Authors :
Presenting Author: Giovanni Pellegrino, MD, PhD – Western University
Eliane Kobayashi, MD, PhD – MNI – McGill University; Victoria Ros, MD – McGill University
Rationale:
Temporal lobe epilepsy (TLE) is characterized by an unbalance of excitation/inhibition (E/I) and progressive cortical thinning. Measuring E/I in vivo, especially at non-primary cortical regions, remains challenging. New E/I indexes from resting state magnetoencephalography (MEG) are emerging, but their potential applications in epilepsy remain unknown. We applied new measures of E/I balance to address their relationship with cortical thickness in TLE patients.
Methods:
Thirty-two TLE patients (17L) underwent MEG for E/I estimation and high-resolution 3T MRI for head modeling and cortical thickness assessment. Six-minute wakefulness resting state activity was reconstructed at cortical level. The exponent and offset of the aperiodic component of the power-spectrum, as well as cortical thickness, were modeled vertex-wise. A sample of 127 MEG recordings from healthy subjects was used as reference.
Results:
Compared to healthy subjects, TLE patients showed higher exponent and offset in the anterior temporal regions. The exponent increase was lateralized and concordant with the focus side (82% for left and 73% for right). There was a significant positive correlation between cortical thickness and exponent in the precentral regions.
Conclusions:
New measures from resting state MEG appear to demonstrate sensitivity to E/I unbalance in TLE and are linked to well-known structural changes occurring in in these patients. The increase of both offset and exponent suggests that E/I change are most likely driven by increased neuronal population spiking. The topographical specificity of the exponent may be considered as complementary measure to assess focus laterality in TLE.
Funding: Fred Andermann fellowship in epilepsy and EEG