Prolonged postictal deficit: Uncomplicated Todd's palsy or nonconvulsive status epilepticus?

OBJECTIVE: Postictal deficits are a well-recognized phenomenon, yet their mechanisms and predictors remain poorly understood. Distinguishing postictal deficits from recurring nonconvulsive seizures (NCSz) or nonconvulsive status epilepticus (NCSE), their main differential diagnosis, can be challenging. This study aimed to identify clinical and electrographic features predictive of ongoing or recurrent ictal activity and to explore biomarkers associated with the duration and severity of postictal deficits. METHODS: We conducted a retrospective case-control study of patients with prolonged (>1 h) postictal deficits at a tertiary medical center between 2017 and 2022. Based on electroencephalographic (EEG) findings, patients were classified as having uncomplicated Todd's palsy or recurring NCSz. Clinical, imaging, and electrographic characteristics were compared between groups, and factors associated with postictal duration were analyzed. RESULTS: Among 112 patients, 86 (77%) had uncomplicated Todd's palsy and 26 (23%) had recurring NCSz. Patients with NCSz were younger (63 vs. 76 years, p = .022) and had longer deficits (2.5 vs. 1.5 days, p = .024). Sporadic epileptiform discharges (73% vs. 22%, p < .001) and rhythmic or periodic discharges on the ictal-interictal continuum (50% vs. 16%, p = .001) were significantly more frequent in the NCSE group, even when limited to short EEGs or the first 30 min of continuous EEG (96% vs. 40%, p < .001). Consequently, 2HELPS2B scores were higher in NCSE patients (2 vs. 1, p = .0065). In the uncomplicated Todd's palsy group, a preceding focal to bilateral tonic-clonic seizure (1.5 vs. 1.0 days, p = .04) and any rhythmic or periodic discharges on EEG (3.0 vs. 1.5 days, p = .003) were associated with longer deficit duration. SIGNIFICANCE: A notable minority of patients with prolonged postictal deficits have recurring NCSz. In the absence of reliable clinical or imaging predictors, patients with prolonged deficits may benefit from a 30-min EEG followed-when 2HELPS2B score > 1-by extended continuous EEG monitoring.