Benign Familial Neonatal Epilepsy

Benign familial neonatal epilepsy (BFNE) is a rare genetic epilepsy syndrome characterized by the occurrence of afebrile seizures in otherwise healthy newborns with onset in the first few days of life.

Epidemiology

Prevalence is currently unknown since this disorder is possibly overlooked. About 100 families have been reported to date.

Clinical description

Seizure onset is usually between the second and the eighth day of life, in otherwise healthy newborns. Seizures are mostly focal involving alternatively both sides of the body and apnea is frequently associated. Seizures can be isolated or in clusters, are generally brief and last 1-2 minutes. However, they can be very frequent, occurring up to 20 times a day, and may evolve into status epilepticus. Seizures can occur during wakefulness and/or sleep, and are of a mixed type, starting with tonic posture and apnea, and often progressing to clonic movements and motor automatisms. During the interictal period, neonates are neurologically normal, although some degree of sedation can be seen in response to anti-epileptic medications. Although most patients do receive antiepileptic treatment in the neonatal period, seizures have been shown to remit spontaneously after the first months of life, and are usually not seen after the first year of life. However, about 10 to 15% of patients have febrile or afebrile seizures later in childhood. Subsequent psychomotor development is normal.

Etiology

BFNE is a genetically heterogeneous disorder due to mutations in the KCNQ2 (20q13.33) and KCNQ3 (8q24) genes that both code for voltage-gated potassium channel subunits. Mutations in KCNQ2 are also responsible for KCNQ2-related epileptic encephalopathy, a severe form of neonatal epilepsy.

Diagnostic methods

Electroclinical events are suggestive of the disorder. Asymmetric tonic posturing associated with apnea and followed by focal or bilateral clonic jerking is the typical seizure type. In BFNE, neonates are neurologically normal and neurocognitive development is normal. Ictal electroencephalogram (EEG) may show focal interictal abnormalities, mainly over the central regions, but otherwise the EEG background is normal. The diagnosis is confirmed by genetic testing.

Differential diagnosis

Differential diagnosis includes benign familial neonatal-infantile seizures and benign familial infantile epilepsy.

Antenatal diagnosis

Prenatal diagnosis is possible if the disease-causing mutation has already been identified in the family.

Genetic counseling

Transmission is autosomal dominant with incomplete penetrance. Genetic counseling should be offered to affected families informing them of the 50% risk the offspring has of inheriting the disease-causing mutation and therefore being affected with the disorder. Rare cases are due to de novo mutations.

Management and treatment

The use of anticonvulsant therapy (e.g. phenobarbital, phenytoin, valproate, carbamazepine) is needed in most cases to stop seizures in the neonatal period, particularly in cases with very frequent seizures or status epilepticus. Usually, patients require treatment for the first 6-12 months of life. However, it is important for clinicians and family to be aware that some patients require treatment beyond 12 months of age.

Prognosis

Prognosis is good. Seizures normally disappear during the first year of life and patients do not display any neurological sequelae. Later seizures have been reported, including occasional febrile seizures and idiopathic epilepsy syndromes in childhood, in particular Rolandic epilepsy.