Lissencephaly (Smooth Brain) in Babies
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published NIH, AAP guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect lissencephaly (smooth brain) in babies, here is what the evidence says.
The short answer
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.
Key takeaways
- 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.
- Usually normal when: Your baby has a brain MRI that shows normal gyral (folding) patterns, even if ordered for other concerns
- Call your doctor if: Your baby with lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia)
- Varies by age — see the age-by-age breakdown below
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What Parents Should Know
According to NIH, AAP guidelines, 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. At 0-3 months, babies with lissencephaly may appear relatively normal at birth, or microcephaly (small head) may be present. Early signs include poor feeding, weak suck, difficulty swallowing, and hypotonia (low muscle tone). Seizures can begin in the neonatal period, including infantile spasms. The diagnosis is typically confirmed by brain MRI, which shows a smooth or nearly smooth brain surface. Genetic testing helps identify the specific mutation and associated syndrome (such as Miller-Dieker syndrome with LIS1 deletion, or X-linked lissencephaly with DCX mutations). It is generally considered normal when your baby has a brain MRI that shows normal gyral (folding) patterns, even if ordered for other concerns. However, you should contact your pediatrician promptly if your baby with lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia).
Normal vs. Concerning
By Age
What to expect by age
0-3 months
Babies with lissencephaly may appear relatively normal at birth, or microcephaly (small head) may be present. Early signs include poor feeding, weak suck, difficulty swallowing, and hypotonia (low muscle tone). Seizures can begin in the neonatal period, including infantile spasms. The diagnosis is typically confirmed by brain MRI, which shows a smooth or nearly smooth brain surface. Genetic testing helps identify the specific mutation and associated syndrome (such as Miller-Dieker syndrome with LIS1 deletion, or X-linked lissencephaly with DCX mutations).
3-12 months
Developmental delays become increasingly apparent during this period. Most babies with classical lissencephaly do not achieve independent head control or sitting. Seizures, including infantile spasms, occur in the majority of affected children and can be difficult to control. Spasticity (increased muscle tone) may develop, replacing the initial hypotonia. Feeding difficulties often worsen, and many children require specialized feeding support. A gastrostomy tube (G-tube) may be recommended to ensure adequate nutrition and reduce aspiration risk.
1-3 years
Children with severe (grade 1-2) lissencephaly have profound intellectual and motor disability. Epilepsy management is a primary focus of care, often requiring multiple anti-seizure medications. Some children with partial lissencephaly (pachygyria) may achieve more motor milestones, such as supported sitting or rolling. Respiratory infections are a common complication due to aspiration risk and weak cough. Supportive care, including chest physiotherapy and careful feeding management, improves quality of life.
3+ years
Long-term prognosis depends on the severity and extent of the brain malformation. Children with milder forms (grade 3-4 with more preserved gyral pattern) may have better outcomes. Ongoing multidisciplinary care includes neurology, gastroenterology, pulmonology, orthopedics, and palliative care as appropriate. Despite severe limitations, children with lissencephaly are aware of and responsive to their environment, enjoy social interaction, and benefit from sensory stimulation and engagement. Family support and respite care are essential components of comprehensive management.
What to Tell Your Pediatrician
- Describe when you first noticed lissencephaly (smooth brain) in babies 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 has severe developmental delays with poor head control, difficulty feeding, and early-onset seizures.
- Mention if your baby was diagnosed with lissencephaly prenatally and you need postnatal evaluation and care planning.
- 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
- Your baby has a brain MRI that shows normal gyral (folding) patterns, even if ordered for other concerns
- Your baby has mild developmental delays but brain imaging is normal — lissencephaly is ruled out
- Your child has partial lissencephaly with a milder pattern and is making steady, measurable progress with therapy
- Your baby has severe developmental delays with poor head control, difficulty feeding, and early-onset seizures
- Your baby was diagnosed with lissencephaly prenatally and you need postnatal evaluation and care planning
- Your child with lissencephaly is having worsening seizures or new feeding difficulties
- You have a family history of lissencephaly and are seeking genetic counseling
- Your baby with lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia)
- Your baby with lissencephaly becomes unusually unresponsive, has a bulging fontanelle, or develops persistent vomiting — possible increased intracranial pressure or other acute complication
What You Can Do at Home
- Keep track of when you notice lissencephaly (smooth brain) in babies — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby has a brain MRI that shows normal gyral (folding) patterns, even if ordered for other concerns — this is generally within the range of normal.
