What Is West Syndrome?

West syndrome is a type of epilepsy that affects babies. It’s named after the doctor who discovered it. You might hear it called infantile spasms.

Who Gets West Syndrome?

This condition is rare. It affects fewer than six babies out 10,000. Most infants get it before they’re a year old. The peak age of onset is between 4 and 8 months. Six out of 10 babies who have West syndrome are boys.

What Happens in West Syndrome?

It causes seizures. They only last a few seconds, but they happen in bunches called clusters. There can be as many as 150 seizures in a cluster, and some babies can have up to 60 clusters a day.

Usually, West syndrome stops by the time a child is 4 years old. But most people who had it will have other kinds of epilepsy or seizure conditions as children and adults.

Babies with West syndrome usually have mental disabilities later in life, but up to 1 in 5 will have normal mental function or only mild mental problems. Some will have autism.

Different Types of West Syndrome

Doctors may talk about three different kinds of West syndrome. They are:

  • Symptomatic: When another condition caused the West syndrome and your baby’s doctor knows what it is
  • Cryptogenic: When your baby’s doctor suspects another condition caused it but doesn’t know what it is
  • Idiopathic: When your baby was developing normally physically and mentally before West syndrome, and the cause is something in your genes rather than another health condition


WebMD Medical Reference Reviewed by Brunilda Nazario, MD on November 27, 2017



National Organization for Rare Disorders: “West syndrome.”

Medscape: “Infantile Spasm (West Syndrome).”

National Institutes of Health, Genetic and Rare Disease Information Center: “West syndrome.”

Epilepsy Foundation: “Infantile Spasms,” “Infantile Spasms (West’s Syndrome) and Tuberous Sclerosis Complex,” “West Syndrome (Infantile Spasms).”

Epilepsia: “The underlying etiology of infantile spasms (West syndrome): Information from the United Kingdom Infantile Spasms Study (UKISS) on contemporary causes and their classification.”

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