Among 144 patients with self-limited focal epilepsies of childhood, 8.3% evolved into spike-and-wave activation in sleep (SWAS), with the majority also developing cognitive or behavioral regression consistent with epileptic encephalopathy.
Key Findings
Results
A minority but clinically significant proportion of patients with self-limited focal epilepsies of childhood (SeLFE) evolved into spike-and-wave activation in sleep (SWAS).
12 out of 144 patients (8.3%) with SeLFE developed SWAS during follow-up
The cohort included 57 (39.6%) with SeLECTS, 65 (45.1%) with SeLEAS, and 22 (15.3%) with COVE
SWAS was defined as spike and wave discharges occupying ≥50% of NREM sleep with symmetrical or mildly asymmetrical bilateral or unilateral hemispheric distribution
Study design was retrospective with a minimum 2-year follow-up, at least two awake and sleep EEGs, and patients diagnosed per ILAE 2022 criteria
Results
SWAS evolution was distributed across all three SeLFE subtypes, with SeLEAS contributing the most cases.
5 of 57 SeLECTS patients evolved into SWAS
6 of 65 SeLEAS patients evolved into SWAS
1 of 22 COVE patients evolved into SWAS
Mean age of seizure onset was 7.6 years for SeLECTS, 5.6 years for SeLEAS, and 8.5 years for COVE
Results
The time from first seizure to evolution into SWAS varied considerably across patients and subtypes.
Overall time from first seizure to SWAS ranged from 5.2 to 75 months, with a mean of 26.8 ± 19.8 months
For SeLECTS patients, the range was 6.2–42.8 months (mean: 20.1 ± 14.7 months)
For SeLEAS patients, the range was 5.2–75.0 months (mean: 32.7 ± 24.5 months)
The single COVE patient evolved at 25.0 months
Results
The majority of patients who evolved into SWAS also developed cognitive or behavioral regression, meeting criteria for epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS).
All except two patients who developed SWAS also had cognitive or behavioral regression
These patients were diagnosed with epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS)
One patient was diagnosed with Landau-Kleffner syndrome
Two patients developed SWAS without apparent cognitive or behavioral regression
Conclusions
The authors highlight that SeLFEs are no longer recognized as 'benign' epilepsies under the most recent ILAE classification, and clinicians should remain vigilant about SWAS risk.
The ILAE 2022 diagnostic criteria no longer classify SeLFEs as 'benign' epilepsies
The authors state that 'even with a low incidence rate, clinicians should always be cautious about the risk of SWAS development in these syndromes'
The study period spanned from 1989 to 2023, representing over three decades of clinical follow-up at a single center
What This Means
This research examined a group of 144 children with a category of epilepsy called self-limited focal epilepsies of childhood (SeLFE), which includes three specific syndromes previously thought to be relatively harmless because most children outgrow them. The study tracked these children over time and found that about 1 in 12 (8.3%) developed a more serious EEG pattern during sleep called spike-and-wave activation in sleep (SWAS), where abnormal brain electrical activity occupies at least half of non-dreaming sleep. This transition could happen anywhere from about 5 months to over 6 years after the first seizure, meaning the risk persists over a long period.
Among the children who developed this sleep-related brain activity pattern, nearly all also showed signs of cognitive or behavioral decline, which is the hallmark of a more serious condition called epileptic encephalopathy. One child developed Landau-Kleffner syndrome, a rare condition involving loss of language skills. The findings span all three subtypes of SeLFE studied, suggesting that no subtype is entirely free from this risk.
This research suggests that doctors should not assume these childhood epilepsies are automatically benign, and that ongoing monitoring with sleep EEGs may be warranted even in children who initially seem to be doing well. The international epilepsy organization (ILAE) has already updated its guidelines to drop the word 'benign' from the classification of these epilepsies, and this study provides real-world data supporting the importance of that change. Regular follow-up and awareness of potential cognitive changes in children with these diagnoses appears clinically important.
İriş M, Yaşgüçlükal M, Yalçınkaya C, Demirbilek V. (2026). Evolution into spike-and-wave activation in sleep in patients with self-limited focal epilepsies.. Seizure. https://doi.org/10.1016/j.seizure.2026.01.006