Only 50 families have been described.
Age at onset
First week of life, mainly on the second or third day.
Males = females.
Neurological and mental state
Channelopathy of an autosomal dominant pattern of inheritance and 85% degree of penetrance. It is caused by mutations in the voltage-gated potassium channel subunit gene KCNQ2 on chromosome 20q13.3 and KCNQ3 on chromosome 8q24. Mutations in either KCNQ2 or KCNQ3 can produce the same phenotype.
Seizures mainly occur in full-term normal neonates after a normal pregnancy and delivery and without precipitating factors. Seizures are brief, usually 1 to 2 min, and may be as frequent as 20 to 30 per day. Most seizures start with tonic motor activity and posturing with apnea followed by vocalizations, ocular symptoms, other autonomic features, motor automatisms, chewing, and focal or generalized clonic movements. The clonic components of the later phase are usually asymmetrical and unilateral. The post-ictal state is brief. Inter-ictally the neonates are normal. Pure clonic or focal seizures are considered rare.
All relevant tests applied for neonatal seizures are normal.
May be normal, discontinuous, or have focal or multifocal abnormalities or 'théta pointu alternant' pattern. It is of limited value, although it may exclude symptomatic neonatal seizures.
Onset with synchronous and bilateral flattening lasting from 5 to 19 sec and coinciding with apnea and tonic motor activity. This is followed by bilateral and often asymmetrical discharges of spikes and sharp waves for 1 to 2 min, which coincide with vocalizations, chewing, and focal or generalized clonic activity.
Usually good. Seizures remit between 1 and 6 months from onset. 10% to 14% may later develop other types of febrile (5%) or heterogeneous non-febrile seizures (mostly idiopathic generalized seizures). The risk of epilepsy depends on whether other affected relatives developed a seizure disorder later in life. Normal development occurs.
A family history of similar convulsions eliminates the possibility of other diseases. Other causes of neonatal seizures should be excluded.
Benign familial neonatal seizures are entirely different from benign neonatal seizures (non-familial).
Anti-epileptic medication does not influence prognosis. Prolonged seizures may be terminated with benzodiazepines.
This section was adapted from: The educational kit on epilepsies, The epileptic syndromes By C. P. Panayiotopoulos Originally published by MEDICINAE 21 Cave Street, Oxford OX4 1BA First published 2006 and reprinted in 2007