HFOs identified by machine learning methods consistently correlate with the epileptic foci in adult and pediatric patients
Compared to epilepsy literature, the fields of high frequency oscillations and the related detection techniques are in their infancy states. Few reports have capitalized on the prognostic role of HFO captured by automatic detection in the localization of SOZ. The functional use of HFO auto-detection in clinical practice is poorly documented.
In order to fill this gap, in this project the HFOs identified by the proposed three-stage automatized technique were utilized as spatial markers to the epileptic seizure onset regions in the brain. The relationship among interictal spikes and presumed discrete sub-groups of HFOs discovered by the algorithm were explored, and the spatial distribution of HFOs were compared with the clinician delineated SOZ in representative unique cases, to assess the value of these neuronal events in SOZ approximation using data collected in real clinical environment.
Case example: HFOs in Epilepsy Associated with Cavernous Malformation.
The HFO mapping results (upper) estimated from 30-min ECoG segments consistently highlighted the perilesional region of the CM, regardless of the day of recording, whereas during the monitoring period, spike channels shifted anteriorly and inferiorly surrounding the CM (lower). The distribution also changed through the sleep-wake cycle.
In another case example, interictal ripples in 80 – 200 Hz range were automatically captured and identified as two sub-groups. The detected HFOs were spatially correlated with seizure onset regions identified by neurologists (left), as well as the functional sites indicated by anatomical landmarks or direct cortical stimulation (right).
In a third example, we investigated the HFO characteristics in a patient with uncontrollable frontal lobe seizures caused by brain tumor. Notably, a considerable proportion of HFOs (left) were discovered outside the resection zone (yellow line) from a more distant area . By contrast, most of the spikes were located within the tumor area inside the resection border. Postsurgical evaluation indicated that the patient received limited improvement in seizure frequency (Engel Class III), although the majority of spike generating sites have been surgically removed