Understanding skull shape changes throughout life
Changes in a skull's shape can occur at any age, but the causes and implications differ significantly between infants and adults. In babies, the skull is soft and has open joints (sutures), making it susceptible to external molding. In contrast, an adult skull is rigid and requires more significant forces or underlying conditions to alter its form. Exploring these causes offers crucial insights into both common and rare health issues.
Causes of skull deformation in infants
For newborns and infants, several factors can influence the shape of their still-forming skulls. These are the most frequently observed causes and typically involve the manipulation of the soft, pliable cranial bones.
Positional plagiocephaly (flat head syndrome)
Since the American Academy of Pediatrics recommended placing infants on their backs to sleep to prevent SIDS, the incidence of positional plagiocephaly has increased. This condition occurs when constant gravitational forces on one part of a baby's head cause it to flatten. It is cosmetic and not known to cause developmental delays, but can be a cause of skull change. Other contributing factors include spending too much time in car seats, swings, or bouncers, which applies pressure to the back of the head.
Craniosynostosis: premature suture fusion
Craniosynostosis is a congenital condition where one or more of the fibrous sutures in a baby's skull fuse prematurely, which can cause abnormal skull growth and shape. Unlike positional plagiocephaly, which is caused by external pressure, craniosynostosis is a true medical condition. Early diagnosis is critical because untreated cases can potentially restrict brain growth and increase pressure within the skull.
Types of craniosynostosis:
- Sagittal: The most common type, causing a long, narrow skull (scaphocephaly).
- Coronal: Premature closure of a suture near the ear, leading to a flattened forehead on the affected side.
- Metopic: Fusion of the suture from the nose to the soft spot, resulting in a triangular forehead (trigonocephaly).
- Lambdoid: A rare type causing flattening at the back of the head.
Other infant causes
- Birth molding: The pressure exerted during passage through the birth canal can cause a baby's head to be temporarily misshapen. This typically resolves within a few weeks as the skull bones settle.
- Torticollis: Tight neck muscles can cause a baby to consistently tilt their head to one side, leading to positional plagiocephaly.
- Intrauterine constraint: Crowding in the womb, often in multiple pregnancies, can put pressure on the baby's skull and affect its shape before birth.
Causes of skull changes in adults
While the adult skull is much more rigid, certain conditions and events can cause its shape to alter over time. These changes are often indicative of an underlying medical issue that requires evaluation.
Trauma
Severe head injuries can lead to skull fractures, some of which can physically deform the skull. A depressed skull fracture, for instance, involves a portion of the bone being pushed inward, potentially compressing the brain. Even mild traumatic brain injuries can cause subtle structural changes in the skull.
Bone diseases
Several rare bone diseases can disrupt normal bone remodeling processes and lead to skull shape changes:
- Paget's disease of bone: This condition interferes with the body's ability to replace old bone tissue, resulting in weakened, misshapen, and enlarged bones, including the skull.
- Gorham's disease: A rare condition characterized by the replacement of bone tissue with fibrous tissue, which can lead to bone loss in the skull.
- Fibrous dysplasia: Benign tumor-like growths in the bone can cause thickening and expansion of the skull.
Cancerous conditions
Certain bone-destructive cancers, such as multiple myeloma, can cause visible depressions or irregularities in the skull.
Age-related changes
With age, some natural bone remodeling occurs. Research shows subtle yet significant changes in adult skull shape, particularly within the inner cranial vault, potentially influenced by loss of gray matter volume or other physiological factors.
Genetic and cultural factors
Genetic syndromes and past cultural practices also contribute to variations in skull shape.
Syndromic craniosynostosis
In some cases, craniosynostosis is part of a broader genetic syndrome, which often involves other facial and limb anomalies. These include:
- Apert syndrome: Characterized by coronal craniosynostosis and fused fingers and toes.
- Crouzon syndrome: Involves craniosynostosis, underdeveloped facial features, and bulging eyes.
- Pfeiffer syndrome: Features craniosynostosis with broad thumbs and toes.
Artificial cranial deformation
Historically, many cultures practiced intentional skull modification, particularly on infants, for aesthetic or social reasons. This involved applying pressure via binding or specialized devices to achieve an elongated or flattened shape. A 2022 review in Discover magazine discusses the history and potential health impacts of this practice.
Positional plagiocephaly vs. craniosynostosis
It's important to distinguish between the two primary causes of infant head shape abnormalities.
| Feature | Positional Plagiocephaly | Craniosynostosis |
|---|---|---|
| Cause | External pressure on the soft skull. | Premature fusion of one or more cranial sutures. |
| Suture Status | Sutures are open and pliable. | A bony ridge may be present along the prematurely fused suture. |
| Head Shape | Flattening on one side (often the back) or uniformly on the back. | Shape depends on which suture is fused, e.g., long and narrow (sagittal) or triangular (metopic). |
| Head Growth | Head growth is symmetrical, but pressure creates a flattened area. | Growth is restricted perpendicular to the fused suture but can compensate in other directions. |
| Treatment | Repositioning, more tummy time, and possibly helmet therapy. | Typically requires surgical intervention to reopen the fused suture. |
| Severity | Primarily cosmetic; does not affect brain growth in most cases. | Can restrict brain growth and increase intracranial pressure if multiple sutures are fused. |
Diagnosis and treatment overview
For both infants and adults, a medical professional should evaluate any significant or sudden change in skull shape. Pediatricians often monitor an infant's head shape during well-child visits. Diagnostic tools may include:
- Physical examination: Palpating the skull to check sutures and fontanelles.
- Imaging: X-rays or CT scans can confirm suture fusion in cases of suspected craniosynostosis.
- Genetic testing: May be needed to diagnose syndromic cases.
Treatment varies depending on the underlying cause. Positional plagiocephaly can often be managed conservatively with repositioning techniques and physical therapy, or with helmet therapy for moderate to severe cases. Craniosynostosis usually requires surgery, especially in infants, to allow for proper brain growth. Adult conditions like Paget's disease or tumors are treated based on their specific nature and severity.
Conclusion
The shape of the human skull, whether in a developing infant or a mature adult, can be influenced by a wide array of factors. While many infant shape changes are benign and easily treatable, others, such as craniosynostosis, require prompt medical attention. For adults, a change in skull shape can be a sign of an underlying bone disease, trauma, or other condition. Early recognition and medical evaluation are key to ensuring the best possible health outcomes.
Reference for further reading
Craniosynostosis (Boston Children's Hospital)
Seeking medical advice
If you notice a sudden or concerning change in your or your child's skull shape, it is important to seek medical advice for an accurate diagnosis and treatment plan.
