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A newborn has frequent seizures starting on day 2 of life. Seizures are brief tonic events. By 3 months, seizures have resolved. Development is normal at follow-up.
AD; KCNQ2 (potassium channel)
- Benign familial neonatal epilepsy (BFNE): self-limited, normal development
- KCNQ2 encephalopathy: neonatal seizures, developmental impairment
- Molecular testing of KCNQ2 (epilepsy gene panel or exome) in neonatal-onset seizures, after excluding metabolic and structural causes
- EEG and brain MRI characterize seizures and exclude acquired causes; the encephalopathic form often shows a burst-suppression or multifocal EEG
- Variant type guides phenotype: loss-of-function variants tend toward benign familial neonatal epilepsy, while certain missense (often gain-of-function) variants cause the encephalopathy
- Parental testing distinguishes inherited (benign familial) from de novo (often encephalopathy) variants; cascade testing and reproductive counseling once a variant is found (autosomal dominant)
- Sodium-channel blockers (carbamazepine, oxcarbazepine, phenytoin) are often effective, including in KCNQ2 encephalopathy
- Benign familial neonatal epilepsy is self-limited; seizures usually resolve within months and medication can often be weaned
- KCNQ2 encephalopathy needs developmental surveillance and early intervention for the associated impairment
- Counsel families on prognosis, which differs markedly between the benign and encephalopathic forms
"KCNQ2 seizures Quit by age 2": In the benign form (BFNE), neonatal seizures typically self-resolve within the first few months of life and respond well to medications (vs Dravet syndrome, which is drug-resistant).