Introduction
Benign familial neonatal convulsion is a condition that causes recurrent seizures in newborn children. Psychomotor development may be normal in full-term or nearly full-term children with benign convulsions. However, the seizures may be brief and frequent.
What Is the Pathophysiology of Benign Familial Neonatal Convulsions?
Benign familial neonatal convulsions are inherited in an autosomal dominant trait. The following may be the pathophysiology of the disease:
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M-type potassium channel mutation.
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Epilepsy predisposition.
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Ion channel dysfunction.
What Are the Synonyms for Benign Familial Neonatal Convulsions?
The synonyms include:
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Benign familial neonatal seizures.
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Benign familial neonatal epilepsy.
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Benign neonatal convulsions.
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Benign neonatal epilepsy.
What Is the Cause of Benign Familial Neonatal Convulsions?
The causes of benign familial neonatal convulsions may involve rotavirus infection, vitamin B12 deficiency, and low central nervous system zinc levels. However, the most accepted cause is the presence of self-limiting dysfunction in voltage-gated or ligand-gated ion channels.
Potassium Channel Dysfunction:
Most affected families with benign familial neonatal convulsions have abnormalities in the genes coding for KCNQ3 and KCNQ2 potassium channels. The dysfunction causes it in only two chromosomes: BFNC1, a locus on band 20q13.3, and BFNC 2 on band 8q24. This defect causes defective repolarization of the neuronal membrane leading to neonatal seizures. But these abnormalities in the neuronal membrane do not cause seizures in the later period of life. This may be the result of homeostasis in the brain. It is believed that the potassium channels get upregulated to compensate for the deficiency in the function of the defective channels.
Defective Neurotransmitter Development:
The infant's brain differs electrophysiologically during early development. Gamma-aminobutyric acid has a paradoxical excitatory effect. Glutamate synapses develop slowly and show delayed expression of the Cl or K ions cotransporter KCC2 and NKCC1. The direct inhibition in the infant's brain is presynaptic. The neuronal membrane homeostasis is maintained along with the postsynaptic excitatory postsynaptic responses and inhibitory postsynaptic potentials when approaching the adult state.
What Is the Epidemiology of Benign Familial Neonatal Convulsions?
Benign familial neonatal convulsions are not rare but not common either, and very few cases have been reported. Underreporting may be the issue. At times, the seizure present during the first few months of birth may resolve as the child grows. The cases are usually reported from parts of Western Europe, China, and Japan. Males and females are affected equally in benign familial neonatal convulsions. Benign familial neonatal convulsions have an onset as early as two days after birth; in some cases, it may take up to several weeks. Other members of the family who are unaffected have a higher risk of developing epilepsy in the later stages of life. Studies have shown that family members of the affected individual have a genetic defect in the potassium channel.
What Is the Prognosis for Benign Familial Neonatal Convulsions?
The incidence of seizures in later stages is around 11 to 16 %. The prognosis for benign familial neonatal convulsions is good, and the condition resolves with no neurologic sequelae.
Patient Education:
The individuals affected with benign familial neonatal convulsions are counseled and educated about the risks to the family members. Reassurance is given to individuals as it is a benign condition. However, families need to be alerted about the dangers of developing epilepsy. The risks of developing minor neurologic problems are the same as the general population.
What Are the Clinical Signs and Symptoms of Benign Familial Neonatal Convulsions?
Individuals with benign familial neonatal convulsions are checked for other causative elements for neonatal seizures, such as perinatal or prenatal stroke, fever, perinatal asphyxia, persistent lethargy, pertinent maternal illness, drug abuse, neurologic abnormalities, or signs of metabolic dysfunction.
Suggested diagnostic criteria given by miles and homes involve:
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Normal neurologic evaluation findings.
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Absence of alternate etiologic findings.
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Normal intellectual and developmental outcomes are retrospective criteria.
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Positive family history of infantile or newborn criteria.
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Early onset of seizures in the neonatal period or infancy.
Physical Examination Findings:
The findings are normal during the interictal period, and neurologic findings also do not show any abnormalities.
Diagnostic Considerations:
Individuals with benign familial neonatal convulsions are checked for other causative elements for neonatal seizures and a diagnosis for meningoencephalitis or intracranial hemorrhage, which is treatable during early stages. However, these conditions may only present as seizures in the early stages of life. Also, child abuse should be suspected in neonates post-delivery. Other considerations involve vitamin B6 deficiency, arteriovenous malformations, maternal drug abuse, and tuberous sclerosis.
What Is the Differential Diagnosis for Benign Familial Neonatal Convulsions?
The differential diagnosis includes:
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Viral encephalitis.
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Pediatric febrile seizures.
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Focal (partial) epilepsy.
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Neonatal seizures.
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Neonatal injuries in child abuse.
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Intellectual disability.
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Infantile spasm (west syndrome).
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Frontal lobe epilepsy.
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Aseptic meningitis.
What Are the Investigations for Benign Familial Neonatal Convulsions?
Investigations include:
Laboratory Tests:
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Chemistry tests to obtain a basic metabolic panel for calcium, phosphorus, and magnesium levels, thyroid function tests, and check for vitamin B levels.
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Basic blood tests to check for complete blood count activated partial thromboplastin time and prothrombin time.
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Lumbar puncture checks for cerebrospinal fluid to rule out occult blood or neonatal meningoencephalitis.
Other investigations include computed tomography, electroencephalography, and magnetic resonance imaging (MRI) of the brain to rule out intracranial hemorrhage or structural lesions.
What Is the Treatment for Benign Familial Neonatal Convulsions?
Antiepileptic medications help in reducing or preventing the occurrence of status epilepticus. During the antiepileptic treatment, the seizures may subside, but the electroencephalography may show abnormalities. Antiepileptic medications do not alter the potassium channels, whereas other drugs may affect the potassium transporter. Medications are selected based on the following:
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Appropriateness of the drug on infants.
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Lack of serious side effects.
The condition is benign, so it becomes an important factor in selecting medicines. The drugs used are generally Phenobarbital, Benzodiazepines, Fosphenytoin, and Levetiracetam.
Conclusion
Benign familial neonatal convulsion is a condition that causes recurrent seizures in a newborn child. Gene mutations usually cause it. Treatment is mostly a medical approach. Families of the affected child are advised to undergo genetic counseling and medical screening due to the risk of developing epilepsy.
