Cranial asymmetry, or flat head syndrome, is an uneven head shape in infants, affecting about one in five babies. It appears when a baby is a few months old and results from spending extensive time lying on their back. An infant’s skull is soft and malleable, so this constant pressure can alter its shape. This change is cosmetic and does not affect brain development, cause pain, or interfere with a baby’s overall growth.
Common Causes of an Uneven Head Shape
A newborn’s skull bones are soft and separated by fibrous sutures, allowing the head to mold during birth and accommodate brain growth. This pliability makes the skull susceptible to external pressure. The most common cause is the baby’s sleeping position, as the “Back to Sleep” campaign to reduce SIDS risk means infants spend many hours on their backs.
Congenital muscular torticollis is another common cause. This condition involves a tight neck muscle that causes an infant to tilt their head or prefer turning it to one side. This consistent head preference leads to localized flattening. For example, a child with torticollis on the left side of their neck will often develop flattening on the right side of their head.
Other circumstances can contribute to cranial asymmetry. A cramped position in the womb, common in multiple births, can play a role. Premature infants are more susceptible due to softer skulls and less ability to change head position. An assisted delivery using forceps or a vacuum can also mold the head, though this often resolves within weeks.
Distinguishing Between Positional and Structural Asymmetry
Positional asymmetry, including plagiocephaly (side flattening) and brachycephaly (back flattening), is an external shaping issue. It does not involve premature fusion of the skull’s sutures or restrict brain development. When viewed from above, a head with positional plagiocephaly may look like a parallelogram, with the ear on the flattened side pushed forward. This condition is cosmetic and often improves over time.
Structural asymmetry is caused by craniosynostosis, a rare condition affecting about 1 in 2,000 babies where skull sutures fuse too early. This premature fusion prevents the skull from expanding to accommodate the growing brain. Craniosynostosis can restrict brain growth, distort the face and skull, and may require surgical intervention.
The physical presentation differs between the two conditions. With craniosynostosis, a prominent ridge may be felt on the skull where a suture has fused. For example, if the lambdoid suture at the back of the head fuses, it can cause a bump behind the ear. A pediatrician can distinguish between them with a physical exam, but an X-ray or CT scan may be used to confirm the diagnosis.
Management and Treatment Strategies
Most cases of positional plagiocephaly are managed with simple strategies at home. The primary approach is repositioning to relieve pressure on the flattened area of the skull. This includes alternating the baby’s head position during sleep, such as by changing which end of the crib their head is at each night. This encourages them to turn their head in different directions to face light or activity.
Supervised “tummy time” is also important. Placing a baby on their stomach while awake strengthens neck, back, and arm muscles, which helps correct the flat spot and promotes motor skills. Limiting time an infant spends in car seats, swings, and bouncy seats while awake also reduces pressure on the back of the head.
If muscular torticollis is the cause, a pediatrician may recommend physical therapy. A therapist can teach parents stretching and strengthening exercises to lengthen the tight neck muscles, allowing the baby to turn their head more freely. Early intervention with physical therapy can correct both the torticollis and the associated head flattening.
For moderate to severe cases that do not improve with other strategies, a cranial orthotic device, or helmet, may be prescribed. These custom-fitted helmets are worn up to 23 hours a day, applying gentle, persistent pressure to guide the skull’s growth. The helmet is loose over the flat areas to allow for growth while remaining snug over prominent areas to redirect it. This therapy is most effective when started between 6 and 7 months of age and is less beneficial for infants over 10 months old.
When to Seek a Medical Evaluation
Parents should feel comfortable bringing up any concerns about their baby’s head shape during regular well-child visits. A pediatrician can visually diagnose plagiocephaly and provide early advice to prevent it from worsening. Schedule an evaluation if you notice your baby has a strong preference for turning their head to one side, has difficulty turning it, or if a flat spot has not improved by two months of age.
Contact your pediatrician promptly if you notice an unusual head shape, a hard ridge on the skull, or a lack of improvement despite repositioning efforts. These could be signs of craniosynostosis, which requires a different management approach. It is better to seek a professional opinion than to wait and see.
During an evaluation, a healthcare provider will perform a physical examination and may take measurements to assess the asymmetry. If craniosynostosis is suspected or the diagnosis is uncertain, your pediatrician may refer you to a specialist. This could be a craniofacial expert or a pediatric neurosurgeon for a more thorough assessment.