Medical Conditions

Agenesis of the Corpus Callosum (ACC)

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published NIH, NODCC, AAP guidelines

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If your baby has been diagnosed with or you suspect agenesis of the corpus callosum (acc), here is what the evidence says.

The short answer

Agenesis of the corpus callosum (ACC) is a condition in which the corpus callosum — the bundle of nerve fibers connecting the left and right hemispheres of the brain — fails to develop partially or completely. It occurs in approximately 1 in 4,000 births and is one of the most common brain malformations. ACC can be detected on prenatal ultrasound or postnatal MRI. Outcomes vary enormously: some individuals with isolated ACC have normal intelligence and minimal difficulties, while others (especially when ACC occurs alongside other brain abnormalities or genetic syndromes) may have significant developmental delays. The variability means that prenatal counseling and postnatal monitoring are both essential.

Key takeaways

  • Agenesis of the corpus callosum (ACC) is a condition in which the corpus callosum — the bundle of nerve fibers connecting the left and right hemispheres of the brain — fails to develop partially or completely. It occurs in approximately 1 in 4,000 births and is one of the most common brain malformations. ACC can be detected on prenatal ultrasound or postnatal MRI. Outcomes vary enormously: some individuals with isolated ACC have normal intelligence and minimal difficulties, while others (especially when ACC occurs alongside other brain abnormalities or genetic syndromes) may have significant developmental delays. The variability means that prenatal counseling and postnatal monitoring are both essential.
  • Usually normal when: Your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time
  • Call your doctor if: Your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition
  • Varies by age — see the age-by-age breakdown below
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Parents everywhere have the same worry. You are doing the right thing by looking into it.

What Parents Should Know

According to NIH, NODCC, AAP guidelines, agenesis of the corpus callosum (ACC) is a condition in which the corpus callosum — the bundle of nerve fibers connecting the left and right hemispheres of the brain — fails to develop partially or completely. It occurs in approximately 1 in 4,000 births and is one of the most common brain malformations. ACC can be detected on prenatal ultrasound or postnatal MRI. Outcomes vary enormously: some individuals with isolated ACC have normal intelligence and minimal difficulties, while others (especially when ACC occurs alongside other brain abnormalities or genetic syndromes) may have significant developmental delays. The variability means that prenatal counseling and postnatal monitoring are both essential. At Prenatal, aCC is often detected during routine prenatal ultrasound, typically in the second or third trimester, when the corpus callosum normally becomes visible. Signs include absence of the cavum septum pellucidum and widely spaced lateral ventricles (colpocephaly). Fetal MRI provides a more detailed view and helps identify whether the ACC is isolated or part of a broader brain malformation. Genetic testing (chromosomal microarray, exome sequencing) is often recommended to look for associated conditions such as Aicardi syndrome, Andermann syndrome, or other genetic syndromes. It is generally considered normal when your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time. However, you should contact your pediatrician promptly if your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time
Your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition
Your baby with ACC has a normal genetic workup and no seizures
Your baby with ACC has sudden changes in feeding, alertness, or head size — possible hydrocephalus or increased intracranial pressure requiring urgent imaging
Your child with ACC is learning and socializing appropriately for their age with supportive services
Your baby with ACC is not meeting motor or language milestones at expected ages
Prenatal imaging showed partial ACC but postnatal MRI shows no other abnormalities
You notice your child with ACC has difficulty with social interactions or understanding others' emotions

By Age

What to expect by age

Prenatal

ACC is often detected during routine prenatal ultrasound, typically in the second or third trimester, when the corpus callosum normally becomes visible. Signs include absence of the cavum septum pellucidum and widely spaced lateral ventricles (colpocephaly). Fetal MRI provides a more detailed view and helps identify whether the ACC is isolated or part of a broader brain malformation. Genetic testing (chromosomal microarray, exome sequencing) is often recommended to look for associated conditions such as Aicardi syndrome, Andermann syndrome, or other genetic syndromes.

