Benign Familial Neonatal Infantile Seizures (BFNIS)

Reviewed by: HU Medical Review Board | Last updated: December 2022

Benign familial neonatal infantile seizures (BFNIS) is a seizure syndrome that affects the nervous system of babies. Understanding what BFNIS is and how it is managed can help to ease concerns you may have about how it will affect your baby.1,2

Who gets benign familial neonatal infantile seizures?

Benign familial neonatal infantile seizures are a type of seizure that can happen in babies. They usually start when the baby is between 1 month and 6 months old. BFNIS usually goes away on its own by the time the child is 2 years old. But some babies will keep having seizures after they turn 2.2

What causes BFNIS?

Doctors do not know what causes BFNIS, but they think it might be genetic. If you have a baby with BFNIS, there is a chance that other babies in your family could have it. Talk to your doctor if you have any questions or concerns about BFNIS.1,2

Genes and BFNIS

BFNIS is caused by changes, or mutations, in certain genes. It is unclear how exactly these genes contribute to BFNIS, but researchers believe they play a role in controlling electrical activity in the brain. Mutations in these genes likely disrupt this process and lead to uncontrolled seizure activity.1-3

Inheritance

BFNIS can occur by an autosomal dominant inheritance. This means that if 1 parent has the mutation, there is a 50 percent chance of their child inheriting the disorder. But in some cases, the disorder can occur without any family history. This is referred to as "de novo" mutation, which means the mutation occurred spontaneously in the child.1,2,4

BFNIS Symptoms

Most babies with BFNIS have seizures that last a few seconds to a few minutes. The seizures usually happen several times a day. Some babies only have 1 or 2 seizures a day, while others may have up to 100 seizures a day.1,2

During a BFNIS seizure, the baby's eyes may roll back, and their body may stiffen. They may also make jerking movements with their arms and legs. Some babies cry during a seizure, while others do not.1,2

After the seizure, the baby may be tired and sleep for a short time. They will usually be back to their normal self within an hour after the seizure ends.1,2

Diagnosing benign familial neonatal infantile seizures

Doctors can do tests to check for BFNIS. One test is called an electroencephalogram (EEG). EEGs record your brain waves. Children with BFNIS usually have a certain pattern on their EEG. Genetic testing can also be done. This test can show if you or your baby have changes in certain genes that are linked to BFNIS.1,2

Other tests like magnetic resonance imaging (MRI) and lumbar puncture (spinal tap) may be needed to distinguish BFNIS from other conditions.1,2

Treatment

Typically, treatment starts with anti-seizure medications. Depending on which mutation is causing the disorder, drugs that block sodium channels may be an option.2

Outlook

The outlook for infants with BFNIS is generally good. The seizures usually go away on their own within a few months to a couple of years. And the seizures do not usually cause any long-term problems. In some cases, BFNIS may be linked to a slightly higher risk of developing epilepsy later in life, but this is still rare.1,2

If your child has BFNIS, talk to your doctor about the best way to manage it and what you can expect in the future. With proper treatment, most children with BFNIS will go on to lead healthy lives.1,2

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