Javier Urriola of the Reutens Group,
Neuroimaging biomarkers in epilepsy, 
Centre for Advanced Imaging, presents: 

High-frequency oscillations for the localisation of the seizure onset zone

The surgical treatment of epilepsy is vastly underutilised and is often delayed despite its proven high efficacy in controlling drug-resistant focal epilepsy. A significant number of surgical candidates are ruled out from the surgical pathway due to discordant or inconclusive information about the localisation of the epileptogenic tissue. Current electroencephalographic (EEG) transients such as epileptic spikes are imperfect markers for the localisation of the surgical target showing a low level of concordance between the brain regions generating spikes and the epileptogenic zone. In the last few years, pathological high-frequency oscillations (HFOs) have demonstrated to be a more reliable marker to detect and delineate regions capable of generating spontaneous seizures. Thus, it has been hypothesised that HFOs could also be used to differentiate between clinically-relevant epileptic spikes confined to regions of seizure onset and propagated spikes that reflect non-specific interictal activity distant to the seizure focus. To test this hypothesis, in this investigation, we explored the use of spikes with concurrent HFOs for the non-invasive localisation of the epileptogenic tissue.

The overarching aim of this research was to investigate the differences of the electrical topological patterns of two clinically different types of epileptic spikes in patients with focal drug-resistant epilepsy (study 1) and to study their neural correlate, using simultaneous EEG and functional magnetic resonance imaging (EEG-fMRI), to assess the clinical concordance of each type of spike for the localisation of the epileptic focus with standard clinical neuroimaging tests (study 2). Additionally, to investigate that our findings were exclusive to patients with focal epilepsy, we examined the occurrence of patient-specific scalp voltage patterns and their respective neural correlates in a group of healthy volunteers (study 3).

Overall the results revealed that (1) HFOs with spikes are pathological and not physiological oscillations, (2) the haemodynamic response of red and green spikes is similar in terms of strength and spatial distribution; and (3) the neural correlate may reflect a combination of primary generation and propagation of the interictal activity that limit the differentiation between haemodynamic changes of each type of spike. Also, activations and deactivations associated with the spatial correlation with the spikes with concurrent HFOs are unique to patients with focal drug-resistant epilepsy and are not seen in healthy individuals, reflecting the involvement of a pathology-specific epileptic network associated with the occurrence of spikes with concurrent HFOs.

About CAI Seminar Series

The perfect opportunity to attend cutting-edge research presentations involving CAI researchers or collaborators, each Tuesday at 9:30am in the CAI Seminar Room, entry via CAI main doors, facing Wep Harris oval (see map).

If you would like weekly email notification for the seminar series or are interested in presenting, please contact CAI Enquiries.

*Our seminar series is now online! See our listed sessions to read more about our upcoming webinars.
To watch previous sessions, press the button below.

CAI Seminar Recordings

Venue

Building 57
The University of Queensland
St Lucia
Room: 
Level 2 Seminar Room