Benign familial neonatal convulsions (BFNC) and benign nonfamilial neonatal convulsions (BNFNC) should be suspected in healthy-looking neonates with no interictal neurological deficit. These syndromes should be considered only after excluding benign nonepileptic paroxysmal motor events such as benign neonatal sleep myoclonus and behavioral movements, etiological-treatable seizures such as those due to sepsis and hypoglycemia, and more frequent causes of neonatal seizures associated with normal interictal neurological examinations such as subarachnoid bleed and hypocalcemia.

ETIOLOGY

The first description of BFNC was made by Rett and Teubel in 1964.¹ BFNC has an autosomal dominant mode of inheritance in most cases, but autosomal recessive and sporadic cases have been reported.² Patients with autosomal dominant BNFC have mutations in the two homologous genes: KCNQ2 (chromosome 20q) and KCNQ3 (chromosome 8q). These genes encode a subunit of the M-type voltage-gated potassium channel.³ The autosomal recessive type of BFNC is associated with mutations of the sodium channel subunit gene SCN2A (chromosome 2q). In the later condition, some family members have neonatal-onset seizures whereas other members of the family have infancy-onset seizures.^4,5,6 Sporadic cases probably represent de novo mutations in the KCNQ2, KCNQ3, or SCN2A genes.

CLINICAL PRESENTATION

In patients with BFNC, seizures usually start between 2 and 15 days of birth, but most patients start having seizures at 2 or 3 days of age. Seizures tend to occur during sleep and are usually clonic. They may be focal or generalized. Generalized seizures tend to be asymmetrical due to immaturity of the corpus callosum. Seizures may be associated with apnea, vocalization, or chewing movements. The number of seizures during the first 2–3 months of age varies from a few to several dozen per day. The frequency of the episodes decreases during the following months and they are no longer present by 6 months of age.^2,7,8

EEG FINDINGS

The interictal EEG is normal or may show minimal focal or multifocal abnormalities. A characteristic pattern named Theta Pointu Alternant has been reported, but it is not as frequently encounter as in benign idiopathic neonatal convulsions.⁷ The ictal EEG consists of bilateral, symmetrical flattening for a few seconds followed by bilateral spikes and sharp waves discharges lasting for 1–2 minutes. This ictal pattern has led the authors to conclude that the convulsions of benign neonatal familial convulsions are a form of generalized seizure disorder.⁸ Yet other authors consider the BNFC, a form of partial seizure disorder, based on their clinical manifestations.⁹

DIAGNOSIS

The clinical diagnosis of BNFC requires: (1) a family history of neonatal seizures in neurologically normal direct relatives, (2) a benign neonatal course, and (3) spontaneous cessation of seizures by 6 months of age.² Hence, the clinical diagnosis of BNFC cannot be made during the neonatal period. The diagnosis of BNFC can only be established in the neonatal period by detecting the gene mutations in KCNQ2, KCNQ3, or SCN2A. These mutations can be detected by using sequencing or multiplex ligation-dependent probe amplification.⁴

PROGNOSIS

The prognosis of BFNC is good. BFNC are not associated with mental retardation. The rate of febrile seizures in patients with BNFC is similar to the general population. Central temporal (rolandic) EEG foci without clinical manifestation have been reported in the follow-up of a few patients. Epilepsy occurs in 11%–14% of cases of BNFC.^2,10,11,12