0-6 months

Many babies with isolated ACC appear completely normal at birth and in the early months. Some may have feeding difficulties or seizures, particularly if ACC is part of a larger syndrome. A postnatal brain MRI confirms the diagnosis and helps characterize the extent (complete vs. partial ACC) and any associated brain anomalies. An ophthalmologic exam screens for eye abnormalities, which can occur in syndromic forms. Developmental monitoring begins, though it may be too early to determine long-term outcomes.

6-18 months

Motor milestones may be delayed in some children with ACC, though many achieve sitting and walking on a typical timeline. Social development is an important area to monitor, as some children with ACC have difficulty with social cognition and understanding nonverbal cues later in life. If seizures are present, management with a pediatric neurologist is important. Early intervention services (physical therapy, occupational therapy, speech therapy) should be started if any developmental delays are identified.

18 months - 5 years

Language development may be delayed, and some children with ACC have specific difficulty with complex language processing, abstract reasoning, and problem-solving. Social difficulties may become more apparent — children with ACC may struggle to read social cues, understand humor, or interpret figurative language. Many children with isolated ACC, however, perform within the normal range on developmental assessments. Neuropsychological testing around school age helps identify specific learning strengths and challenges to guide educational planning.

5+ years

Long-term outcomes for isolated ACC are highly variable. Many individuals lead independent lives with normal or near-normal intelligence, though they may have subtle difficulties with complex reasoning, social cognition, or multitasking. Those with ACC as part of a syndrome may have more significant intellectual disability. Ongoing educational support, social skills training, and periodic neuropsychological assessments help individuals reach their potential. The National Organization for Disorders of the Corpus Callosum (NODCC) provides valuable support and resources for families.

What to Tell Your Pediatrician

  • Describe when you first noticed agenesis of the corpus callosum (acc) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your baby with ACC is not meeting motor or language milestones at expected ages.
  • Mention if you notice your child with ACC has difficulty with social interactions or understanding others' emotions.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time
  • Your baby with ACC has a normal genetic workup and no seizures
  • Your child with ACC is learning and socializing appropriately for their age with supportive services
  • Prenatal imaging showed partial ACC but postnatal MRI shows no other abnormalities
Mention at your next visit when...
  • Your baby with ACC is not meeting motor or language milestones at expected ages
  • You notice your child with ACC has difficulty with social interactions or understanding others' emotions
  • Your child with ACC is struggling in school despite appearing bright in other areas
Act now when...
  • Your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition
  • Your baby with ACC has sudden changes in feeding, alertness, or head size — possible hydrocephalus or increased intracranial pressure requiring urgent imaging

What You Can Do at Home

  • Keep track of when you notice agenesis of the corpus callosum (acc) — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time — this is generally within the range of normal.
  • At Prenatal, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition.

Signs of Hydrocephalus in Babies

Hydrocephalus occurs when cerebrospinal fluid accumulates in the brain ventricles, causing increased pressure. In babies, the most noticeable sign is rapidly increasing head circumference (head growing faster than expected). Other signs include a bulging or tense fontanelle, prominent scalp veins, downward gaze of the eyes ("sunsetting"), irritability, vomiting, and developmental delays. Treatment typically involves surgical placement of a shunt or endoscopic third ventriculostomy to drain excess fluid.

My Baby Lost Skills They Previously Had

Temporary regression in skills can be normal during periods of rapid growth, illness, stress, or when a baby is intensely focused on developing a new skill. However, true developmental regression - the sustained loss of previously acquired skills such as words, social engagement, or motor abilities - is always a reason to seek prompt medical evaluation. This is especially concerning if multiple skill areas are affected simultaneously.

Early Signs of Epilepsy in Babies

Seizures in babies can look very different from seizures in older children or adults. Subtle signs may include repeated eye blinking or deviation, lip smacking, cycling leg movements, brief stiffening episodes, or clusters of head drops (infantile spasms). Infantile spasms are a neurological emergency that requires urgent evaluation. Not all unusual movements are seizures - babies commonly have benign tremors and startle reflexes - but any movement pattern that seems involuntary, repetitive, and cannot be interrupted deserves medical evaluation.

