Cerebellar hypoplasia is the underdevelopment of the cerebellum. Symptoms can include seizures, developmental delays, and difficulties with movement.

Cerebellar hypoplasia is the underdevelopment of a part of your brain called the cerebellum. It’s a structure at the back of your brain that has many functions, such as:

  • coordinating voluntary movements
  • maintaining balance and posture
  • allowing you to learn complex movement patterns, such as throwing a ball
  • coordinating movements related to language

Cerebellar hypoplasia can range from mild underdevelopment to a complete lack of a cerebellum. It can occur at birth or develop early in childhood.

In this article, we cover everything you need to know about cerebellar hypoplasia, including symptoms, treatment options, and risk factors.

Symptoms of cerebellar hypoplasia vary between people, depending on the severity of the condition and the part of the cerebellum affected. It doesn’t always cause symptoms.

Infants and young children can develop:

Older children might have:

Cerebellar hypoplasia is a feature of many different congenital syndromes, such as Joubert syndrome, and the most severe form of congenital muscular dystrophy, called Walker-Warburg syndrome.

Cerebellar hypoplasia can develop due to:

  • genetic differences that cause dificulties with cerebellum development in the womb
  • rare inherited neurodegenerative or metabolic conditions, such as:

Genetics of cerebellar hypoplasia

Researchers are still examining which genes are linked to the development of cerebellar hypoplasia. In a 2022 study, researchers identified disease-causing mutations in 96 of 176 families with a history of cerebellar hypoplasia. The most common genes that were linked to cerebellar hypoplasia were:

  • ITPR1
  • KIF1A

Other mutations linked to cerebellar hypoplasia include the following:

  • A mutation in the CASKgene has been linked to underdevelopment of the pons and cerebellum and microcephaly, a smaller than typical head.
  • BICD2gene mutations have been linked to cerebellar hypoplasia and lissencephaly, which is the loss of folds in the outer part of your brain.
  • PRDM12 mutations are linked to fatal brainstem dysfunction with cerebral hypoplasia.

Some gene mutations linked to hypoplasia are passed through families.

Not much is known about nongenetic causes of cerebellar hypoplasia, but it’s been linked to the following maternal exposures:

Pets and animals

All animals with a backbone, from fish to elephants, have a cerebellum. Like humans, animals can have genetic problems that cause difficulties with brain development. In animals like cats and dogs, cerebellar hypoplasia can cause symptoms like:

  • jerky movements
  • tremors
  • incoordination
  • trouble walking
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Underdevelopment of the cerebellum can range from mild to complete absence of the cerebellum. Children with severe malformation might have:

  • serious movement difficulties
  • learning and development delays
  • trouble or inability to walk
  • difficulties communicating

Cerebellar hypoplasia may also be a contributing factor in the development of autism spectrum disorder in some children.

Cerebellar hypoplasia can occur by itself or with other brain malformations. For example, it’s a component of Dandy-Walker malformation, which is characterized by:

  • enlargement of the fourth ventricle, a cavity in your brain
  • underdevelopment of a part of the cerebellum called the cerebellar vermis
  • enlargement of the base of the skull

Dandy-Walker malformation is linked to a risk of developing hydrocephalus, a serious condition in which cerebral spinal fluid builds up in the ventricles in the brain.

It’s important to contact a doctor if your child has developmental delays, seizures, and any other symptoms that could indicate a neurological condition.

Imaging plays a critical role in diagnosing cerebellar hypoplasia. It can be diagnosed before or after birth. MRI is the main type of imaging to diagnose cerebellar hypoplasia.

Electroencephalography can measure your child’s brain activity if they develop seizures to help identify the underlying cause.

A doctor may order a genetic blood test to look for genes linked to cerebellar hypoplasia or other genetic conditions.

The development of cerebellar hypoplasia isn’t fully understood, and it isn’t curable.

Treatment for cerebellar hypoplasia revolves around treating symptoms and supporting developmental delays. Treatment options include:

Cerebellar hypoplasia usually isn’t preventable because it’s often linked to gene mutations passed through families.

Taking steps to avoid tobacco, alcohol, and illegal drugs during pregnancy that can cause developmental issues for a fetus may help lower the chances of your baby being born with cerebellar hypoplasia.

Learn more about what to avoid during pregnancy.

The life expectancy for somebody with cerebellar hypoplasia depends on the severity of their condition. Some children might live typical lives with minimal to no apparent symptoms. Other children may not live through infancy or may have permanent disability.

Children with Dandy-Walker malformation are at a high risk of developing hydrocephalus, in which fluid builds up in the ventricles in the brain due to a blockage. About 50% of children with untreated hydrocephalus don’t survive to age 3, and only 20–23% live into adulthood.

But most children with treated Dandy-Walker malformation live into adulthood, according to the Child Neurology Foundation. Treatment of hydrocephalus in people with Dandy-Walker malformation appears to improve the outcomes.

About 30% of people with Dandy-Walker malformation also develop epilepsy.

Symptoms of cerebellar hypoplasia can vary widely between individuals, depending on the severity of the condition.

There’s no cure for cerebellar hypoplasia, but a doctor can recommend how to best manage complications, such as academic difficulties. It’s important to see a doctor for your child any time you suspect your child may have a neurological condition.