Authors :
Presenting Author: Sebastian Coleman, PhD, MSci – The Hospital for Sick Children
Hrishikesh Suresh, MD – The Hospital for Sick Children
Karim Mithani, MD, MEng – The Hospital for Sick Children
Simeon Wong, MHSc-BME – The Hospital for Sick Children
Puneet Jain, MD – The Hospital for Sick Children
Vann Chau, MD – The Hospital for Sick Children
Elizabeth Donner, MD, FRCPC – Hospital for Sick Children
Lauren Sham, MD – The Hospital for Sick Children
Shelly Weiss, MD – The Hospital for Sick Children
Stephanie Holowka, MRT(R) – The Hospital for Sick Children
Hiroshi Otsubo, MD, PhD – The Hospital for Sick Children
Ayako Ochi, MD, PhD – The Hospital for Sick Children
George Ibrahim, MD, PhD – The Hospital for Sick Children
Rationale:
Vagus nerve stimulation (VNS) is a common treatment for drug resistant epilepsy (DRE) in children. However, clinical outcomes to VNS are heterogeneous, with approximately half of children realising at least 50% reduction in seizure frequency (Englot et al., 2011), highlighting the need for preoperative markers of VNS response. Previous research has suggested that VNS reduces the rate of seizures by altering the connectivity of vagus nerve afferents, such as the thalamus and amygdala (Hachem et al., 2018). Differences in baseline functional connectivity could therefore explain the variability in VNS response.
Methods:
We analysed resting magnetoencephalography (MEG) data for 65 children with DRE, prior to VNS surgery. Data were projected into 52 cortical domains using a beamformer, and segments containing interictal epileptiform discharges were removed. Connectivity was calculated using amplitude envelopes within canonical frequency bands, and t-tests were performed to compare responders ( > 50% seizure reduction) and non-responders to VNS. Subsequent statistical matrices were thresholded at p < 0.05, subject to cluster permutation tests to correct for multiple comparisons. To support these results, we also analysed resting functional magnetic resonance imaging (fMRI) data for 50 children with DRE. The fMRI data were parcellated into the same atlas as the MEG data, and t-tests were performed to compare connectivity in responders and non-responders to VNS. Similarity between modalities was quantified using linear regression between t-statistical maps