Benign familial neonatal seizures type 1 (BFNS1) is a rare autosomal dominant disorder characterized by generalized or focal tonic-clonic seizures that occur in the first days of life. These seizures usually remit spontaneously within a year. For affected individuals psychomotor development is usually normal but 10-15% of these individuals develop epileptic seizures later in life. Also, therapy-resistant epileptic encephalopathy associated with variable cognitive delays and myokymia may rarely occur.
Diagnosis is based on symptoms with no specific EEG findings in the majority of patients. The disorder is distinguished from benign familial infantile seizures by an earlier age at onset. Neonatal seizures are usually controlled with phenobarbiturate, but in some patients other antiepileptic drugs are required.
BFNS1 is caused by mutations in the KCNQ2 (KQT-like subfamily, member 2) gene. KCNQ2 encodes alpha-subunits of the potassium voltage-gated Kv7.2 channels, which are present in higher numbers at axonal initial segments and at nodes of Ranvier in the central nervous system. Mutations in KCNQ2 disrupt the regulation in the subthreshold electrical excitability of many neurons leading to seizures.
