O-44 Clinical validation of criteria for identification of epileptiform EEG discharges in sensor and source space

Abstract

Background Presence of Epileptiform Discharges (ED) in EEG recordings are highly associated with an epilepsy diagnosis. The International Federation of Clinical Neurophysiology (IFCN) suggested 6 criteria in EEG sensor-space, so that presence of at least 4 of them defines a waveform as ED. The aim of our study to assess inter-rater agreement (IRA) and accuracy of identifying spikes in sensor space (using the IFCN criteria at different thresholds) and in source space. Methods EEG samples from 100 consecutive patients with epilepsy and non-epileptic paroxysmal events were reviewed separately in sensor-space and source-space, in different, randomized order, by 7 raters, who scored the presence/absence of each IFCN-criterion in sensor-space, and presence/absence of EDs in source-space. EDs were defined in sensor-space using different thresholds (2–6 criteria) and without counting criteria. Accuracy was determined for each rater and for the majority decisions for each sample. Material and results IRA was moderate both in sensor space and in source space (k: 0.49–0.60). In sensor-space, the highest accuracy (91%) and sensitivity (96%) was achieved using a threshold of 4 criteria. However, this gave a specificity that was lower than acceptable for EEG (85%). Using a threshold of 5 criteria in sensor-space specificity of 96% was achieved, at a sensitivity of 83% and accuracy of 89%. Results in source-space were identical to using the threshold of 5 criteria in sensor-space. Conclusions Using a threshold of 5 IFCN-criteria in sensor-space, and using source-space yields a high specificity and acceptable sensitivity for identifying EDs.