Benign familial neonatal seizures

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Benign familial neonatal seizures (BFNS) is a condition characterized by recurrent seizures in newborn babies. The seizures begin around day 3 of life and usually go away within 1 to 4 months. The seizures can involve only one side of the brain (focal seizures) or both sides (generalized seizures). This condition is often associated with generalized tonic-clonic seizures (also known as grand mal seizures). This type of seizure involves both sides of the brain and affects the entire body, causing a combination of seizure types: tonic seizures, which are characterized by uncontrolled muscle stiffness and rigidity, and clonic seizures, which are characterized by uncontrolled jerking of the muscles. Seizure episodes in infants with BFNS typically begin with tonic stiffness and pauses in breathing (apnea) followed by clonic jerking.

A test called an electroencephalogram (EEG) is used to measure the electrical activity of the brain. Abnormalities on an EEG test, measured during no seizure activity, can indicate a risk for seizures. However, infants with BFNS usually have normal EEG readings. In some affected individuals, the EEG shows a specific abnormality called the theta pointu alternant pattern. By age 2, most affected individuals who had EEG abnormalities have a normal EEG reading.

Typically, seizures are the only symptom of BFNS, and most people with this condition develop normally. However, some affected individuals develop intellectual disability that becomes noticeable in early childhood. A small percentage of people with BFNS also have a condition called myokymia, which is an involuntary rippling movement of the muscles. In addition, in about 15 percent of people with BFNS, recurrent seizures (epilepsy) will come back later in life after the seizures associated with BFNS have gone away. The age that epilepsy begins is variable.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in two genes, KCNQ2 and KCNQ3, have been found to cause BFNS. Mutations in the KCNQ2 gene are a much more common cause of the condition than mutations in the KCNQ3 gene.

The KCNQ2 and KCNQ3 genes provide instructions for making proteins that interact to form potassium channels. Potassium channels, which transport positively charged atoms (ions) of potassium into and out of cells, play a key role in a cell's ability to generate and transmit electrical signals.

Channels made with the KCNQ2 and KCNQ3 proteins are active in nerve cells (neurons) in the brain, where they transport potassium ions out of cells. These channels transmit a particular type of electrical signal called the M-current, which prevents the neuron from continuing to send signals to other neurons. The M-current ensures that the neuron is not constantly active, or excitable.

Mutations in the KCNQ2 or KCNQ3 gene result in a reduced or altered M-current, which leads to excessive excitability of neurons. Seizures develop when neurons in the brain are abnormally excited. It is unclear why the seizures stop around the age of 4 months. It has been suggested that potassium channels formed from the KCNQ2 and KCNQ3 proteins play a major role in preventing excessive excitability of neurons in newborns, but other mechanisms develop during infancy.

About 70 percent of people with BFNS have a mutation in either the KCNQ2 or the KCNQ3 gene. Researchers are working to identify other gene mutations involved in this condition.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person inherits the mutation from one affected parent. A few cases result from new mutations in the KCNQ2 gene. These cases occur in people with no history of benign familial neonatal seizures in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Benign familial neonatal seizures occurs in approximately 1 in 100,000 newborns.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Focal EEG discharges with secondary generalization · Very frequent (99-80%)

Focal EEG discharges that secondarily spread to both hemispheres and can then be recorded over the entire scalp.

Focal clonic seizure · Very frequent (99-80%)

A focal clonic seizure is a type of focal motor seizure characterized by sustained rhythmic jerking, that is regularly repetitive.

Focal tonic seizure · Very frequent (99-80%)

A type of focal motor seizure characterized by sustained increase in muscle contraction, lasting a few seconds to minutes.

Focal-onset seizure · Very frequent (99-80%)

A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures.

Neonatal seizure · Very frequent (99-80%)

A seizure occurring within the neonatal period (28 days beyond the full term date).

Apnea · Frequent (79-30%)

Lack of breathing with no movement of the respiratory muscles and no exchange of air in the lungs. This term refers to a disposition to have recurrent episodes of apnea rather than to a single event.

Circumoral cyanosis · Frequent (79-30%)

Persistent blue color of the skin that surrounds the mouth.

Clonus · Frequent (79-30%)

A series of rhythmic and involuntary muscle contractions (at a frequency of about 5 to 7 Hz) that occur in response to an abruptly applied and sustained stretch.

Other findings in the same source

From: Orphanet

Additional reported features include Focal autonomic seizure (Frequent (79-30%)); Generalized tonic seizure (Frequent (79-30%)); Limb myoclonus (Frequent (79-30%)); Axial hypotonia (Occasional (29-5%)); Facial tics (Occasional (29-5%)); Gastroesophageal reflux (Occasional (29-5%)); Simple febrile seizure (Occasional (29-5%)); Increased theta frequency activity in EEG (Very rare (<4-1%)); Status epilepticus (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Benign familial neonatal seizures is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Benign familial neonatal seizures. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.