clinical features of infantile spasms

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The most typical manifestations are the spasms.

  • spasms present as brief symmetrical contractions of musculature of the neck, trunk and extremities lasting up to several seconds
  • they occur in clusters which may vary from a few to more than a hundred per cluster
    • a cluster can be from less than a minute to more than 10 minutes in duration
  • they may vary from subtle, single, spasms such as a head nod or tonic eye rolling, to full body flexor, extensor or mixed spasms occurring in clusters many times throughout the day (1)
  • in majority of events, there is an initial phasic component lasting less than 1 to 2 seconds, followed by a less intense but generally more sustained tonic contraction, which could last up to about 10 seconds.
    • the tonic phase may be absent and only the initial phasic component is present in some infants
  • spasms may vary according to several factors
    • the muscle groups involved - flexor, extensor or mixed
      • mixed spasms - in 50% of cases
      • flexor spasms - in 42% of the cases
    • the intensity of the contraction
    • position of the infant during the attack (supine or sitting)
  • tends to occur more often on awakening or when falling asleep 
  • irritability or crying is frequent during or after the spasms (1,2,3)

The observer may note the following sequence of events in a stereotypical infantile spasm:

  • with the body held rigid, both arms are held with the elbows extended and the shoulders abducted to 90 degrees
  • with the elbows still extended, the arms are bought into the midline
  • as the seizure ends the infant usually cries as they regain normal consciousness.

In the longer term there is often cognitive impairment and cerebral palsy.


Last reviewed 05/2021