Infantile Spasms

Infantile Spasms is a topic covered in the Select 5-Minute Pediatrics Topics.

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  • Infantile spasms (IS) are seizures commonly associated with West syndrome—a severe infantile epileptic encephalopathy often with poor developmental outcome.
    • IS are characterized by sudden flexion, extension, or mixed flexion-extension of the neck, trunk, arms, and/or legs.
    • IS can be subtle such as a mild contraction of the abdominal muscles or subtle movements of the head, shoulder, or eyes.
    • IS can occur singly, but the clustering (often on awakening) is a key diagnostic feature.
  • IS are commonly dismissed as “normal” movements or misdiagnosed as reflux/colic.
  • West syndrome is classically the triad of (1) IS, (2) developmental delay, and (3) hypsarrhythmia—a chaotic, high amplitude EEG background typically associated with multifocal spikes.


  • The onset occurs in the 1st year of life in >90%, typically 3–12 months of age (peak onset 4–8 months, mean 6 months).
  • Rarely occurs after 18 months of age


The incidence is 2–3.5/10,000 live births.


  • Unknown
  • In 70–80% of cases, a specific condition is associated with IS; however, this does not necessarily suggest a direct cause-and-effect relationship with IS.

Commonly Associated Conditions

  • Hypoxic-ischemic encephalopathy (HIE)
  • Chromosomal disorders such as trisomy 21
  • Brain malformation such as holoprosencephaly, malformations of cortical development (such as pachygyria or lissencephaly [including Miller-Dieker syndrome with deletion of 17p13.3], hemimegalencephaly, schizencephaly, heterotopia, and focal cortical dysplasia)
  • Stroke
  • Intraventricular/intraparenchymal hemorrhage
  • Periventricular leukomalacia
  • Tuberous sclerosis complex (TSC)
  • Other neurocutaneous conditions such as neurofibromatosis type 1 (NF1), incontinentia pigmenti achromians (Hypomelanosis of Ito)
  • Disorders of X-linked inheritance such as Aicardi syndrome (consider in girls with agenesis of the corpus callosum and chorioretinal lacunae)
  • Hydrocephalus of various causes
  • There is an expanding list of IS-associated genes: ARX, CDKL5, FOXG1, GRIN1, GIN2A, MAGI2, SPTAN1, MEF2C, SLC25A22, STXBP1, SCN1A, SCN2A, GABRB3, and ALG13.
  • Trauma (any but often nonaccidental)
  • Progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy syndrome
  • Infections: meningitis/encephalitis, TORCH
  • Inborn errors of metabolism such as Menkes disease, disorders of amino acid metabolism (such as phenylketonuria and maple syrup urine disease), pyruvate dehydrogenase complex deficiency, mitochondrial disorders (such as Leigh syndrome), pyridoxine-dependent seizures, glucose transporter protein type 1 (GLUT1) deficiency, and uncommonly, organic acidurias (such as methylmalonic aciduria)

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