Background: The clinical-EEG profile and prognosis in nonconvulsive status epilepticus (NCSE-coma) - with preceding SE and without preceding SE - have not been fully established yet.

Objective: To evaluate the initial EEG, clinical characteristics, and hospital outcome of older adults with NCSE-coma.

Methods: Clinical variables, immediate prognosis, initial EEG data, and scores on the Status Epilepticus Severity Score (STESS) and the SACE score were evaluated according to the type of NCSE-coma (with and without preceding seizure/SE) in 51 older adult patients treated in the emergency department.

Results: The mean age of the participants was 72.2 years. In 23 cases, the diagnosis was NCSE-coma with preceding seizure/SE, and in 28 cases the diagnosis was NCSE-coma without preceding seizure/SE. Previous history of seizures/epilepsy occurred in 11 cases (21.5 %), and was more frequent in NCSE-coma with preceding seizure/SE. The most common etiology was acute. Death within 30 days occurred in 21 cases (41.1 %), but there was no difference between types of NCSE-coma. The predominant EEG finding was the presence of epileptiform discharges/rhythmic delta activity showing morphological/spatial/temporal evolution (classified as A2 in the Salzburg Consensus Criteria [SCC]). There was a significant difference in EEG findings according to the type of NCSE-coma. Total SACE scores averaged 0.9 ± 0.8; on the STESS, it was 4.7 ± 0.4. In the SACE score, the highest total score and a more significant occurrence of scores ≥ 3 (indicating a better prognosis) were observed in NCSE-coma with preceding seizure/SE.

Conclusions: In older adults, the types of NCSE-coma presented different clinical aspects and patterns on initial EEG. The mortality rates were elevated. The most prevalent EEG findings encompass criteria A2 of the SCC. A history of previous seizures/epilepsy and a more favorable prognosis in the SACE score occurred in NCSE-coma with preceding seizure/SE.