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Agenesis of the Corpus Callosum


Agenesis of the corpus callosum (ACC) is a birth defect of the brain. In ACC, the corpus callosum (a thick band of nerves that connects the brain's left and right sides) is either partly or fully missing. (Agenesis means a failure to develop.) The causes of ACC aren't fully understood, but it has been linked to fetal alcohol syndrome, certain inherited genetic disorders, and infections or injuries that occur between the 12th and 22nd weeks of pregnancy, when the corpus callosum is developing.

ACC is rare, affecting about 1 in 4,000 infants born in the United States. It's usually diagnosed before age 2, but mild cases may go undiagnosed until adulthood. ACC can occur on its own or alongside other brain abnormalities. These may include malformations such as schizencephaly (clefts in the brain tissue) and holoprosencephaly (failure of the brain to separate into separate hemispheres).

ACC symptoms can range from mild to severe. Some patients have seizures and significant developmental impairments, while others have only mild neurological symptoms, such as problems with vision, hearing or coordination. Some patients have no symptoms.

The UCSF Fetal Treatment Center is a world leader in diagnosing birth defects, such as ACC, before delivery. Our experience with both traditional and minimally invasive fetal surgery is unparalleled. We also provide follow-up support to our patients, with our specialists working collaboratively to maximize each child's physical, mental and social development.

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To request an appointment, please call the Fetal Treatment Center.

San Francisco


Signs & symptoms

ACC symptoms range from mild to severe. They fall into the following categories:

Sensory problems

  • Hearing impairment
  • Vision impairment

Motor problems

  • Developmental delays in infancy and early childhood (affecting milestones, such as sitting, standing and walking)
  • Problems with hand-eye coordination or coordination between the body's right and left sides
  • Low muscle tone
  • Spasticity (abnormal posture, motions or reflexes)

Intellectual problems

  • Developmental delays in language or social behavior
  • Learning disabilities
  • Language deficits
  • Intellectual disability

Other neurological problems

  • Epilepsy
  • Hydrocephalus (an abnormal buildup of fluid in the brain)
  • Headaches
  • Trouble swallowing
  • Sleep disruptions

Some people with ACC have differences of appearance related to the condition. These may include:

  • Unusually small or large head
  • Unusually large forehead
  • One or more bent fingers
  • Skin tags in front of the ears
  • Wide-set or deep-set eyes


ACC may be diagnosed before birth. If a problem with the corpus callosum is detected during a routine prenatal ultrasound, you'll be referred for additional tests. These may include:

  • Fetal anatomy survey. This high-resolution ultrasound provides a more detailed picture of the developing fetus and can help doctors check for other abnormalities.
  • Fetal MRI. This test uses a powerful magnet to safely create an image of the fetus, providing a detailed view of organs, such as the brain.
  • Amniocentesis. A sample of the amniotic fluid is analyzed to help identify birth defects, genetic problems or infections that can affect fetal growth.

Someone with a mild case of ACC may not be diagnosed until childhood, adolescence or adulthood, depending on whether and when learning or neurological problems emerge. After conducting a physical exam, the doctor will order an MRI scan to obtain images of the brain.


Care involves managing symptoms and providing support to maximize each patient's physical, cognitive and social development and function. Customized to meet individual needs, treatment plans may include:

  • Regular appointments to monitor health, growth and development
  • Medications to control seizures
  • Physical therapy to support motor development
  • Occupational therapy to support mental and social development
  • Speech therapy

Where to get care (1)

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Fetal Treatment Center

Fetal Treatment Center

San Francisco / Oakland

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Early Anatomy Evaluation Program

UCSF offers advanced prenatal imaging to evaluate fetal development and identify abnormalities early in pregnancy.

Fetal Neurology Center of Excellence

Our specialists, leaders in the new field of fetal neurology, can provide prenatal diagnoses of birth defects that may affect the baby's nervous system.

Awards & recognition

  • Top 10 in the nation for neonatology

  • Ranked among the nation's best in 10 specialties

  • successful open fetal surgery in the world

  • in number of fetal surgery clinical trials