Understanding the causes of a flat head
For many, a flat spot on the back of the head is a source of curiosity or concern. The reasons vary significantly depending on whether the flattening occurred during infancy or is being noticed in adulthood. The most common cause, especially in babies, is positional pressure, which is both treatable and preventable. However, other factors like genetics or more serious medical issues can also play a role.
Positional plagiocephaly and brachycephaly
The most frequent cause of a flat spot is external pressure on a baby's soft, malleable skull. This is a condition known as deformational plagiocephaly (when one side is flat) or brachycephaly (when the entire back of the head is flat). It became more prevalent after the "Back to Sleep" campaign recommended placing infants on their backs to reduce the risk of SIDS.
Factors contributing to positional flattening in infants:
- Prolonged back sleeping: While crucial for SIDS prevention, continuous back sleeping can put pressure on the same area of the skull.
- Torticollis: A tightening of neck muscles can cause a baby to favor turning their head to one side, leading to pressure and flattening on that area.
- Uterine constraint: In some cases, crowding in the womb can put pressure on a baby's head even before birth.
- Prematurity: Premature babies have softer skulls and often spend more time in a fixed position due to their fragility.
- Multiple births: Twins or triplets may have less space in the uterus, leading to external pressure on their developing heads.
Genetic factors
In some cases, the natural, inherited shape of an adult's skull can be a factor. Just as facial features are passed down, the general shape of the skull can be a family trait. If a person notices a flat spot that has been present since childhood and is not associated with other health issues, it may simply be a normal part of their genetic makeup.
Craniosynostosis: A more serious condition
While rare, a flattened head can be a sign of craniosynostosis, a birth defect where one or more of the fibrous joints (cranial sutures) in a baby's skull close prematurely. Unlike positional flattening, this condition restricts the growth of the skull, which can lead to abnormal head shapes and potentially increased pressure on the brain. This condition requires medical intervention, typically surgery.
Positional vs. Craniosynostosis:
| Feature | Positional Plagiocephaly/Brachycephaly | Craniosynostosis |
|---|---|---|
| Cause | External pressure on a soft, malleable skull. | Premature fusion of cranial sutures. |
| Symmetry | Asymmetrical (plagiocephaly) or symmetrical (brachycephaly). | Often results in an asymmetrical and ridged skull. |
| Growth | Skull growth is not restricted; the head simply molds to a flattened shape. | Skull growth is restricted at the fused suture, causing the head to grow disproportionately elsewhere. |
| Severity | Mild to moderate, often correctable with simple positioning changes. | More severe, requires surgical correction. |
| Associated Ridging | No ridging along sutures. | Palpable ridge may be present along the fused suture. |
What you can do about a flat head
If you are concerned about a flat spot, especially in an infant, there are several steps you can take. For positional issues, simple, non-invasive strategies are often effective.
- Repositioning: When your baby is awake, provide plenty of supervised tummy time. This strengthens neck muscles and gives the back of their head a break from pressure. Also, alternate the direction your baby faces in the crib or bassinet to encourage them to turn their head both ways.
- Holding and carrying: Minimize the amount of time your baby spends on their back in carriers, car seats, and swings. Hold your baby frequently to take pressure off their head.
- Helmet therapy: In more severe cases of plagiocephaly or brachycephaly that don't improve with repositioning, a doctor may recommend a corrective helmet. This helmet is custom-molded to gently reshape the baby's head as it grows.
- Addressing torticollis: If a tight neck muscle is the cause, physical therapy can be very effective in stretching and strengthening the neck to allow for full range of motion.
Long-term implications and adult concerns
For adults who notice a flat spot, the cause is almost certainly historical positional plagiocephaly. It's important to differentiate this cosmetic difference from a more serious condition. If the flattening occurred during infancy and has remained into adulthood, it is a permanent structural feature. However, it is primarily a cosmetic concern and does not typically affect brain development or cognitive function.
If you are an adult and are suddenly noticing a new or changing head shape, it's crucial to consult a doctor to rule out other medical issues. This is extremely rare, but could potentially signal an underlying condition that needs attention. For most adults, a historical flat spot is simply a part of their unique physical anatomy.
For additional information on head shape and cranial development, please consult reputable medical resources, such as the American Academy of Pediatrics website.
Conclusion
In summary, the reason why the back of a person's head may be flat is primarily due to either positional pressure during infancy or, in fewer cases, genetic disposition or craniosynostosis. The vast majority of cases in infants are benign and treatable with repositioning and time. While a flat spot in an adult is generally a permanent, harmless cosmetic feature, any new or changing head shape warrants a medical evaluation. By understanding the causes, individuals can make informed decisions and seek appropriate care, ensuring peace of mind about this common concern.
