Benign Familial Infantile Epilepsy

Benign familial infantile epilepsy (BFIE) is a genetic epileptic syndrome characterized by the occurrence of afebrile repeated seizures in healthy infants, between the third and eighth month of life.

Epidemiology

Although BFIE cases have been reported worldwide, prevalence and incidence remain unknown. In an Argentinian case series, BFIE have been listed as the third most common type of epilepsy in the first two years of life.

Clinical description

Seizures usually occur between 3 to 8 months of life, with clusters (8-10 a day) of repeated and brief episodes (2-5 minutes) over a few days. They are usually focal but can sometimes become generalized. Patients present with motor arrest, unresponsiveness, head and/or eye deviation to one side, staring, fluttering of eyelids, grunting, cyanosis, diffuse hypertonia and unilateral or bilateral clonic jerks of the limbs. During the interictal period, patients regain full consciousness and activity. Psychomotor development is normal. A family history of the same epilepsy is a constant finding. A syndrome called familial infantile convulsions and choreoathetosis (ICCA; see this term) has been observed in which BFIE patients present in childhood and/or adolescence with choreoathetotic dyskinetic attacks occurring spontaneously or following diverse stimuli (e.g. exercise, stress). In some rare cases, BFIE has been associated with familial or sporadic hemiplegic migraine.

Etiology

BFIE is a genetically heterogeneous disease. In the majority of cases, mutations in the proline-rich transmembrane protein 2 (PRRT2) gene located at 16p11.2 have been found. This gene encodes a membrane protein that interacts with the presynaptic protein SNAP-25. Mutations have also been found in the SCN2A gene (2q24.3) encoding the brain sodium channel NaV1.2 and rarely in the KCNQ2 (20q13.33) and KCNQ3 (8q24) genes both encoding potassium channels. Additionally, three other chromosomal loci have been identified that are mapped to chromosome 19q, 16p and 1p.

Diagnostic methods

Family history can orient the diagnosis which is based on electroencephalography (EEG) and video recordings. Ictal EEG shows that partial seizures originate from the parietal-occipital region and that the side of the hemisphere involved can vary between episodes. Seizures can sometimes spread and involve the entire brain. During a cluster of seizures, postictal EEG shows lateralized occipito-parietal delta waves and spikes. Outside the cluster, waking and sleeping interictal EEG is normal. Interictal neurological examination and brain imaging (brain CT and/or MRI) are normal. Genetic testing confirms the diagnosis.

Differential diagnosis

Differential diagnosis includes benign familial neonatal-infantile seizures (see this term), an epileptic syndrome with an intermediate onset between the neonatal and infantile age that shares overlapping clinical characteristics with BFIE and that is mainly due to mutations in the SCN2A gene. Other differential diagnoses are benign non-familial infantile seizures, benign infantile seizures associated with mild gastroenteritis and benign infantile focal epilepsy with midline spikes and waves during sleep (BIMSE) (see these terms).

Genetic counseling

BFIE is transmitted as an autosomal dominant trait with incomplete penetrance.

Management and treatment

With anti-epileptic treatment (e.g. carbamazepine, valproate, phenobarbital), symptoms quickly disappear and no other type of epilepsy has been reported to reappear. In patients with a clear familial history the treatment can be interrupted within a few months.

Prognosis

Prognosis is good. Seizures normally disappear after the first year of life and patients do not display any neurological sequelae.