EEG Source Localization of Temporal Encephaloceles
Abstract number :
2.074
Submission category :
3. Neurophysiology / 3G. Computational Analysis & Modeling of EEG
Year :
2022
Submission ID :
2204988
Source :
www.aesnet.org
Presentation date :
12/4/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
Benjamin Cox, MD – University of Alabama at Birmingham; Shruti Agashe, MD – Fellow, Neurology, Mayo Clinic Rochester; Kelsey Smith, MD – Fellow, Neurology, Mayo Clinic Rochester; Kiran Kanth, MD – Assistant Professor, Neurology, UC Davis; Jamie Van Gompel, MD, PhD – Profesor, Neurology and Otolaryngology, Mayo Clinic Rochester; Lily Wong-Kisiel, MD – Associate Professor, Neurology, Mayo Clinic Rochester; Benjamin Brinkmann, MD – Associate Professor, Neurology, Mayo Clinic Rochester
Rationale: Temporal encephaloceles have been increasingly recognized as a cause of drug-resistant temporal lobe epilepsy (DR-TLE), however the exact relationship between these two lesions and epileptogenesis is unclear optimal surgical treatment is currently unclear, however, EEG source localization (ESL) may play a role in informing approach to treatment.
Methods: We reviewed all patients at Mayo Clinic Rochester with drug resistant temporal lobe epilepsy and temporal encephaloceles between, who underwent limited resection of the encephalocele and had 1 year outcomes. ESL was performed using standard density scalp EEG of ictal and interictal activity. Temporal intermittent rhythmic delta activity (TIRDA) was included and was analyzed separately from interictal activity. Dipole and sLORETA solutions were performed and the distance from result to the encephalocele center was measured. Rhythmic activity (both TIRDA and ictal onset) was analyzed in 2 separate ways: (1) averaging rhythmic waveforms at peak and (2) performing epoch analysis using ICA to subtract artifact. Concordance of ESL with encephalocele and surgical resection was compared with 1-year surgical outcomes.
Results: Eighteen patients met criteria. Mean distance (mm) from ESL dipole results to encephalocele center was 21.5 interictal spikes, 34.1 for TIRDA averaged, 26.0 for TIRDA epoch, 26.3 fo ictal averaged, and 24.2 fir ictal epoch. Distances for sLORETA results were 19.2, 31.3, 27.1, 23.1, and 24.4, respectively, showing a non-significant trend towards closer distances with sLORETA ictal averaged results. Comparison of methods for rhythmic analysis showed a trend towards closer distances with TIRDA epoch analysis (26.0mm vs 34.1mm for dipole, p=0.08; 27.1mm vs 31.4mm for sLORETA, p=0.14). Ictal ESL showed a trend towards closer distances with dipole analysis using averaged waveforms, however, the epoch analysis had no difference. Ten patients (55.6%) were seizure free at 1 year. Dipole or sLORETA localization to resection cavity did not show a difference in surgical outcomes. There was a trend towards increased distance from dipole to encephalocele with ictal and interictal analyses in patients with excellent surgical outcomes. There was a significant increased distance in sLORETA to encephalocele distance in patients with excellent outcomes in ictal epoch analyses (mean 29.6mm vs 18.6mm, p=0.0134).
Conclusions: Our cohort demonstrates ESL of scalp EEG localizes near encephaloceles, however, typically not in the encephalocele itself; this may be due to scalp EEG sampling propagated activity or alternatively, may suggest that the seizure onset zone extends beyond the herniated cortex. We did not see a consistent difference in methodology comparing averaged and epoch analysis of rhythmic activity, suggesting either method may have potential clinical utility. Surprisingly, we observed a trend of increased ESL to encephalocele distances in patients who were seizure free at 1 year after undergoing a focal resection. Larger cohort studies including intracranial EEG are needed to explore the trends observed in our cohort.
Funding: None
Neurophysiology