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What is an infantile spasm (IS)?

Dr. Jeanne Morrison, PhD
Family Practitioner

An infantile spasm (IS) is a specific type of seizure seen in an epilepsy syndrome of infancy and childhood, known as West syndrome. West syndrome is characterized by ISs, developmental regression, and a specific pattern on electroencephalography (EEG) testing, called hypsarrhythmia (chaotic brain waves). The onset of ISs is usually in the first year of life, typically between four to eight months. The seizures primarily consist of a sudden bending forward of the body with stiffening of the arms and legs; some children arch their backs as they extend their arms and legs. Spasms tend to occur upon awakening or after feeding and often occur in clusters of up to 100 spasms at a time. Infants may have dozens of clusters and several hundred spasms per day. ISs usually stop by age five but may be replaced by other seizure types. Many underlying disorders, such as birth injury, metabolic disorders, and genetic disorders, can give rise to spasms, making it important to identify the underlying cause. In some children, no cause can be found.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.