High-Density EEG Source Imaging Guides SEEG Targeting and Reveals Subtle Cortical Dysplasia
Abstract number :
3.474
Submission category :
3. Neurophysiology / 3C. Other Clinical EEG
Year :
2025
Submission ID :
1465
Source :
www.aesnet.org
Presentation date :
12/8/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Nisha M. Hollingsworth, MD, MPH – The Johns Hopkins
Shashwat Pokharel, MBBS – The Johns Hopkins
Evan Bucklin, BS – The Johns Hopkins
Wesley Budd, DO – The Johns Hopkins
William Anderson, MD – The Johns Hopkins
Emily L. Johnson, MD, MPH – Johns Hopkins University
Doris Lin, MD – The Johns Hopkins
Mackenzie Cervenka, MD – Johns Hopkins University School of Medicine
Siddharth Gupta, MD – The Johns Hopkins
Rationale: Non-lesional intractable focal epilepsy poses major challenges for localization and surgical planning. EEG source imaging (ESI), especially using high density EEG (HD-EEG) arrays, during interictal and ictal activity offers improved non-invasive precision delineating the irritative and seizure onset zones. We report a case of a patient with longstanding intractable epilepsy where ESI directed an implanted SEEG electrode for confirmation of the ESI suggested epileptogenic focus and ultimately revealed an occult cortical dysplasia after review of the imaging.
Methods: The clinical, imaging and neurophysiologic data were collected as a part of a standard pre-surgical evaluation process. Interictal ESI was performed using a 128-channel HD-EEG array. Location of the HD-EEG electrodes were digitized using stereo camera tracking technology. An individualized boundary element method (BEM) head model was generated from the patient’s brain MRI. Additionally, ictal ESI was performed using seizures captured with standard density arrays in the epilepsy monitoring unit. Interictal and ictal activity were source localized using the equivalent current dipole (ECD) method. SEEG implantation was then guided by these findings, targeting the source-localized regions.
Results: The patient is a 28-year-old female with a 10-year history of seizures characterized by arousal from sleep then behavioral arrest with or without rightward head jerks and bilateral tonic-clonic seizures. Her seizures remained unresponsive to multiple antiseizure medications. Brain MRI and PET were normal. Multiple standard EEGs showed mixed generalized and focal features with a left-sided predominance. HD-EEG recordings captured twenty sharp waves that were included in the ESI analysis. Interictal ESI localized the averaged epileptiform activity to the posterior aspect of the mesial orbitofrontal cortex on the left. Ictal ESI also localized the seizure activity to the same region. SEEG targeting the source localized regions, confirmed the irritative zone and seizure onset zones to be the left mesial orbitofrontal cortex. The characteristic of profuse interictal discharges and an ictal onset pattern of fast poly-spike bursts followed by low voltage fast activity strongly suggested the presence of a focal cortical dysplasia. Retrospective MRI review, informed by the electrophysiological localization, revealed a likely subtle cortical dysplasia in the same region.
Conclusions: This case underscores the utility of HD-EEG and ESI in the presurgical evaluation of non-lesional intractable focal epilepsy, which remains underutilized in clinical practice. Moreover, it facilitated recognition of a subtle cortical malformation not appreciated on standard MRI review.
Funding: NA
Neurophysiology