Infantile spasms (IS), also known as West syndrome, are a rare form of epilepsy that typically occur in babies under the age of 1 year.

Babies with the condition will often experience clusters of short seizures. It is a severe form of epilepsy because medical professionals often associate it with developmental delays.

The long-term outlook for children with IS varies greatly. Many experience developmental delays, but about 20% of children move through the typical developmental stages without any concerns, according to the Child Neurology Foundation.

This article reviews what infantile spasms are in more detail, including their symptoms, causes, diagnosis, treatment, and more.

A baby with infantile spasms.Share on Pinterest
Jessica Rinaldi/The Boston Globe via Getty Images

IS is a rare, severe form of epilepsy. Researchers and medical professionals associate IS with developmental delays and an overall poor prognosis.

William James West first identified infantile spasms in 1841, so medical professionals sometimes refer to them as West syndrome. Other names can include epileptic spasms and infantile spasms syndrome.

Early treatment can help prevent more severe complications. A 2018 journal article estimated that 25% of infants with IS — those who receive a prompt diagnosis and early, successful treatment — achieve a seizure-free life and have a better intellectual outcome.

However, they estimate that the remainder will face higher risks of intellectual disability and continued seizures.


The Epilepsy Foundation encourages parents and caregivers to use the acronym STOP to ensure infants receive prompt diagnosis and treatment.

The mnemonic is as follows:

  1. See the signs: Look for clusters of sudden, uncontrollable, repetitive movements such as body stiffening and head bobbing.
  2. Take a video: Record the symptoms to show to a medical professional.
  3. Obtain a diagnosis: Take the infant for an EEG test to look for irregular brain wave patterns.
  4. Prioritize treatment: Receiving early treatments can improve the child’s outlook.

At first, parents or caregivers may mistake IS for other movements, such as those associated with colic, sleep jerks, or reflux.

Infantile spasms appear as quick body jerks that typically do not last long, but they may occur in clusters.

The symptoms will typically start between ages 4–8 months.

When a baby spasms, they may:

  • suddenly bend at the waist
  • stick their arms straight out to the side
  • roll their eyes back suddenly with subtle head nodding
  • raise their arms over their head
  • stiffen their legs or bend them toward the stomach as if in abdominal pain
  • drop or bob their heads briefly
  • lose balance while sitting

In addition to jerky motions, a baby with IS may:

  • be inconsolable
  • smile less
  • appear unhappy
  • seem irritable
  • are less interactive and engaged in their environment

A child may also have hypsarrhythmia, though not all children with IS will experience this. Hypsarrhythmia is abnormal brain wave activity that a doctor can see on an electroencephalogram (EEG) test.

Many different underlying conditions may cause infantile spasms. Some possible causes include:

Some additional common causes include:

  • hypoxic-ischemic encephalopathy
  • CDKL5 deficiency disorder
  • tuberous sclerosis complex
  • Aicardi syndrome
  • brain abnormalities, such as focal cortical dysplasia, polymicrogyria, hemimegalencephaly, and lissencephaly
  • duplication 15q syndrome (Dup15q)

However, in some cases, a doctor cannot identify a cause.

Researchers have not found any evidence to associate a person’s family history or sex with infantile spasms. They also have not found any link between vaccines and infantile spasms.

Infantile spasms are a severe, rare form of epilepsy.

Other epilepsy syndromes include:

A child with infantile spasms may go on to develop other forms of epilepsy later in life.

Early diagnosis can help improve a child’s overall outlook.

A parent or caregiver should talk with a doctor about their concerns. If a doctor suspects IS, they will likely refer the child to a neurologist.

A neurologist will likely perform a physical examination and ask about the symptoms and signs a baby is showing. They will also likely review the family and medical history of the baby.

An EGG can help determine if a child has hypsarrhythmia, which can help with diagnosis. However, not all children with IS will have abnormal brain wave activity.

They may also order an MRI scan to get a picture of the brain. Sometimes, doctors can order genetic testing to look for changes in the infant’s DNA that may explain the origin of the spasms.

Treatment goals are twofold. A doctor will want to stop:

  • future seizures from occurring
  • hypsarrhythmia

There are two main types of therapies doctors may suggest. They include:

  • Hormone therapy: This includes adrenocorticotropic hormone (ACTH) or prednisolone, though dosing and regiments may vary between facilities and hospitals.
  • Vigabatrin: An anti-seizure medication that has moderate success rates. However, there is a risk of severe side effects, such as loss of vision and brain toxicity.

About 40–80% of children will stop having seizures when using hormone therapy, according to the Child Neurology Foundation. About 30–40% of children who take vigabatrin will see their symptoms clear.

In either case, children who successfully undergo treatment have a 30% chance of a relapse.

The outlook for children with infantile spasms varies based on the underlying cause.

However, in most cases, the intellectual expectation in children with the condition is poor due to the spasms starting after neurological impairments occur.

Children who receive rapid treatment, have no identifiable cause, and move through the developmental stages as expected before the start of treatment may do better than others.

Though the condition often resolves in mid-childhood, children may go on to develop new seizure disorders and have a higher risk of developing autism.

Early treatment is associated with better overall outcomes.

Untreated or delayed treatment of infantile spasms can lead to potentially serious complications. They include cognitive and behavior issues as well as developmental delays.

Treatment can also lead to side effects and possible complications, such as brain toxicity and vision loss.

There are many potential causes of infantile spasms, but some cases occur due to unknown causes. This makes prevention relatively difficult.

Parents may be able to help prevent long-term consequences by learning the signs and symptoms of infantile spasms and seeking help if they notice their child exhibiting them.

A parent or guardian should note unusual movement patterns or development concerns and speak with a doctor if they notice any signs that a child is missing developmental milestones.

A doctor may be able to help identify possible causes and recommend specialists that may be able to identify the underlying cause of the symptoms.

Since infantile spasms are generally rare, a child is more likely to experience other, more benign conditions.

The following sections provide answers to frequently asked questions about infantile spasms.

Do babies grow out of infantile spasms?

With treatment, a baby may no longer experience spasms.

However, about 1/3 of all children who recover will eventually have a relapse, according to the Child Neurology Foundation. A child may also go on to develop additional seizure disorders.

Can a baby with infantile spasms live a normal life?

About 20–30% of all children born with infantile spasms who receive treatment go on to live a full life.

What age do infantile spasms start?

The symptoms and signs of infantile spasms typically occur between ages 4–8 months, though they can start later in childhood.

IS is a rare, severe form of epilepsy disorder. It is associated with young infants, but it can develop later.

Several different conditions can cause the condition. However, some cases have no clear cause. A child has the best chance of recovery when they receive early treatment.

When they receive prompt treatment, around 25% of children with IS will go on to successfully meet their developmental milestones.