Characteristics of overnight video-EEG monitoring in infantile epileptic spasms syndrome at 2-week follow-up.

Objective: To determine the optimal duration of electroencephalography (EEG) recording to detect epileptic spasms (ES) based on inpatient overnight video-EEG monitoring in patients with infantile epileptic spasms syndrome (IESS) at the 2-week follow-up.

Methods: Patients with IESS and overnight EEG monitoring between January 2020 and June 2022 were retrospectively reviewed. Time-to-ES, time-to-sleep and time-to-epileptic encephalopathy (EE) per the Burden of Amplitudes and Epileptiform Discharges (BASED 2021) score. BASED 2021 score were reported. ES and sleep detection sensitivity were calculated with respect to monitoring time. Etiology, treatment, and EEG features were assessed for strength of association with continued ES. Time-to-event analysis was performed with the first ES as the event of interest.

Results: Of 90 patients, 39 (43%) continued to have ES; 78.6% with EE continued to have ES, whereas only 27.4% without EE had ES (odds ratio [OR] 12.05). Structural etiologies were also associated with continued ES (OR 5.24). ES detection was 35.9%, 76.9%, and 84.6% at 1, 4, and 6 h, respectively, with corresponding negative likelihood ratios (NLRs) of .64, .23, and .15. ES detection reached >90% and >95% at 14 and 19 h, respectively. Sleep detection was 52.2%, 84.4%, and 95.6% at 1, 4, and 6 h, respectively, and captured in all patients by 11 h. EE was observed by 6 h for all associated patients.

Significance: Typical routine EEG durations (<1 h) were not sufficient to detect ES, EE, or sleep in patients with IESS at the 2-week follow-up. Four hour outpatient EEG will capture ES in 77% and sleep in 84% of the patients. EE, if present, was shortly after sleep onset. Additional monitoring of up to 19 h was needed to capture >95% of patients with ES. Although EE was strongly associated with continued ES, 27.4% of patients without EE demonstrated ES. This study will help guide adequate duration of EEG monitoring at the 2-week follow-up for patients with IESS.