Criteria for defining interictal epileptiform discharges in EEG

Abstract

ObjectiveTo define and validate criteria for accurate identification of EEG interictal epileptiform discharges (IEDs) using (1) the 6 sensor space criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) and (2) a novel source space method. Criteria yielding high specificity are needed because EEG over-reading is a common cause of epilepsy misdiagnosis.MethodsSeven raters reviewed EEG sharp transients from 100 patients with and without epilepsy (diagnosed definitively by video-EEG recording of habitual events). Raters reviewed the transients, randomized, and classified them as epileptiform or nonepileptiform in 3 separate rounds: in 2, EEG was reviewed in sensor space (scoring the presence/absence of each IFCN criterion for each transient or classifying unrestricted by criteria [expert scoring]); in the other, review and classification were performed in source space.ResultsCutoff values of 4 and 5 criteria in sensor space and analysis in source space provided high accuracy (91%, 88%, and 90%, respectively), similar to expert scoring (92%). Two methods had specificity exceeding the desired threshold of 95%: using 5 IFCN criteria as cutoff and analysis in source space (both 95.65%); the sensitivity of these methods was 81.48% and 85.19%, respectively.ConclusionsThe presence of 5 IFCN criteria in sensor space and analysis in source space are optimal for clinical implementation. By extracting these objective features, diagnostic accuracy similar to expert scorings is achieved.Classification of evidenceThis study provides Class III evidence that IFCN criteria in sensor space and analysis in source space have high specificity (>95%) and sensitivity (81%–85%) for identification of IEDs.

Objective interictal electrophysiology biomarkers optimize prediction of epilepsy surgery outcome

“… 19 , 20 Since the present study has chosen to quantify the magnitude of high-frequency amplitude ≥80 Hz stereotypically coupled with subsequent slow-wave 3–4 Hz, MI effectively reflects the severity of spike-and-wave discharges. 21 , 22 Two epilepsy centres independently reported that the phase-amplitude coupling was elevated at the SOZ; thereby, the coupling with slow-wave at 3–4 Hz best differentiated the SOZ from non-SOZ. 23 , 24 We determined whether the standard outcome classification model would be improved by incorporating MI more than consideration of HFO, or vice versa .…”

Temporal Lobe Epilepsy and Alzheimer’s Disease: From Preclinical to Clinical Evidence of a Strong Association

“…When approaching the review of literature about AD and epileptiform activity, there are several limitations hindering comparison among studies: lack of definition of interictal epileptiform abnormalities (IEAs), different electroencephalogram (EEG) techniques used, methods of evaluation of IEAs by different researchers, etc. Criteria for IEAs definition were only recently validated [ 82 ]. In particular, the IEAs are defined as paroxysmal sharp waveforms (di- or tri-phasic waves with sharp or spiky morphology) on EEG, lasting 20 to 200 ms and followed by an associated slow after-wave, that disrupt background activity.…”

“…Later, Vossel and colleagues (2016) [ 12 ] prospectively evaluated subclinical epileptiform activity in 33 AD patients and 19 controls without cognitive impairment through overnight long-term video-EEG and a 1-h resting magnetoencephalography exam with simultaneous EEG. Experienced epileptologists and clinical neurophysiologists reviewed EEG recordings and authors provided an accurate definition of epileptiform activity even if not completely fulfilling the recent criteria [ 82 ]. They detected subclinical epileptiform activity in 42.4%of AD patients and 10.5%of controls and reported its prevalence in temporal lobes and during NREM sleep.…”

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“…A sensibilidade de um único exame de EEG é inferior a 50%, entretanto pode aumentar para 92% no quarto exame. A especificidade do exame, por sua vez, é superior a 90% Desse modo, um EEG normal não exclui o diagnóstico de epilepsia, mas um exame positivo é altamente sugestivo deste diagnóstico 11 .…”