MEG Slow Wave Activity Associated with Brain Tumors in Patients with and Without Epilepsy
Abstract number :
2.042
Submission category :
3. Neurophysiology / 3D. MEG
Year :
2023
Submission ID :
424
Source :
www.aesnet.org
Presentation date :
12/3/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: Daniel Zhou, MD – University of Pennsylvania
Olga Taraschenko, MD, PhD – Department of Neurological Sciences – University of Nebraska Medical Center; Noam Peled, PhD – MGH/HST Martinos Center for Biomedical Imaging – Harvard Medical School; Oleg Korzyukov, PhD – Department of Neurological Sciences – University of Nebraska Medical Center; Valentina Gumenyuk, PhD – Department of Neurological Sciences – University of Nebraska Medical Center
Rationale:
Epilepsy is prevalent in nearly half of patients with primary brain tumors. Recent evidence suggests that brain tumors can generate abnormal electrical activity in peritumoral tissue and affect local brain networks. Magnetoencephalography (MEG), a noninvasive imaging tool used for the functional mapping of eloquent cortex and localization of epileptogenic brain regions, has been used for cortical mapping prior to resective surgery. However, the evaluation of spontaneous interictal activity is often omitted. We aimed to characterize the interictal activity, including epileptiform discharges and slow activity, of patients who received presurgical MEG and compare the results between patients with and without brain tumor-related epilepsy (BTRE).
Methods:
We performed a retrospective analysis of the spontaneous interictal recordings in MEG during awake and sleep states in patients with primary gliomas who were recorded at the University of Nebraska Medical Center from July 2021 to March 2023. Focal slow wave activity (delta-theta band) was identified and processed for source localization using the equivalent current dipole method with Neuromag and Curry software. Dipoles were accepted when the goodness of fit was ≥80% and superimposed onto the individual patient’s brain MRI. A cluster was formed when ≥5 dipoles were localized closely together. Pre- and post-operative brain MRIs were used to determine tumor and resection sizes and locations, and the dipoles were then localized against the tumor resection sites.
Results:
Six patients with median age 26.5 years (range 25-75), four female, diagnosed with low or high grade oligodendroglioma or astrocytoma, were included (Table 1). Four had BTRE. Tumors in patients with BTRE were larger than in those without BTRE. On review of MEG waveform data, no spikes were detected in the tumor or peritumoral regions in all patients. Five patients had focal slow activity in and near the region of the tumor with higher amplitudes in sleep compared to the awake state. The number of MEG dipoles representing source localization of slow wave activity was higher in patients with BTRE (mean 19.25 dipoles) compared to those without BTRE (mean 3 dipoles). The dipoles appeared in clusters in the BTRE group with most dipoles localized within 1 cm of the tumor margin. In the example of patient #4 with BTRE, the cluster of dipoles appeared near the left parietal tumor with spread to the adjacent temporal lobe (Fig. 1A). Focal slow activity was maximal adjacent to the tumor and extended to the temporal lobe, as shown on 3-D reconstructed brain (Fig. 1C-D). Spectral analysis showed greater peritumoral slow activity detected in gradiometers than in scalp EEG (Fig. 1D-E).
Conclusions:
Increased focal slow activity in the tumor site and surrounding areas may be related to pathologic and structural contributions. The epileptogenic potential of these changes remains to be determined. The inclusion of spontaneous interictal activity with sleep in MEG evaluation of brain tumor patients provides insight into the tumor’s effects on regional brain activity.
Funding:
Neurophysiology