EEG interpretation reliability and interpreter confidence: a large single-center study.

The intrarater and interrater reliability (I&IR) of EEG interpretation has significant implications for the value of EEG as a diagnostic tool. We measured both the intrarater reliability and the interrater reliability of EEG interpretation based on the interpretation of complete EEGs into standard diagnostic categories and rater confidence in their interpretations and investigated sources of variance in EEG interpretations. During two distinct time intervals, six board-certified clinical neurophysiologists classified 300 EEGs into one or more of seven diagnostic categories and assigned a subjective confidence to their interpretations. Each EEG was read by three readers. Each reader interpreted 150 unique studies, and 50 studies were re-interpreted to generate intrarater data. A generalizability study assessed the contribution of subjects, readers, and the interaction between subjects and readers to interpretation variance. Five of the six readers had a median confidence of ≥99%, and the upper quartile of confidence values was 100% for all six readers. Intrarater Cohen's kappa (κc) ranged from 0.33 to 0.73 with an aggregated value of 0.59. Cohen's kappa ranged from 0.29 to 0.62 for the 15 reader pairs, with an aggregated Fleiss kappa of 0.44 for interrater agreement. Cohen's kappa was not significantly different across rater pairs (chi-square=17.3, df=14, p=0.24). Variance due to subjects (i.e., EEGs) was 65.3%, due to readers was 3.9%, and due to the interaction between readers and subjects was 30.8%. Experienced epileptologists have very high confidence in their EEG interpretations and low to moderate I&IR, a common paradox in clinical medicine. A necessary, but insufficient, condition to improve EEG interpretation accuracy is to increase intrarater and interrater reliability. This goal could be accomplished, for instance, with an automated online application integrated into a continuing medical education module that measures and reports EEG I&IR to individual users.

Sutton's law in epilepsy: because that is where the lesion is.

Successful epilepsy surgery requires unambiguous identification of the epileptogenic zone. This determination may be a challenge when the pre-surgical evaluation yields conflicting data. We evaluated an adult patient with a right insular mass, but a seizure semiology, interictal EEG, and ictal EEG, suggesting left temporal lobe epilepsy. Resection of the mass, a ganglioglioma, resulted in seizure freedom and disappearance of interictal left temporal lobe epileptiform discharges. This case illustrates the principle that in localization-related epilepsy, the money is usually in the mass.

Clinical characteristics of psychogenic nonepileptic seizure status in the long-term monitoring unit.

Patients with psychogenic nonepileptic seizures (PNES) mimicking status epilepticus (PNES-status) are at risk of iatrogenic complications. Our aim was to assess whether the population of patients with PNES who develop PNES-status are distinguishable. Retrospectively, we identified patients with PNES-status and compared them with patients with PNES without status and with patients with electroclinical status epilepticus (SE). Of 49 patients with PNES, 9 had PNES-status (18.2%) and 40 had PNES only. Compared with patients with PNES, subjects with PNES-status had taken fewer than three antiepileptic medications (P=0.016), had more than one event per week (P=0.026), were more likely to be admitted emergently to the monitoring unit (P=0.007), had shorter long-term monitoring (LTM) stays (P=0.003), and tended to be diagnosed sooner after initial presentation (P=0.058). Use of fewer than three antiepileptic drugs and emergent admission were independent predictors of PNES-status classification on logistic regression. Of 154 patients with epilepsy, 8 had SE during LTM (5.2%), significantly fewer than the proportion with PNES-status relative to PNES (P=0.008); the only clinical variable distinguishing these two groups was a baseline lower seizure frequency among the patients with epileptic seizures (P=0.045). Our results suggest that patients with PNES-status have features that differentiate them from patients with PNES without status and, to a lesser extent, from patients with epileptic seizures.