Page 156 - MEGIN Book Of Abstracts - 2023

NatMEG, Department of Clinical Neuroscience, Karolinska Keywords: Epilepsy, Interictal epileptiform discharges,
Institutet, Stockholm, Sweden; Clinical Neurophysiology, Low-frequency oscillations, Magnetoencephalography,
Karolinska University Hospital, Stockholm, Sweden. Electronic Synchronization
address: [email protected]; Clinical Neurophysiology, Clinical
Neuroscience, Karolinska Institutet, Stockholm, Sweden; De- Clinical neurophysiology: official journal of the
partment of Neurophysiology, Great Ormand Street Hospital International Federation of Clinical Neurophysiology
for Children, London, UK; Department of Clinical Neurophysi- (2022), Vol. 136 (35217349) (2 citations)
ology, Aarhus University Hospital, Denmark and Danish
Epilepsy Centre, Dianalund, Denmark
Virtual intracranial EEG signals reconstructed from
OBJECTIVE Interictal epileptiform discharges (IEDs) MEG with potential for epilepsy surgery (2022)
constitute a diagnostic signature of epilepsy. These
events reflect epileptogenic hypersynchronization. Pre- Cao, Miao; Galvis, Daniel; Vogrin, Simon J; Woods,
vious studies indicated that IEDs arise from slow neuro- William P; Vogrin, Sara; Wang, Fan; Woldman, Wessel;
nal activation accompanied by metabolic and hemody- Terry, John R; Peterson, Andre; Plummer, Chris; Cook,
namic changes. These might induce cortical inhibition Mark J
followed hypersynchronization at IED onset. As cortical
inhibition is mediated by low-frequency oscillations, we Centre for Clinical Neurosciences and Neurological Research,
aimed to analyze the role of low-frequency oscillations St Vincent's Hospital Melbourne, Melbourne, Australia;
prior the IED using magnetencephalography (MEG). Institute of Metabolism and Systems Research, University of
Birmingham, Birmingham, UK; Faculty of Health, Art and
METHODS Low-frequency (1-8 Hz) oscillations pre- Design, Swinburne University of Technology, Melbourne,
IED ([-1000 milliseconds (ms), IED onset]) were ana- Australia; Department of Medicine Western Health, The
lyzed using MEG in 14 focal epilepsy patients (median University of Melbourne, Melbourne, Australia; University of
age = 23 years, range = 7-46 age). Occurrence of local Chinese Academy of Sciences, Beijing, China; Department
pre-IED oscillations was analyzed using Beamformer of Biomedical Engineering, The University of Melbourne,
Dynamical Imaging of Coherent Sources (DICS) and Melbourne, Australia; Faculty of Health, Art and Design,
event-related desynchronization/synchronization (ERD- Swinburne University of Technology, Melbourne, Australia.
ERS) maps constructed using cluster-based permuta- [email protected]
tion tests. The development of pre-IED oscillations was
characterized using Hilbert transformation. ABSTRACT Modelling the interactions that arise from
neural dynamics in seizure genesis is challenging but
RESULTS All patients exhibited statistically signifi- important in the effort to improve the success of epi-
cant increase in delta (1-4 Hz) and/or theta (4-8 Hz) lepsy surgery. Dynamical network models developed
oscillations pre-IED compared to baseline [-2000 ms, from physiological evidence offer insights into rapidly
-1000 ms]. Furthermore, all patients exhibited low- evolving brain networks in the epileptic seizure. A
frequency power increase up to IED onset. limitation of previous studies in this field is the de-
pendence on invasive cortical recordings with con-
CONCLUSIONS We demonstrated consistently occur- strained spatial sampling of brain regions that might
ring, low-frequency oscillations prior to IED onset. be involved in seizure dynamics. Here, we propose
virtual intracranial electroencephalography (ViEEG),
SIGNIFICANCE As low-frequency activity mediates which combines non-invasive ictal magnetoencephalo-
cortical inhibition, our study demonstrates that a focal graphic imaging (MEG), dynamical network models and
inhibition precedes hypersynchronization at IED onset. a virtual resection technique. In this proof-of-concept
study, we show that ViEEG signals reconstructed from
MEG alone preserve critical temporospatial character-

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