Can skull bones be asymmetrical? A closer look at cranial asymmetry

September 27, 2025 •

4 min read

It is a common misconception that a perfectly symmetrical head is the norm, but in reality, some degree of asymmetry is common and natural. The question, Can skull bones be asymmetrical?, can be answered with a resounding yes, though the reasons behind it vary significantly, from common positional issues in infants to more serious, rare conditions.

Quick Summary

Yes, skull bones can be asymmetrical due to a range of factors, including normal development variations, infant head positioning (plagiocephaly), or premature fusion of skull plates (craniosynostosis). While some asymmetry is natural, noticeable or sudden changes warrant medical evaluation to rule out underlying issues.

Key Points

Skull Asymmetry is Normal: A perfectly symmetrical skull is rare, and minor variations are a natural part of human anatomy, both in infants and adults.
Positional Plagiocephaly is Common: The most frequent cause of an asymmetrical head in babies is positional plagiocephaly, which results from constant pressure on one part of the soft skull.
Craniosynostosis is Rare but Serious: In contrast, craniosynostosis is a congenital condition where skull bones fuse too early, potentially requiring surgery to allow for proper brain growth.
Helmet Therapy is an Option: For moderate to severe plagiocephaly that doesn't improve with repositioning, a cranial orthotic helmet can be used to reshape the infant's skull.
Know When to See a Doctor: Persistent or worsening asymmetry in an infant, or a new change in an adult's skull shape, should prompt a medical evaluation to rule out serious underlying issues.
Plagiocephaly Does Not Harm Brain Development: Positional flattening is a cosmetic issue and does not affect a child's neurological development or intelligence.

Normal skull variations and mild asymmetry

Every human skull has some natural variation, and no person is perfectly symmetrical. Minor differences between the left and right sides of the face and skull are normal and often go unnoticed. These subtle differences can be influenced by genetics, growth patterns, and minor lifestyle habits over time. It is a common misconception that perfect symmetry is the hallmark of health, but often, these slight asymmetries are simply a part of a person's unique anatomical makeup and are not a cause for medical concern. Think of it like fingerprints; every person's bone structure is slightly different.

Infant head shape concerns: Positional plagiocephaly

The most common cause of asymmetrical skull shape in infants is positional plagiocephaly, or "flat head syndrome." This condition occurs because a newborn's skull bones are soft and not yet fused, making them susceptible to pressure. The increase in this condition is linked to the "Back to Sleep" campaign, which successfully reduced Sudden Infant Death Syndrome (SIDS) by encouraging parents to place infants on their backs to sleep. While crucial for safety, this can lead to a flattened area on one side of the back of the head if the baby consistently rests in the same position.

Causes of positional plagiocephaly:

Sleep position: Constant pressure on one area of the skull during sleep.
Womb position: Crowding in the womb, especially with multiple births, can cause a misshapen head at birth.
Muscular torticollis: A tight neck muscle on one side can cause the baby to consistently favor turning their head in one direction.

More serious condition: Craniosynostosis

In a small number of cases, an asymmetrical skull is caused by a more serious condition called craniosynostosis. This occurs when one or more of the fibrous joints, or sutures, in an infant's skull fuse prematurely, limiting normal brain and skull growth in the affected area. Unlike positional plagiocephaly, craniosynostosis is not caused by external pressure and may require surgical correction to prevent complications.

Characteristics of craniosynostosis:

An abnormal head shape is often noticeable at or soon after birth.
A firm, raised ridge may be felt along the prematurely fused suture.
Changes in the eyes or face, such as bulging of the forehead or uneven eye sockets, can occur.
It can sometimes be part of a genetic syndrome.

Comparison of plagiocephaly and craniosynostosis

Understanding the difference between these two conditions is crucial for proper diagnosis and treatment. While both cause skull asymmetry, their origins and treatments differ significantly.


