Infantile Spasms Syndrome (West Syndrome)

Infantile spasms are a specific type of seizure that begin in the first one to two years of life. Infantile spasms can be associated with a developmental regression (a loss of developmental milestones) and a highly irregular pattern of brain electrical activity, called hypsarrhythmia. When all three features — spasms, developmental regression and hypsarrhythmia — are seen together, this is referred to as infantile spasms syndrome. Previously, infantile spasms syndrome was also called West syndrome.

Infantile spasms syndrome is considered an epileptic encephalopathy, conditions in which children have both seizures and cognitive and developmental impairments. Spasms and hypsarrhythmia can directly contribute to cognitive and behavioral impairments.

Infantile spasms need to be treated as quickly as possible.

Infantile spasms typically start between the ages of 4 months and 8 months. During the typical seizures, called spasms, the child’s body may suddenly bend forward, and the arms and legs may stiffen. Some children arch their backs while extending their arms and legs.

Spasms most commonly occur during transitions between waking and sleeping and after feeding. They last one to two seconds each but may occur in clusters of many spasms at a time, and children can have dozens of these spasm clusters in a day.

Infantile spasms syndrome can be caused by a number of conditions. Sometimes infantile spasms are caused by an injury to the brain. Other times, they are caused by developmental anomalies of brain structure. Infantile spasms can also be caused by genetic mutations or metabolic disorders.

Many genes have been identified that are associated with infantile spasms syndrome. In almost all cases when infantile spasms syndrome is found to be caused by a genetic mutation, it has occurred spontaneously (de novo) and was not inherited from either parent.

Mutations in least 100 individual genes have been identified so far that cause infantile spasms syndrome. Some of these genes include CDKL5, SCN2A, SCN8A and STXBP1. Tuberous sclerosis, which is caused by pathogenic variants in the genes TSC1 and TSC2, can also lead to infantile spasms syndrome.

In about 5% of children with infantile spasms syndrome, larger pieces of DNA that affect multiple genes are missing or extra (microdeletions or microduplications).

In some cases, no cause can be found.

At Children’s Hospital of Philadelphia’s Neuroscience Center, a child’s care begins with a comprehensive, personalized assessment of their medical history, a physical examination and diagnostic tests.

The observation of movements concerning for infantile spasms typically leads to an urgent EEG test to measure the electrical activity in the brain and look for the irregular brain waves of hypsarrhythmia. Several EEGs, done at different times in the child’s awake/sleep cycle, may be needed to detect hypsarrhythmia. Sometimes a prolonged EEG for several hours (up to 24 hours) may be used to capture the spasms themselves on EEG. Especially in the early stage of the condition, soon after the onset of spasms, the EEG may appear normal when the child is awake and only show irregularity when the child is asleep.

Additional tests and imaging may be done to find the underlying cause of the condition in order to inform the treatment plan, including:

Neuroimaging to look for abnormalities in the brain’s structure or evidence of prior brain injury.
Blood tests to detect the presence of a metabolic condition.
Genetic testing, including epilepsy panel testing or whole exome sequencing, to look for specific genetic causes of infantile spasms syndrome. Genetic testing is able to identify a positive genetic diagnosis in up to 40% of children with infantile spasms syndrome.

Identifying a genetic cause can provide families with an explanation for why their child has developed infantile spasms, may inform prognosis, can guide treatment choices, and can provide information regarding recurrence risks for future siblings or other family members.

The primary goal of treatment for infantile spasms syndrome is to eliminate the spasms and resolve the hypsarrhythmia pattern on EEG, if present. Early and effective treatment of spasms may improve the child’s long-term outlook.

Treatments for infantile spasms syndrome may include:

Medications: Seizures may be controlled with medications such as corticosteroids and the anti-seizure medication vigabatrin.
Surgery: If the seizures are found to be the result of a brain lesion, surgical removal of the lesion may bring improvement.
Metabolic treatment: If the seizures are found to be caused by an underlying metabolic condition, treating the cause of the metabolic problem can help to reduce the seizures.
Ketogenic diet: For children who are having problems with medications, or whose seizures are not being well controlled, the ketogenic diet may be helpful. This type of diet is low in carbohydrates and high in protein and fat.

After a comprehensive evaluation and careful diagnosis, we work closely with families to develop a personalized seizure management plan. Family training and support is a key element in a successful treatment plan. Parents and caregivers must know how to watch for and respond to seizures.

If the child experiences developmental delays or regression, physical therapy, occupational therapy and speech therapy may be helpful.

The long-term outlook for children with infantile spasms syndrome depends on the underlying cause of the condition and the extent to which it results in cognitive impairments.

Children who have typical development before the onset of spasms, receive effective treatment to control the spasms soon after their first appearance, and have no underlying brain abnormalities or genetic mutations may do well.

In a child with infantile spasms syndrome, the spasms usually stop by age 5, but they may be replaced by other types of seizures.

The Epilepsy Neurogenetics Initiative (ENGIN) at Children’s Hospital of Philadelphia's Neuroscience Center integrates the diagnosis and treatment of children with difficult-to-treat or unexplained epilepsies, genetic epilepsy syndromes and other genetic neurodevelopmental disorders. We combine cutting-edge clinical care and advanced genetic testing with innovative research to identify the underlying cause of a child’s epilepsy and develop an individualized approach to treatment and management.

We provide:

Expedited evaluation for children with suspected infantile spasms
Comprehensive diagnostic testing for patients with infantile spasms including electroencephalography, neuroimaging, metabolic testing and genetic testing
Access to the most effective treatments for infantile spasms including medications, the ketogenic diet and epilepsy surgery

Children’s Hospital of Philadelphia’s Pediatric Epilepsy Program and Epilepsy Neurogenetics Initiative accept referrals from primary care providers and specialists from across the U.S. and internationally.

If you are a pediatrician and are concerned that your patient has new onset infantile spasms, please contact our physician referral line to request an expedited evaluation: 1-800-879-2467 (1-800-TRY-CHOP).
If you are a pediatrician or neurologist and want to refer your patient to CHOP for additional diagnostic evaluation or treatment of infantile spasms syndrome, please contact the Epilepsy Neurogenetics Initiative (see below) for an appointment with one of our epilepsy specialists.