- At 0-3 months, 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 lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia).
Related Conditions
Infantile Spasms (West Syndrome)
Infantile spasms (West syndrome) are a serious type of epilepsy that typically begins between 3-12 months of age, affecting about 1 in 2,000 to 4,000 babies. Spasms often appear as sudden, brief stiffening or jerking movements that occur in clusters, especially upon waking. Rapid diagnosis and treatment (typically within days) are critical, as early treatment with ACTH or vigabatrin significantly improves developmental outcomes. If you suspect infantile spasms, seek medical evaluation immediately.
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.
My Baby's Head Seems Too Small (Microcephaly)
A baby's head circumference is measured at every well-child visit to track brain growth. A head that is smaller than expected does not always mean there is a problem - genetics play a major role, and some families naturally have smaller head sizes. However, if the head circumference is significantly below normal or is falling off its growth curve, your pediatrician will want to investigate further.
My Baby Seems Floppy (Hypotonia)
A "floppy" baby is one whose muscles feel unusually relaxed and who may slip through your hands when you lift them under the arms. Many cases of mild floppiness improve on their own as your baby grows stronger, but it is important to have your pediatrician evaluate your baby to rule out any underlying conditions.
Related Resources
Frequently asked questions
Is lissencephaly (smooth brain) in babies normal?
When should I call the doctor about lissencephaly (smooth brain) in babies?
When is lissencephaly (smooth brain) in babies normal?
What causes lissencephaly (smooth brain) in babies?
What should I mention to my pediatrician about lissencephaly (smooth brain) in babies?
Is lissencephaly (smooth brain) in babies normal at 0-3 months?
Is lissencephaly (smooth brain) in babies normal at 3-12 months?
Should I go to the ER for lissencephaly (smooth brain) in babies?
Does lissencephaly (smooth brain) in babies go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Lissencephaly (Smooth Brain) in Babies.
Things to mention
- Describe when you first noticed lissencephaly (smooth brain) in babies 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 has severe developmental delays with poor head control, difficulty feeding, and early-onset seizures.
- Mention if your baby was diagnosed with lissencephaly prenatally and you need postnatal evaluation and care planning.
- 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 has severe developmental delays with poor head control, difficulty feeding, and early-onset seizures
- Your baby was diagnosed with lissencephaly prenatally and you need postnatal evaluation and care planning
- Your child with lissencephaly is having worsening seizures or new feeding difficulties
Urgent signs to report immediately
- Your baby with lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia)
- Your baby with lissencephaly becomes unusually unresponsive, has a bulging fontanelle, or develops persistent vomiting — possible increased intracranial pressure or other acute complication
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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Related Resources
Bottom line
Most cases of lissencephaly (smooth brain) in babies are normal. Talk to your pediatrician if your baby with lissencephaly develops prolonged seizures, difficulty breathing, or signs of aspiration (choking, color changes during feeding, recurrent pneumonia).
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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Related Medical Concerns
Infantile Spasms (West Syndrome)
Infantile spasms (West syndrome) are a serious type of epilepsy that typically begins between 3-12 months of age, affecting about 1 in 2,000 to 4,000 babies. Spasms often appear as sudden, brief stiffening or jerking movements that occur in clusters, especially upon waking. Rapid diagnosis and treatment (typically within days) are critical, as early treatment with ACTH or vigabatrin significantly improves developmental outcomes. If you suspect infantile spasms, seek medical evaluation immediately.
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.
My Baby's Head Seems Too Small (Microcephaly)
A baby's head circumference is measured at every well-child visit to track brain growth. A head that is smaller than expected does not always mean there is a problem - genetics play a major role, and some families naturally have smaller head sizes. However, if the head circumference is significantly below normal or is falling off its growth curve, your pediatrician will want to investigate further.
My Baby Seems Floppy (Hypotonia)
A "floppy" baby is one whose muscles feel unusually relaxed and who may slip through your hands when you lift them under the arms. Many cases of mild floppiness improve on their own as your baby grows stronger, but it is important to have your pediatrician evaluate your baby to rule out any underlying conditions.
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.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.