Intracerebrally recorded high frequency oscillations: Simple visual assessment versus automated detection

• Simple visual assessment of SEEG traces (filtered in frequency ranges 80–200 Hz and 200–450 Hz) and standard automated detection of HFO contribute comparably (similar sensitivity) to the identification of the SOZ in subjects with focal epilepsies.
• Fully automated detection of HFO enables the objective evaluation of whole data without any bias from the neurophysiologist’s experience.
• When using macroelectrodes in neocortical extratemporal epilepsies, the SOZ might be better determined (higher specificity) by the ripple range than by fast ripples.

ObjectiveWe compared the possible contribution (in the detection of seizure onset zone – SOZ) of simple visual assessment of intracerebrally recorded high-frequency oscillations (HFO) with standard automated detection.MethodsWe analyzed stereo-EEG (SEEG) recordings from 20 patients with medically intractable partial seizures (10 temporal/10 extratemporal). Independently using simple visual assessment and automated detection of HFO, we identified the depth electrode contacts with maximum occurrences of ripples (R) and fast ripples (FR). The SOZ was determined by independent visual identification in standard SEEG recordings, and the congruence of results from visual versus automated HFO detection was compared.ResultsAutomated detection of HFO correctly identified the SOZ in 14 (R)/10 (FR) out of 20 subjects; a simple visual assessment of SEEG recordings in the appropriate frequency ranges correctly identified the SOZ in 13 (R)/9 (FR) subjects.ConclusionsSimple visual assessment of SEEG traces and standard automated detection of HFO seem to contribute comparably to the identification of the SOZ in patients with focal epilepsies. When using macroelectrodes in neocortical extratemporal epilepsies, the SOZ might be better determined by the ripple range.SignificanceStandard automated detection of HFO enables the evaluation of HFO characteristics in whole data. This detection allows general purpose and objective evaluation, without any bias from the neurophysiologist’s experiences and practice.