• Consists of a sudden jerk followed by stiffening.
  • Each seizure lasts only a second or two but usually in a series.
  • Most common just after waking up and rarely occur during sleep.
  • They typically begin between 3 and 12 months of age and usually stop by 4 years old.
  • Steroid therapy and the antiseizure medicine Sabril are the primary treatments.
  • Most children are developmentally delayed later in life.
  • Many children develop other kinds of epilepsy.

Infantile spasms (also called IS) are also known as West syndrome because it was first described by Dr. William James West, in the 1840s. The spasms consist of a sudden jerk followed by stiffening. Often the arms are flung out as the knees are pulled up and the body bends forward ("jackknife seizures"). Less often, the head can be thrown back as the body and legs stiffen in a straight-out position. Movements can also be more subtle and limited to the neck or other body parts. Each seizure lasts only a second or two but they usually occur close together in a series. Sometimes the spasms are mistaken for colic, but the cramps of colic do not occur in a series.

Infantile spasms are most common just after waking up and rarely occur during sleep.

Who gets it?

Infantile spasms begin between 3 and 12 months of age and usually stop by the age of 2 to 4 years. They are uncommon, affecting only one baby out of a few thousand. About 60% of the affected infants have some brain disorder or brain injury before the seizures begin, but the others have had no apparent injury and have been developing normally. There is no evidence that family history, the baby's sex, or factors such as immunizations are related to infantile spasms.

Tell me more

When a baby with infantile spasms has an EEG, the doctor usually will see an unusual pattern called hypsarrhythmia (HIP-sa-RITH-me-ah) when the seizures are not occurring. This chaotic, high-voltage pattern is often helpful in confirming the diagnosis.

Babies with infantile spasms seem to stop developing and may lose skills that they had already mastered, such as sitting, rolling over, or babbling.

How is it treated?

  • The primary approved treatments for children with infantile spasms include: 
    • Steroid therapy (adrenocorticotropic hormone [ACTH by injection] or prednisone)
    • A seizure medication called Sabril (vigabatrin)
  • Some pediatric seizure doctors prefer therapy with Sabril (vigabatrin) or other seizure medications that may appear helpful for IS, for example Depakote (valproate) or Topamax (topiramate) before steroid therapy. 
  • Sabril is especially effective for children with tuberous sclerosis (a disorder associated with abnormalities involving the brain, skin, heart, and other parts of the body).
  • Sabril is associated with damage to the retina of the eye and should be used with caution in children. The retinal damage can result in permanent loss of peripheral vision, but this side effect is of more concern when the drug is used for many months. Monitoring of vision is important.

What's the outlook?

  • Most children with infantile spasms are developmentally delayed later in life.
  • Those whose spasms are related to an underlying developmental brain disorder or injury have a higher likelihood of moderate to severe delay.
  • The outlook is brighter for those who were developing normally before the spasms started: 10 to 20% will have normal mental function and some others may be only mildly impaired.
  • Some children with infantile spasms develop autism.
  • Many doctors believe that the quicker the seizures are controlled, the better the results will be.
  • When the spasms stop, many children later develop other kinds of epilepsy. About one-fifth of children who have had infantile spasms will have the Lennox-Gastaut syndrome.
Authored by: Gregory L. Holmes, MD | Robert S. Fisher, MD, PhD on 9/2013
Reviewed by: Robert S. Fisher, MD, PhD on 9/2013
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What It Looks Like...

Here's a typical story: "At first I thought Chris was just having the little body jerks when he was moved or startled, like my other children had when they were infants. But then I knew something was wrong. The jerks became more violent, and his tiny body was thrust forward and his arms flew apart. They only lasted a few seconds but started to occur in groups lasting a few minutes. It was so hard to see such a young baby having these things."

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