GTR Home > Conditions/Phenotypes > Benign familial neonatal seizures 2

Disease characteristics

Excerpted from the GeneReview: KCNQ2-Related Disorders
KCNQ2-related disorders represent a continuum of overlapping neonatal epileptic phenotypes caused by a heterozygous mutation in KCNQ2. The clinical features of KCNQ2-related disorders range from KCNQ2-related benign familial neonatal epilepsy (KCNQ2-BFNE) at the mild end to KCNQ2-related epileptic encephalopathy (KCNQ2-NEE) at the severe end. KCNQ2-BFNE is characterized by a wide spectrum of seizure types (tonic or apneic episodes, focal clonic activity, or autonomic changes) that start in otherwise healthy infants between the second and eighth day of life and spontaneously disappear between the first and the sixth to 12th month of life. Motor activity may be confined to one body part, migrate to other body regions, or generalize. Seizures are generally brief, lasting one to two minutes. Rarely, KCNQ2-BFNE may evolve into status epilepticus. About 10%-15% of individuals with BFNS develop epileptic seizures later in life. KCNQ2-NEE is characterized by multiple daily seizures beginning in the first week of life that are mostly tonic, with motor and autonomic features. Seizures cease between ages nine months and four years. At onset, EEG shows a burst-suppression pattern or multifocal epileptiform activity; early brain MRI shows basal ganglia and thalamic hyperintensities that later resolved. Most affected individuals are profoundly intellectually impaired and have axial hypotonia and/or spastic quadriplegia.

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Clinical features

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  • Generalized tonic-clonic seizures
  • Focal clonic seizures

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