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Etiology and pathogenesis of infantile spasms

Daniel G Glaze, MD
Section Editor
Douglas R Nordli, Jr, MD
Deputy Editor
Janet L Wilterdink, MD


Infantile spasms (IS) is an age-specific epileptic disorder of infancy and early childhood. Children with IS typically exhibit epileptic spasms along with the electroencephalographic pattern known as hypsarrhythmia. The triad of spasms, arrest of psychomotor development, and hypsarrhythmia is known as West syndrome.

IS as used in this topic is not considered to be interchangeable with the term "epileptic spasms." Epileptic spasms refers not only to the seizures seen in IS but also late-onset spasms and periodic spasms.

While relatively rare, IS is a significant disorder because of the strong association with developmental delay or regression (75 to 93 percent of affected children), high mortality rate, refractoriness to conventional antiseizure drugs, and responsiveness to hormonal therapy [1,2].

The epidemiology, etiology, pathogenesis, and pathology of IS are reviewed here. The clinical features and diagnosis, and management and prognosis are discussed separately. (See "Clinical features and diagnosis of infantile spasms" and "Management and prognosis of infantile spasms".)


Infantile spasms (IS) is a rare disorder with an incidence of 1.6 to 4.5 per 10,000 live births [3-6]. In a cross-sectional, population-based surveillance system that included 21 EEG laboratories in Atlanta, Georgia, the incidence was 2.9 per 10,000 live births among children born in 1975 to 1977 [3]. The prevalence among 10-year-old children was 2.0 per 10,000; the lower prevalence than incidence likely reflecting the substantial mortality of the disorder [3,6]. However, a history of IS was found in a substantial proportion, 12 percent, of children with profound mental retardation.

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Literature review current through: Nov 2017. | This topic last updated: Oct 06, 2017.
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