Agenesis of the Corpus Callosum (ACC)
What is agenesis of the corpus callosum?
Agenesis of the corpus callosum (ACC) is a birth defect that affects the brain. A person with ACC has a missing or partially missing corpus callosum. The corpus callosum is a thick bundle of nerve fibers that connects the right and left hemispheres (halves) of the brain. It allows both sides of the brain to communicate with each other.
How does an absent corpus callosum affect a person?
The effects of ACC can be subtle or severe. It depends on how much of the corpus callosum is missing and whether there are any other problems with the brain. Some experience mild social, emotional or mental effects. Others may have severe impairments or seizures.
Is ACC associated with other disorders?
An absent corpus callosum can occur by itself but is sometimes associated with other congenital disorders (defects present at birth), such as:
- Aicardi syndrome.
- Andermann syndrome (damage to the nerves that control the muscles).
- Chiari malformation.
- Dandy-Walker syndrome.
- Holoprosencephaly (failure of the brain to split into two hemispheres).
- Schizencephaly (slits in the hemispheres of the brain).
- Spina bifida.
How common is agenesis of the corpus callosum?
ACC is the most common congenital defect of the brain. But it is still rare, affecting only 0.05 to 0.07% of the population.
Symptoms and Causes
What causes agenesis of the corpus callosum?
Scientists don’t fully understand the causes of ACC, but it has been associated with:
- Genetic inheritance.
- Fetal alcohol syndrome.
- Infection or injury to a fetus during the 12th to 24th week of pregnancy.
What are the symptoms of a missing corpus callosum?
The signs and symptoms of ACC vary. It depends on how much of the corpus callosum is missing and the presence of any other associated disorders.
The signs often show up during the first two years of life, but mild cases are sometimes not noticed for many years.
Symptoms might include:
- Epileptic seizures.
- Developmental delays (for example, holding up the head, sitting, standing, walking).
- Feeding problems.
- Hearing or vision impairment.
- Problems with hand-eye coordination or between the right and left sides of the body.
- Problems with social interactions.
- Repetitive speech.
Some people with ACC can also have physical signs of the disorder:
- Abnormally shaped nose or ears.
- Bent fingers.
- Deep-set or wide-set eyes.
- Lack of muscle tone.
- Larger forehead.
- Skin tags.
- Unusually small or large head.
Diagnosis and Tests
How is an absent corpus callosum diagnosed?
If a healthcare provider suspects that you or your child have ACC, you will need a physical examination. The healthcare provider will talk to you about any symptoms and developmental delays, then examine the body.
Your provider will order imaging tests to take pictures inside the head. Computed tomography (CT) or magnetic resonance imaging (MRI) will show whether the corpus callosum is missing or partially developed.
Management and Treatment
How is agenesis of the corpus callosum treated?
Treatment for an absent corpus callosum depends on how the disorder affects an individual. It often includes:
- Genetic counseling to determine whether the disorder runs in the family.
- Medications to prevent seizures.
- Physical therapy to minimize developmental delays or problems with movement.
- Shunt in the brain to drain fluid, in the case of hydrocephalus.
- Special education to address intellectual issues.
- Speech therapy.
Can I prevent agenesis of the corpus callosum?
It’s not entirely possible to prevent ACC. Pregnant women can reduce the risk of congenital defects by avoiding alcohol, infection or injury.
Outlook / Prognosis
What is the outlook for people with agenesis of the corpus callosum?
The outlook for a person with ACC depends on how severe the condition is. Many children with ACC lead normal lives with only minor effects. Others need medications to prevent seizures and therapy to improve function. For those who have an intellectual disability, it does not get worse over time.
ACC doesn’t usually cause death.
What else can 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?
- Should anyone in our family get genetic testing?
- Should we consider antiseizure medication?
- Should we get speech therapy, physical therapy or another kind of therapy?
A note from Cleveland Clinic
Agenesis of the corpus callosum, a brain defect present at birth, can be mild or severe. It’s usually not fatal, and specific therapies can help. Although the disorder is generally diagnosed in the first two years of life, some cases are diagnosed later. Talk to your healthcare provider if you or your child are experiencing any troubling symptoms.
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