Feature	Positional Plagiocephaly	Craniosynostosis
Cause	External pressure on the soft skull.	Premature fusion of one or more skull sutures.
Sutures	Sutures remain open and flexible.	One or more sutures are prematurely fused.
Severity	Mild to severe, but cosmetic and not usually a health risk.	Can lead to increased intracranial pressure, requiring surgical intervention.
Treatment	Repositioning, tummy time, and helmet therapy.	Typically requires surgery to release the fused sutures.
Affected Age	Infants, typically most noticeable in the first few months.	At or soon after birth, often a congenital condition.
Prognosis	Excellent; most cases improve with conservative management.	Good, especially with early surgical intervention to allow proper brain growth.

Asymmetry in adults

While skull asymmetry is a significant concern in infants, adults can also have variations in skull shape. These are often the result of natural growth patterns from childhood and are generally not cause for alarm. However, a new or rapidly progressing change in skull shape in an adult could indicate an underlying medical condition, such as a trauma or a rare bone disorder. If you notice a new dent, bump, or significant change, it is important to consult a healthcare provider for an evaluation. Conditions like Paget's disease or certain bone-destructive cancers are rare but can affect skull structure.

When to seek medical advice

It's important for parents to monitor their baby's head shape. While mild positional plagiocephaly often resolves on its own, a professional evaluation is warranted if the asymmetry is persistent or seems to be worsening. A pediatrician can help distinguish between common positional flattening and craniosynostosis, which requires more specific care. A physical exam is usually the first step, and in some cases, imaging tests like X-rays or CT scans may be ordered to confirm a diagnosis.

Treatment options for infant cranial asymmetry

For babies with positional plagiocephaly, treatment focuses on reducing pressure on the flattened area and encouraging growth in the correct direction.

Non-surgical options:

Repositioning: Frequently changing the baby's head position while they are asleep and awake.
"Tummy time": Supervised time on the stomach while the baby is awake helps strengthen neck and shoulder muscles.
Reducing time in carriers: Limiting the amount of time the baby spends in car seats, swings, or bouncers can reduce consistent pressure on the back of the head.
Physical therapy: Can be effective if the asymmetry is linked to muscular torticollis by stretching and strengthening neck muscles.

Cranial orthosis (helmet therapy):

If non-surgical methods are not effective for moderate to severe cases, a cranial orthotic helmet may be recommended. This custom-fitted helmet gently redirects skull growth as the infant's brain expands. Treatment is most effective between 4 and 8 months of age when the skull is still growing rapidly.

Conclusion: Understanding skull asymmetry

In conclusion, it is normal for skull bones to be asymmetrical, and minor variations are a part of human anatomy. For infants, the most common type of asymmetry is positional plagiocephaly, which is highly treatable with conservative methods like repositioning and tummy time. In rarer instances, it can signal a more serious issue like craniosynostosis, which requires specialized medical care. For adults, new or sudden changes in skull shape should always be evaluated by a healthcare professional. Understanding these distinctions is key to ensuring proper management and care for cranial asymmetry. For more in-depth information on newborn head shape concerns, you can refer to authoritative sources like HealthyChildren.org.

Frequently Asked Questions

Yes, it is very common. Many babies are born with a slightly misshapen head due to the birthing process, and others develop positional plagiocephaly from spending too much time in one position. Mild cases often improve on their own.

Plagiocephaly is a cosmetic flattening caused by external pressure on the skull, while craniosynostosis is the premature fusion of skull sutures, which can restrict brain growth and may require surgery.

Yes, many adults have minor, natural asymmetries from childhood development. However, a new or sudden change in an adult's skull shape should be evaluated by a doctor to rule out trauma or other medical conditions.

Yes, for moderate to severe cases, a custom-fitted cranial orthotic helmet can be very effective, especially when started between 4 and 8 months of age when the skull is growing fastest.

Tummy time is supervised playtime where an infant lies on their stomach while awake. It helps build neck and shoulder strength and gives the back of the head a break from pressure, aiding in the correction of flat spots.

You should see a pediatrician if your baby's head shape is not improving with repositioning, seems to be worsening, or if you notice a firm ridge along a suture line. Early evaluation is important.

Positional plagiocephaly does not typically affect a child's brain development or cause intellectual delays. However, severe, untreated craniosynostosis could potentially affect brain growth.