Lissencephaly (Smooth Brain) in Babies

Lissencephaly (meaning "smooth brain") is a rare brain malformation in which the brain surface lacks the normal folds (gyri) and grooves (sulci). It occurs when neurons fail to migrate to their proper positions during brain development between weeks 12-24 of pregnancy. Lissencephaly is classified as complete (agyria) or partial (pachygyria, with simplified, broad folds). It affects approximately 1 in 100,000 births and is typically caused by genetic mutations (most commonly in the LIS1 or DCX genes). Children with lissencephaly usually have severe developmental delays, epilepsy, and feeding difficulties, though the severity depends on the extent of brain involvement.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is agenesis of the corpus callosum (acc) normal?
Agenesis of the corpus callosum (ACC) is a condition in which the corpus callosum — the bundle of nerve fibers connecting the left and right hemispheres of the brain — fails to develop partially or completely. It occurs in approximately 1 in 4,000 births and is one of the most common brain malformations. ACC can be detected on prenatal ultrasound or postnatal MRI. Outcomes vary enormously: some individuals with isolated ACC have normal intelligence and minimal difficulties, while others (especially when ACC occurs alongside other brain abnormalities or genetic syndromes) may have significant developmental delays. The variability means that prenatal counseling and postnatal monitoring are both essential.
When should I call the doctor about agenesis of the corpus callosum (acc)?
Your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition Your baby with ACC has sudden changes in feeding, alertness, or head size — possible hydrocephalus or increased intracranial pressure requiring urgent imaging
When is agenesis of the corpus callosum (acc) normal?
Your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time Your baby with ACC has a normal genetic workup and no seizures Your child with ACC is learning and socializing appropriately for their age with supportive services
What causes agenesis of the corpus callosum (acc)?
Agenesis of the corpus callosum (ACC) is a condition in which the corpus callosum — the bundle of nerve fibers connecting the left and right hemispheres of the brain — fails to develop partially or completely. It occurs in approximately 1 in 4,000 births and is one of the most common brain malformations. ACC can be detected on prenatal ultrasound or postnatal MRI. Outcomes vary enormously: some individuals with isolated ACC have normal intelligence and minimal difficulties, while others (especially when ACC occurs alongside other brain abnormalities or genetic syndromes) may have significant developmental delays. The variability means that prenatal counseling and postnatal monitoring are both essential. Common explanations include: Your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time. Your baby with ACC has a normal genetic workup and no seizures.
What should I mention to my pediatrician about agenesis of the corpus callosum (acc)?
You should mention agenesis of the corpus callosum (acc) at your next visit if: Your baby with ACC is not meeting motor or language milestones at expected ages. You notice your child with ACC has difficulty with social interactions or understanding others' emotions. Your child with ACC is struggling in school despite appearing bright in other areas.
Is agenesis of the corpus callosum (acc) normal at Prenatal?
ACC is often detected during routine prenatal ultrasound, typically in the second or third trimester, when the corpus callosum normally becomes visible. Signs include absence of the cavum septum pellucidum and widely spaced lateral ventricles (colpocephaly). Fetal MRI provides a more detailed view and helps identify whether the ACC is isolated or part of a broader brain malformation. Genetic testing (chromosomal microarray, exome sequencing) is often recommended to look for associated conditions such as Aicardi syndrome, Andermann syndrome, or other genetic syndromes.
Is agenesis of the corpus callosum (acc) normal at 0-6 months?
Many babies with isolated ACC appear completely normal at birth and in the early months. Some may have feeding difficulties or seizures, particularly if ACC is part of a larger syndrome. A postnatal brain MRI confirms the diagnosis and helps characterize the extent (complete vs. partial ACC) and any associated brain anomalies. An ophthalmologic exam screens for eye abnormalities, which can occur in syndromic forms. Developmental monitoring begins, though it may be too early to determine long-term outcomes.
Should I go to the ER for agenesis of the corpus callosum (acc)?
Seek emergency care if your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition, or if your baby with ACC has sudden changes in feeding, alertness, or head size — possible hydrocephalus or increased intracranial pressure requiring urgent imaging. When in doubt, call your pediatrician's after-hours line for guidance.
Does agenesis of the corpus callosum (acc) go away on its own?
In many cases, agenesis of the corpus callosum (acc) resolves on its own, especially when your baby has isolated ACC (no other brain abnormalities) and is meeting developmental milestones on time. By 5+ years, long-term outcomes for isolated ACC are highly variable. Many individuals lead independent lives with normal or near-normal intelligence, though they may have subtle difficulties with complex reasoning, social cognition, or multitasking. Those with ACC as part of a syndrome may have more significant intellectual disability. Ongoing educational support, social skills training, and periodic neuropsychological assessments help individuals reach their potential. The National Organization for Disorders of the Corpus Callosum (NODCC) provides valuable support and resources for families.
NIHNODCCAAP

