The EEG diagnosis of NCSE: Concordance between clinical practice and Salzburg Criteria for NCSE

Purpose: To evaluate the concordance between the EEG diagnosis of non-convulsive status epilepticus (NCSE) made by the treating physician and the application of the Salzburg Consensus Criteria (SCC) on consecutive urgent EEG requested for acute alteration of consciousness not otherwise explained.

Methods: Retrospective evaluation of all urgent EEGs acquired between January 1st and March 31st 2018 in adolescents and adult patients (≥14 years old). The 'reference' was the neurologist who first evaluated the patient and reported the corresponding EEG diagnosis. All were blind to the SCC. All included EEG were evaluated and classified by three neurologists trained in the application of SCC blind to the clinical diagnosis.

Results: 181 consecutive EEGs entered the study. The treating clinician diagnosed a NCSE in 17 cases (9%). According to the SCC, 12 EEGs were classified as Definite NCSE (7%), 71 (39 %) as Possible NCSE, and 98 (54 %) as no NCSE. A perfect concordance was found for the Definite- and No-NCSE categories, while only 5 patients with a Possible-NCSE were diagnosed by the treating clinician as having NCSE. It is relevant to note that aamong the 66 patients with a Possible NCSE not diagnosed as SE by the treating clinician, only two presented an evolution toward a definite SE.

Conclusion: SCC have optimal performances for the 'Definite NCSE', and to exclude the presence of a NCSE. Conversely, the Possible NCSE category is still a a grey land of debate that could potentially include many different conditions.