What are Infantile Spasms (West Syndrome)?

Reviewed by: HU Medical Review Board | Last reviewed: March 2022

Infantile spasms are a type of seizure in babies. The seizures typically happen in the morning and can cause crying and stiffening of the body.1,2

Infantile spasms are also known as West syndrome. This is because the condition was first discovered by Dr. William James West.1

Infantile spasms may be a sign of an underlying medical condition. Some conditions linked to infantile spasms include:1,2

  • Epilepsy
  • Intellectual disability
  • Autism

What do infantile spasms look like?

Infantile spasms typically happen in the morning and may occur up to 100 times a day. The most common symptom of infantile spasms is a sudden jerk or twitch of the body. This may be accompanied by:1,2

Infantile spasms can be called "jackknife seizures" or "flexor spasms" because of how the seizures appear. Your baby's body can fold forward like a pocketknife. Their knees will pull up, and their arms will flail to the sides.1,2

Other symptoms include:1

  • Sudden stiffening of the muscles
  • Head thrusting back as legs stiffen in a straight position

Sometimes infantile spasms symptoms are subtle and hard to notice. The spasms can be mistaken for colic. However, pain from colic does not occur in a series the way infantile spasm seizures do.1

What causes infantile spasms?

In about 2 out of 3 babies, infantile spasms have a known cause. Some of these causes include:1

  • Genetic disorders, like tuberous sclerosis
  • Infections, like meningitis or encephalitis
  • Brain injuries
  • Metabolic disorders, like maple syrup urine disease
  • Structural defects in the brain

Diagnosing West syndrome

The doctor will perform a physical exam and ask about your child's symptoms. They will perform a brain and nerve (neurological) exam. The exam includes:1,2

  • Questions about your child's seizures, including what they look like and how often they occur.
  • A history of your child’s development and any prior brain injury.
  • An EEG (electroencephalogram) to look at the electrical activity of the brain.

Most babies diagnosed with infantile spasms/West syndrome will also need other tests, for example:1,2

  • MRI (magnetic resonance imaging) scan of the brain
  • Blood test
  • Urine test

Treating infantile spasms

It is important to treat infantile spasms as quickly as possible with the most effective therapies. Treatments include:1-3

Adrenocorticotropic hormone (ACTH)

Adrenocorticotropic hormone (ACTH) is made naturally in the body. ACTH works to release other hormones in the body. Daily injections of ACTH started soon after diagnosis have been shown to improve outcomes in infantile spasms. Doctors are not sure the exact reason why ACTH helps with infantile spasms.3

Injections of ACTH are started in the hospital, usually at an epilepsy treatment center. Your child’s doctor or nurse will teach you how to give these injections at home.3


Steroids are potent anti-inflammatory drugs. The steroids prednisone or prednisolone can be prescribed for infantile spasms.1,2

Anti-seizure drugs

For infantile spasms, vigabatrin is the specific drug usually prescribed. Depending on your child’s condition and symptoms, other anti-seizure drugs may be used. However, infantile spasms do not usually respond well to other anti-seizure drugs.1,2

Change in diet

Some babies with infantile spasms have seizures that can be decreased by a ketogenic (keto) diet. A keto diet is a diet where you eat a lot of fat and not many carbohydrates. This forces your body to use fat for energy instead of glucose. It is a tough diet to follow, but it can be worth it if your baby's doctor thinks it might help.1,2

The keto diet has known and unknown side effects. People who follow it should be closely monitored by their doctors. The keto diet effectively treats seizures for some people. Doctors are still uncertain about why it works for some people but not others.1,2

Treating seizures early is essential to improved outcomes. Many children end up with intellectual problems, but outcomes vary greatly from child to child. Talk to your child’s doctor about your child’s symptoms and treatment options.

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