Trainee Project
Electrical Source Imaging of interictal and ictal discharges in drug-refractory frontal lobe epilepsies, during simultaneous SEEG-scalp EEG recordings structurelles frontales enregistrées simultanément en EEG de surface et en SEEG.
2021/11/01 - 2022/10/31
Structural drug refractory focal epilepsies are frequent, representing roughly 25% of all epilepsies. These patients
are referred to tertiary centers to assess whether they could be remediable by resective surgery. This fonctionnal
and curative neurosurgery relies on the identification and delineation of the cortical area responsible for the
initiation of seizures, called epileptogenic zone (EZ). Although this EZ corresponds in most cases to structural
cerebral abnormalities, the current structural or even functional imaging technics (MRI, FDG-PET) fail to localize
and delineate precisely the EZ (Maillard et al., 2017). There is indeed a frequent discordance (partial or total)
between the EZ and the structural abnormality when the latter is visible and in 40% of cases there is no structural
abnormality visible on MRI in cases of focal cortical dysplasia (the most frequent cause of drug refractory
epilepsies in the frontal lobe). Frontal lobe epilepsies are one of the most invalidating form of focal structural
epilepsies because the seizures are violent, consist in hyperkinetic manifestations, with possible falls, occur at
night and are associated with social, cognitive and motor behavior disorders.(Beleza, J Clin Neurosci, 2011)
Electrical source imaging is a low-cost clinical neurophysiological technique that combines the high temporal
resolution of EEG with the high spatial resolution of MRI. It allows modelizing the cortical sources of detected
surface EEG ictal events and contributes to localize the presumed EZ and therfore to guide the implantation of
intra-cerebral electrodes for intra-cerebral recordings (SEEG) that is the gold-standard to delineate the EZ.
(National Research Council (US) and Institute of Medicine, 1996) (Michel Christoph, Frontiers in Neurology, 2019)
ESI is more specific and sensitive than MRI and FDG-PET to determine the presumed EZ. (Malpass, Nat Rev
Neurol, 2011). One of the issue however is that ESI requires first to identify epileptic discharges visible on the
scalp. Based on simultaneous intra-cranial-surface EEG recordings, we showed that only 16% of intra-cerebral
epileptic sources identified by intra-cranial EEG are actually visible en scalp EEG. A second issue is that in frontal
lobe epilepsy, the concordance between ESI derived from interictal surface EEG discharge with the EZ remains
insufficient. Our hypothesis is that this lack of concordance might be related to the fact that the more focal intra-
cerebral epileptic sources remain undetectable on scalp EEG by visual analysis alone ((Koessler, Brain Topography,
One way to test this hypothesis would be to extract epileptic events from the background activity on the surface
EEG based on simultaneous scalp EEG and intracerebral recordings (Ramantani, Epilepsia, 2014) and to apply ESI
techniques on these events and compare their localizing value to the localizing value of ESI derived from non
simultaneous HR-EEG.
In this monocentric retrospective observational study (performed in a tertiary epilepsy center, national center of
reference for rare epilepsies), all clinical and neurophysiological data are already available, as well as the
softwares and the research and clinical expertise to analyse and interpret the findings.
This project will be performed under the supervision of Pr Maillard (head of the epilepsy center of Nancy) and of
Dr KOESSLER (chargés de recherche CNRS, expert in EEG and ESI)
SEEG, HR-EEG, epilepsy, frontal lobe, electrical source imaging
Biology, Signals and Systems in Cancer and Neuroscience
Rikir et al., 2020, Ramantani et al., 2014, Koessler et al., 2014, 2015, Abdallah et al., 2017    + CRAN - Publications