Agenesis of the Corpus Callosum (ACC)

What is agenesis of the corpus callosum?

Agenesis of the corpus callosum (ACC) is a congenital condition (present at birth) where you’re missing or partially missing the corpus callosum. This is a thick bundle of nerve fibers that connect the right and left hemispheres (sides) of your brain. It allows both sides of your brain to communicate with each other.

Think of your corpus callosum as a wooden bridge over a river. It allows people to move freely from one side of the river to the other. With agenesis of the corpus callosum, the bridge is missing planks or doesn’t exist. In some cases, you may still be able to cross the bridge, but it makes getting to the other side much more challenging.

The corpus callosum processes your senses, movement and advanced thinking. ACC can lead to symptoms like developmental delays, cognitive impairment or difficulty with fine motor skills, for example. Treatment is available to help manage symptoms.

What are the types of agenesis of the corpus callosum?

There are two types of ACC:

• Complete agenesis: All of your corpus callosum is missing.
• Partial agenesis (hypogenesis or dysgenesis): Part of your corpus callosum is missing.

Those types are further classified as:

• Isolated: It only affects your corpus callosum.
• Complex: It affects other parts of your brain beyond your corpus callosum.

What are the symptoms of agenesis of the corpus callosum?

Signs and symptoms of agenesis of the corpus callosum may include:

• Developmental delays (like rolling over, sitting up, walking, talking).
• Cognitive impairment or intellectual disability.
• Vision, hearing and speech challenges.
• Seizures.
• Feeding difficulty (infants).
• Tight or loose muscle tone.
• An abnormally large or small head size.
• Hydrocephalus (rare).

As a parent or caregiver, you might notice symptoms within your child’s first two years. Mild cases may not have obvious symptoms until your child reaches school age. For example, you might first notice that they have trouble with the following:

• Sensory-motor information (like catching a ball in the air).
• Cognitive speed (it takes your child longer than others to solve a puzzle).
• Reasoning and problem-solving (following multistep instructions).

The symptoms of ACC vary from person to person. They depend on how much of the corpus callosum is missing and whether the condition affects other parts of the brain.

What are the behavior problems associated with the agenesis of the corpus callosum?

The following are examples of behaviors that may happen with agenesis of the corpus callosum:

• Clumsiness (like tripping when walking).
• Difficulty coordinating the left and right sides of your body (like riding a bicycle or swimming).
• Difficulty with hand-eye coordination (like threading a needle or playing an instrument).
• Sleep issues (such as difficulty falling asleep, staying asleep or parasomnias).

Many children also experience neurodevelopmental disorders like ADHD with ACC.

What causes agenesis of the corpus callosum?

Healthcare providers aren’t entirely sure what causes the corpus callosum to not develop as expected. Research suggests a large majority are from an underlying genetic cause, including:

• Aneuploidy: Cells in your body have one extra or are missing chromosomes.
• Chromosomal rearrangements: The structure of a chromosome changes. For example, a segment breaks off and either rotates and reattaches to the same chromosome (inversion) or reattaches to another chromosome (translocation).
• Genetic variants: Changes to the DISC1 gene may lead to symptoms.

Does agenesis of the corpus callosum happen with other conditions?

Yes, some types of agenesis of the corpus callosum can occur with other congenital conditions (present at birth), such as:

• Aicardi syndrome.
• Apert syndrome.
• Dandy-Walker syndrome.
• Joubert syndrome.
• L1 syndrome.
• Schizencephaly.
• Trisomy 13.
• Trisomy 18.

What are the risk factors for agenesis of the corpus callosum?

Some pregnancy complications may affect how the fetus develops. This might increase the risk of agenesis of the corpus callosum. These include:

• Infection or injury to a fetus during the 12th to 24th week of pregnancy.
• Alcohol use disorder resulting in fetal alcohol syndrome.
• Phenylketonuria.

How is agenesis of the corpus callosum diagnosed?

A healthcare provider may suspect agenesis of the corpus callosum during an ultrasound after the 16th week of pregnancy. An official diagnosis usually happens after birth.

To do this, a healthcare provider will perform a physical exam and testing. During the exam, your provider will learn more about your symptoms and medical history. For children, a provider will ask parents or caregivers if their child is meeting developmental milestones for their age, like sitting upright on their own or walking.

Your provider may order imaging tests to confirm a diagnosis. Computed tomography (CT) or magnetic resonance imaging (MRI) will show whether the corpus callosum is missing or partially developed.

Other tests may be necessary if your provider suspects ACC occurs with another condition.

How is agenesis of the corpus callosum treated?

ACC treatment focuses on helping you manage symptoms. This could include:

• Taking antiseizure medications.
• Participating in early intervention or special education programs in school.
• Physical therapy.
• Occupational therapy.
• Speech therapy.
• Visual therapy.
• Inserting a shunt (for hydrocephalus).
• Cognitive behavioral therapy.

Treatment varies for each person. A healthcare provider will create a treatment that focuses on your needs.

Can agenesis of the corpus callosum be prevented?

As the cause isn’t well understood, there isn’t a way to prevent agenesis of the corpus callosum. Expecting parents can reduce their risk of having a child with ACC by taking care of themselves during pregnancy. This includes avoiding alcohol use and protecting yourself from infections or injury. A healthcare provider can help you manage your health and the fetus’s health.

Genetic testing is also available if you plan on expanding your family and want to learn more about your risk of having a child with a genetic condition.

What’s the prognosis for agenesis of the corpus callosum?

This condition affects each person differently. It can affect your cognitive function (thinking), motor skills and behavior. Your outlook varies based on how much of your corpus callosum is missing. This ranges in severity.

For some, ACC only has a minor effect on your everyday activities. For others, it needs lifelong management under the supervision of many different providers. Your provider can give you information on your outlook specifically, as it’s as unique as you are.

You may have trouble participating in sports or activities, learning in school or accomplishing your daily routine independently. This can affect your mental health and emotional well-being. A mental health professional, along with others on your care team, can help you adapt and manage how symptoms affect you.

What’s the life expectancy for agenesis of the corpus callosum?

Isolated ACC doesn’t directly affect your lifespan. But, your lifespan can vary if you have another condition with ACC or if symptoms affect other parts of your brain.

Can you live a normal life with agenesis of the corpus callosum?

Yes, this is possible. But what’s normal for you may be different from what someone else might consider normal. Your child can still play and participate in fun activities, go to school and socialize with others. You may face some challenges, but your healthcare providers can help you adapt if necessary.

When should I see a healthcare provider?

Talk to a healthcare provider if your child misses developmental milestones for their age or if anything seems “off” about your child’s behavior or functioning. You know your child best, so talk to their healthcare provider if you see signs of ACC.

What questions should I ask my healthcare provider?

Because ACC affects people in different ways, consider asking your healthcare provider:

• How much of the corpus callosum is missing?
• Is there another condition causing symptoms with ACC?
• What type of treatment do you recommend?
• Are there side effects of treatment?

Is agenesis of the corpus callosum a disability?

ACC can cause intellectual disability. But not all children have an intellectual disability with ACC. This varies based on how much of the corpus callosum is affected.