Developmental and/or epileptic encephalopathy with spike-and-wave activation in sleep: Pathophysiological insights and treatment options.

Developmental and/or epileptic encephalopathy with spike-and-wave activation in sleep (D/EE-SWAS) represents a rare but severe group of childhood onset epilepsies characterized by sleep-potentiated epileptiform activity, seizures, and developmental stagnation or regression affecting cognition, language, and behavior. Once considered a self-limited electroencephalographic (EEG) phenomenon, D/EE-SWAS is now recognized as a disorder of brain network dysfunction in which persistent epileptiform discharges during non-rapid eye movement sleep disrupt synaptic plasticity, sleep-dependent memory consolidation, and neurodevelopmental trajectories. This review synthesizes recent advances in clinical phenotyping, genetics, neurophysiology, and therapeutics. Etiologically, D/EE-SWAS is highly heterogeneous, with pathogenic variants identified in nearly half of affected individuals, including copy number variants and single-gene disorders involving ion channels, synaptic proteins, and transcriptional regulators. GRIN2A is the most frequently implicated gene, although marked intrafamilial and interfamilial variability underscores the role of modifying genetic and network-level factors. Structural lesions-particularly those affecting thalamocortical circuits-represent another major disease substrate and are critical for treatment stratification. At the mechanistic level, abnormal thalamocortical oscillations, impaired sleep architecture, and disruption of slow-wave and spindle activity provide a pathophysiological framework linking EEG abnormalities to cognitive and behavioral deterioration. Neuroimaging and EEG-functional magnetic resonance imaging studies support a model of widespread network inhibition and disconnection extending beyond the primary epileptogenic zone. Therapeutically, corticosteroids currently represent the most effective first-line treatment, demonstrating superior cognitive outcomes compared with benzodiazepines, although relapse after tapering is common, and optimal dosing strategies remain undefined. Precision medicine approaches, including N-methyl-D-aspartate receptor-targeted therapies for GRIN variants and channel-specific treatments such as primidone for TRPM3 gain of function, offer promising avenues toward disease modification. Epilepsy surgery should be considered early in children with unilateral structural etiologies, where it can provide substantial neurodevelopmental benefit. Future priorities include standardized outcome measures, integration of sleep-based biomarkers, refinement of steroid protocols, and international collaborative trials to improve long-term neurodevelopmental outcomes in this vulnerable population.