West Syndrome

What is West syndrome?

West syndrome is defined by the presence of three features:

  • Infantile spasms, a specific type of seizures that begin in the first year of life
  • Developmental regression or a loss of developmental milestones
  • A highly irregular pattern of brain waves, known as hypsarrhythmia, on an electroencephalogram (EEG)

A child must have all three of these features to be diagnosed with West syndrome.

Infantile spasms in West syndrome typically start between the ages of 4 months and 8 months. During the seizures, which last for one to two seconds each, the child’s body may suddenly bend forward and the arms and legs stiffen. Some children arch their backs while extending their arms and legs. The spasms most commonly occur during transitions between waking and sleeping and after feeding. They may occur in clusters of many spasms at a time, and affected children can have dozens of these spasm clusters in a day.

Causes of West syndrome

West syndrome can be caused by a number of conditions. Sometimes West syndrome is caused by an injury to the brain. Other times, it is caused by developmental anomalies of brain structure. West syndrome can also be caused by genetic mutations or metabolic disorders.

In some cases, no cause can be found.

Diagnosis of West syndrome

The observation of infantile spasms typically leads to an EEG test to look for the irregular brain waves of hypsarrhythmia to confirm the diagnosis. 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 or in REM sleep, and only show irregularity in light sleep or right after waking up.

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

  • Neuroimaging may be used to look for lesions or other structural brain abnormalities.
  • Blood tests may be done to detect the presence of a metabolic condition.
  • Genetic testing may be done to look for specific genetic causes of West syndrome.

Genetics of West syndrome

Many genes have been identified that are associated with West syndrome, and in almost all cases when West syndrome is found to be caused by 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 West 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 West syndrome.

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

Genetic testing, including epilepsy panel testing or whole exome sequencing, is able to identify a positive genetic diagnosis in up to 40% of children with West 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 recurrences risks for future siblings or other family members.

West syndrome treatment

The primary goal of treatment for West syndrome is to eliminate the seizures and resolve the hypsarrhythmia pattern on EEG, if present. West syndrome is considered an epileptic encephalopathy, a condition in which the epileptic seizures can directly contribute to cognitive and behavioral impairments. Early and effective control of the seizures can improve the child’s long-term outlook.

  • Seizures may be controlled with medications such as corticosteroids and the anti-seizure drug vigabatrin.
  • If the seizures are found to be the result of a brain lesion, surgical removal of the lesion may bring improvement.
  • 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. A ketogenic diet may be helpful in some cases.

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.

Long-term outlook for children with West syndrome

The long-term outlook for children with West 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 may do well.

The infantile spasms of West syndrome usually stop by age 5, but they may be replaced by other types of seizures.

Why choose CHOP for care of a child with West syndrome?

The Epilepsy Neurogenetics Initiative (ENGIN) at Children’s Hospital of Philadelphia integrates genetic testing into 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.

Families come to our ENGIN clinic from all over the world. Through ENGIN, your child will have access to any other medical specialists they may need, as well as a full range of epilepsy therapies provided through CHOP’s Pediatric Epilepsy Program, including medication, dietary treatment and epilepsy surgery, as well as ongoing follow-up care.

Resources and additional information about West syndrome

Epilepsy Foundation


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