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Clinical features and diagnosis 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. Infantile spasms were described first by West in 1841 [1]. 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.

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


IS is characterized by epileptic spasms with onset in infancy or early childhood that are usually associated with the electroencephalographic (EEG) pattern of hypsarrhythmia, and also developmental regression [2].

Age of onset — The majority (90 percent) of affected children present at less than one year of age, with a range from one day to 4.5 years of age (figure 1) [2-4]. The peak incidence of onset (50 to 77 percent) is between three and seven months; onset after 18 months is rare. The true age of onset may be uncertain because IS may be initially mistaken for other conditions, such as hyperirritability, exaggerated startle responses, and/or colic [5]. (See 'Differential diagnosis' below.)

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Literature review current through: Nov 2017. | This topic last updated: Jul 24, 2016.
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