Infantile epileptic spasms syndrome is a rare seizure disorder that affects babies and young children and often leads to developmental challenges. Early diagnosis and treatment are crucial for improving outcomes. Although the condition can cause significant long-term problems, prompt treatment may help control seizures and support development. Families and caregivers play an important role in recognizing symptoms and working with the care team.

Infantile epileptic spasms syndrome is a seizure disorder that occurs in infancy or early childhood. It causes sudden muscle spasms and often leads children to stop gaining new skills or lose skills they had already learned. The condition was previously called West syndrome, named after William West, who first described it.

It includes three features: epileptic spasms, stopping or losing developmental progress, and a specific pattern of chaotic electrical activity in the brain called hypsarrhythmia. This pattern is detected with an electroencephalogram, or EEG. Children can have infantile epileptic spasms syndrome without having all three features.

Most children with infantile epileptic spasms syndrome develop symptoms between 3 and 12 months of age, but symptoms can begin between 1 month and 2 years of age. The spasms may involve the neck, trunk, arms, or legs. They can cause bending, straightening, or a combination of both. Spasms often occur in clusters, especially after waking, and may be subtle or mistaken for normal movements.

Infantile epileptic spasms syndrome accounts for about 2% of childhood epilepsy cases but up to 25% of epilepsy cases that begin in the first year of life.

Many different factors can cause infantile epileptic spasms syndrome. These factors may affect the brain before, during, or after birth.

Common causes include:

• Structural brain malformations: Abnormal brain development can disrupt normal brain function.
• Brain injury: Lack of oxygen, trauma, or infections may damage the brain and lead to spasms.
• Genetic changes and conditions: Changes in certain genes and genetic conditions, including tuberous sclerosis complex and Down syndrome, can cause spasms.
• Metabolic disorders: Problems with how the body processes chemicals may affect brain function.
• Congenital infections: Infections acquired before birth, such as cytomegalovirus (CMV), can damage the developing brain.
• Unknown causes: In some children, no cause is found. These cases are called cryptogenic.

Symptoms of infantile epileptic spasms syndrome include seizures characterized by sudden muscle contractions and changes in development. Symptoms can range from subtle to pronounced and often occur in clusters. Symptoms may include:

• Epileptic spasms: Brief contractions or extension of the neck, trunk, arms, or legs that last a few seconds. They usually occur in clusters, with interval between spasms of several seconds. Each cluster may last several minutes.
• Epileptic spasms: These spasms can be subtle, characterized only by head nodding, eye rolling, or brief stiffening that may be mistaken for normal behavior.
• Crying during or after spasms: Some infants may cry or appear distressed.
• Loss of skills: A child may lose skills already learned, such as sitting, rolling over, or babbling.
• Decreased social interaction: Less interest in surroundings or less interaction with others.

Doctors diagnose infantile epileptic spasms syndrome based on the child’s symptoms and the results of specialized tests.

The doctor will review the child’s medical history, including details about the spasms, developmental progress, and any previous brain injury. The doctor will also perform a physical and neurological examination to check for signs of developmental delay or other abnormalities.

Medical tests used to diagnose infantile epileptic spasms syndrome include:

• EEG: Records electrical activity in the brain and checks for abnormal patterns, including hypsarrhythmia.
• Video-EEG monitoring: Records brain activity and video, often overnight, to capture spasms and confirm the diagnosis.
• Magnetic resonance imaging (MRI): Provides detailed images of the brain to identify structural abnormalities or damaged areas.
• Blood and urine tests: Check for infections or problems with how the body processes certain chemicals that may cause spasms.
• Genetic testing: Identifies genetic changes or syndromes linked to the condition.
• Lumbar puncture, or spinal tap: May be performed if an infection or metabolic disorder is suspected.

Treatment for infantile epileptic spasms syndrome aims to stop the spasms, resolve abnormal brain activity, and support development. Treatment should begin promptly after diagnosis.

Treatment options include:

• Hormonal therapy: Adrenocorticotropic hormone (ACTH) or oral steroids such as prednisone or prednisolone are often used first. ACTH is given by injection, while oral steroids are taken by mouth. Both can help control spasms and resolve abnormal EEG patterns.
• Vigabatrin: This antiseizure medicine increases the level of a brain chemical that reduces nerve activity. Vigabatrin is especially effective for children with tuberous sclerosis complex and may be used in other cases.
• Ketogenic diet: This high-fat, low-carbohydrate diet may help control spasms in children who do not respond to medicines or who have certain metabolic disorders.
• Pyridoxine, or vitamin B6: This treatment is used for infants with a rare type disorder called pyridoxine (vitamin B6) dependency.
• Other antiseizure medicines: Medicines such as valproate, topiramate, zonisamide, or benzodiazepines may be tried if first-line treatments do not work, but they are generally less effective.
• Surgery: Surgery may be considered for children whose spasms do not respond to medicines and who have a damaged or abnormal area in one part of the brain that can be removed.

Complications of infantile epileptic spasms syndrome can affect many areas of development and health. The main complications include:

• Persistent epilepsy: Many children develop other types of seizures, including Lennox-Gastaut syndrome or other seizure types.
• Developmental delay: Problems with movement, thinking, speech, and social skills are common.
• Intellectual disability: Moderate to severe learning difficulties may occur.
• Autism: Some children develop autism or autistic traits.
• Behavioral issues: Hyperactivity, irritability, or sleep problems may develop.

The outlook for people with infantile epileptic spasms syndrome depends on the underlying cause, the timing of diagnosis, and the response to treatment. Unfortunately, many children experience developmental challenges and drug-resistant epilepsy. Children with cryptogenic forms, in which no clear cause is found, tend to have a better prognosis than those with symptomatic forms caused by a known brain injury or disorder.

Early recognition and prompt treatment improve the chances of better developmental and seizure outcomes. However, many children develop other seizure types or moderate to severe developmental disabilities. The condition can be life-threatening, particularly in children with serious health problems affecting the respiratory system.

This article was medically reviewed in August 2026.