Infantile Spasms

Clinical Background

Infantile spasms are a type of seizure seen in an epilepsy syndrome of infancy and childhood known as West syndrome. The onset of infantile spasms is usually in the first year of life, typically between ages 3 and 7 months. Spasms often occur in a series, separated by intervals of 5-30 seconds, and may last for more than 10 minutes. Electroencephalogram (EEG) patterns of the spasms consist of a high-amplitude and diphasic slow wave. The interictal EEG pattern is described as hypsarrhythmic, as it is characterized by asynchronous and high-amplitude slow waves and multifocal spikes. Both fast and slow variants, depending on the aetiology, have been reported. Infantile spasms usually stop by five years of age, but may be replaced by other seizure types.1

Many underlying disorders, such as birth injury, metabolic disorders and genetic disorders, can give rise to spasms, making it important to identify them (symptomatic IS). Cerebral anomalies are detected in 70%-80% of cases. In some children, no cause can be found (cryptogenic IS). Due to ongoing seizure activity, there is a high risk of developmental delays and cognitive problems.1

Early control of seizures is critical for reducing developmental delays and cognitive problems; about 5% of infants with this condition eventually die from complications caused by the seizures. The incidence of infantile spasm is 1 per 2000 to 4000 live births. Boys are more prone to have IS and account for about 60% of the cases. Approximately 10,000-20,000 infants are afflicted worldwide.1

Learn more about the Infantile Spasm clinical development program.


  1. Orphanet. West syndrome. Updated March 2007. Acessed December 14, 2017.

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