What is a fontanelle?
Fontanelles are the soft, fibrous, membranous spaces between the cranial bones in an infant's skull. The human skull is not a single bone at birth, but a series of separate plates connected by flexible tissue known as sutures. At the intersections of these sutures are the larger gaps called fontanelles. The two most prominent are:
- Anterior fontanelle: Located on the top, front portion of the head, it is the larger and more commonly known soft spot.
- Posterior fontanelle: Situated at the back of the head, it is smaller and closes much earlier.
These soft spots serve two vital purposes during infancy. First, they allow the skull bones to compress and overlap during childbirth, enabling the baby to pass through the narrow birth canal. Second, they provide the necessary flexibility for the baby's brain to undergo rapid growth during the first couple of years of life.
The timeline of fontanelle closure
As a normal part of development, the infant's skull bones grow and fuse together through a process called ossification. The fontanelles close on a predictable schedule:
- The posterior fontanelle typically closes within the first two to three months after birth.
- The anterior fontanelle, the largest, usually closes between 7 and 19 months of age, with most closing by a child's second birthday.
By early adulthood, all sutures and fontanelles have typically fused, resulting in a solid, protective skull structure. A persistent or newly developed soft spot is therefore an unusual occurrence.
Why an adult might have a fontanelle
The presence of an open fontanelle or a soft spot on an adult skull is rare and always indicates an underlying health condition. Causes can be varied, but often point to issues with bone development, metabolism, or intracranial pressure. Potential causes include:
- Congenital disorders: Genetic conditions like cleidocranial dysplasia, which affects bone and tooth development, can prevent fontanelles from closing correctly. Osteogenesis imperfecta, which causes brittle bones, can also be a factor.
- Metabolic and endocrine issues: Conditions such as hypothyroidism can slow down bone growth and delay fontanelle closure. Similarly, severe nutritional deficiencies, particularly a lack of vitamin D, can lead to fontanelle issues.
- Hydrocephalus: The buildup of cerebrospinal fluid within the skull can increase intracranial pressure, preventing the skull bones from fusing properly or even causing re-opening of a soft spot in adults.
- Trauma: A head injury can damage the skull, leading to an indentation or a weak spot that feels like a fontanelle.
Diagnosis and treatment for an adult soft spot
If a soft spot is discovered on an adult's head, seeking medical attention is crucial. A healthcare provider will perform a physical examination and likely recommend imaging techniques for a definitive diagnosis. These tests may include:
- CT scan: Provides detailed, cross-sectional images of the skull to assess bone structure.
- MRI scan: Creates detailed images of the brain and surrounding tissues, which is essential for detecting issues related to intracranial pressure or fluid buildup.
Based on the diagnostic findings, treatment will address the root cause. This could range from managing an underlying metabolic condition to surgical intervention for issues like hydrocephalus. For cases stemming from previous trauma, management will focus on risk assessment and ongoing monitoring.
The dangers of an adult fontanelle
An open fontanelle in adulthood is not just a curiosity; it presents significant health risks. A primary concern is the reduced protection for the brain. Unlike the rigid, fused adult skull, an open fontanelle leaves a vulnerable area that is highly susceptible to injury from even minor impacts. This can increase the risk of serious brain injury, such as concussions or bleeding in the brain. Other long-term implications can include persistent headaches, localized pain, and other neurological symptoms.
Comparison: Infant vs. Adult Fontanelle
| Feature | Infant Fontanelle | Adult Soft Spot |
|---|---|---|
| Presence | Normal developmental feature | Medical anomaly, rare |
| Function | Facilitates birth and brain growth | Indicates underlying health issue or injury |
| Closure | Fuses into solid bone by age 2 | Remains open due to medical factors |
| Associated Risks | Typically low, if normal development | Significant risk of brain injury or underlying disease complications |
Conclusion: When to be concerned
While the sight of a pulsating soft spot on a newborn's head is normal and a sign of healthy development, the discovery of a fontanelle in an adult is a significant red flag. As detailed by reliable sources such as the MedlinePlus Medical Encyclopedia, fontanelles should close by the second year of life. The persistence or re-emergence of a soft spot warrants immediate medical consultation to identify the cause and mitigate any potential health risks. Never ignore a newly discovered soft spot on your head, even if it is painless, as it is your body's way of signaling that something is amiss.
Protecting your aging skull
Beyond fontanelles, maintaining overall skull and bone health is a crucial aspect of healthy aging. Ensuring adequate calcium and vitamin D intake, engaging in regular weight-bearing exercises, and avoiding head injuries can help prevent issues with bone density and integrity. For those with diagnosed conditions affecting bone health, adhering to a doctor's treatment plan is paramount to minimizing risks associated with compromised cranial protection.