References

  1. [1]National Institute of Neurological Disorders and Stroke. Agenesis of the Corpus Callosum. NINDS, 2023. NIH
  2. [2]National Organization for Disorders of the Corpus Callosum. About ACC. NODCC, 2024. NODCC
  3. [3]Paul LK, Brown WS, Adolphs R, et al. Agenesis of the Corpus Callosum: Genetic, Developmental, and Functional Aspects of Connectivity. Nature Reviews Neuroscience. 2007;8:287-299. AAP

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Agenesis of the Corpus Callosum (ACC).

Things to mention

  • Describe when you first noticed agenesis of the corpus callosum (acc) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your baby with ACC is not meeting motor or language milestones at expected ages.
  • Mention if you notice your child with ACC has difficulty with social interactions or understanding others' emotions.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your baby with ACC is not meeting motor or language milestones at expected ages
  • You notice your child with ACC has difficulty with social interactions or understanding others' emotions
  • Your child with ACC is struggling in school despite appearing bright in other areas

Urgent signs to report immediately

  • Your baby with ACC develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition
  • Your baby with ACC has sudden changes in feeding, alertness, or head size — possible hydrocephalus or increased intracranial pressure requiring urgent imaging

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

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Bottom line

Most cases of agenesis of the corpus callosum (acc) are normal. Talk to your pediatrician if your baby with acc develops seizures — seek prompt neurological evaluation, as seizures can indicate a more complex underlying condition.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Signs of Hydrocephalus in Babies

Hydrocephalus occurs when cerebrospinal fluid accumulates in the brain ventricles, causing increased pressure. In babies, the most noticeable sign is rapidly increasing head circumference (head growing faster than expected). Other signs include a bulging or tense fontanelle, prominent scalp veins, downward gaze of the eyes ("sunsetting"), irritability, vomiting, and developmental delays. Treatment typically involves surgical placement of a shunt or endoscopic third ventriculostomy to drain excess fluid.

My Baby Lost Skills They Previously Had

Temporary regression in skills can be normal during periods of rapid growth, illness, stress, or when a baby is intensely focused on developing a new skill. However, true developmental regression - the sustained loss of previously acquired skills such as words, social engagement, or motor abilities - is always a reason to seek prompt medical evaluation. This is especially concerning if multiple skill areas are affected simultaneously.

Early Signs of Epilepsy in Babies

Seizures in babies can look very different from seizures in older children or adults. Subtle signs may include repeated eye blinking or deviation, lip smacking, cycling leg movements, brief stiffening episodes, or clusters of head drops (infantile spasms). Infantile spasms are a neurological emergency that requires urgent evaluation. Not all unusual movements are seizures - babies commonly have benign tremors and startle reflexes - but any movement pattern that seems involuntary, repetitive, and cannot be interrupted deserves medical evaluation.

Lissencephaly (Smooth Brain) in Babies

Lissencephaly (meaning "smooth brain") is a rare brain malformation in which the brain surface lacks the normal folds (gyri) and grooves (sulci). It occurs when neurons fail to migrate to their proper positions during brain development between weeks 12-24 of pregnancy. Lissencephaly is classified as complete (agyria) or partial (pachygyria, with simplified, broad folds). It affects approximately 1 in 100,000 births and is typically caused by genetic mutations (most commonly in the LIS1 or DCX genes). Children with lissencephaly usually have severe developmental delays, epilepsy, and feeding difficulties, though the severity depends on the extent of brain involvement.

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