The EEG pattern marked C—continuous spike-wave of sleep (CSWS), also called electrical status epilepticus in sleep (ESES)—is a rare age-related epileptic encephalopathy with onset typically between 3–10 years. The hallmark is a spike-wave index (SWI) >85% during non-REM sleep. The clinical presentation of global cognitive regression, behavioral deterioration, and seizures in a previously normal child with this EEG pattern is pathognomonic for CSWS. The mechanism involves disruption of sleep-dependent memory consolidation and synaptic homeostasis by near-continuous nocturnal epileptiform activity. According to Nelson Pediatrics 21e and the Epilepsia 2009 CSWS consensus, high-dose corticosteroids (prednisolone or ACTH) or valproate are the established first-line treatments. Early aggressive therapy is essential because cognitive sequelae often persist if treatment is delayed.
Nelson Pediatrics 21e; Epilepsia 2009 CSWS consensus
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