What causes fontanelle in adults? Exploring the Medical Roots of an Anomalous Condition

While fontanelles are normal and expected in infants, an estimated 1 in 20,000 newborns is born with a condition that can result in fontanelles not closing properly. For adults, the presence of a soft spot is highly anomalous and a critical sign of underlying pathology, making an understanding of what causes fontanelle in adults a matter of serious medical concern.

Quick Summary

Fontanelles in adults are not a normal anatomical feature and are caused by underlying health problems, including genetic disorders like cleidocranial dysplasia, endocrine conditions such as hypothyroidism, or acquired issues like hydrocephalus, severe trauma, or nutritional deficiencies that disrupt bone formation.

Key Points

• Not a Normal Condition: An adult fontanelle is a medical anomaly, not a normal part of the aging process or skull structure.

• Sign of Pathology: The presence of a soft spot in an adult almost always indicates an underlying health issue, such as a congenital disorder, metabolic disease, or neurological condition.

• Genetic Causes: Rare inherited disorders like cleidocranial dysplasia and osteogenesis imperfecta are known causes of persistent open fontanelles.

• Endocrine & Metabolic Links: Issues like hypothyroidism and severe Vitamin D deficiency can hinder bone formation, leading to fontanelle persistence.

• Neurological Pressures: Conditions causing increased intracranial pressure, such as hydrocephalus, can prevent or reverse skull suture fusion.

• Trauma as a Factor: Severe head trauma can damage the skull and its healing capacity, resulting in a new or reopened soft spot.

• Immediate Medical Attention: A fontanelle in an adult warrants a prompt and thorough medical evaluation, including advanced imaging, to determine the cause.

Understanding Fontanelles: The Difference Between Infants and Adults

Fontanelles, or "soft spots," are fibrous membranes separating the cranial bones in an infant's skull. Their primary purpose is to facilitate passage through the birth canal and to allow for the rapid brain growth that occurs in early life. Typically, these fontanelles close and fuse completely as a child develops, with the posterior fontanelle closing around 2 to 3 months and the anterior fontanelle between 12 and 18 months.

In adults, the cranial sutures are fully fused, forming a rigid protective structure for the brain. The presence of an open or soft spot after this developmental stage is a clear indicator that something is medically amiss. It is crucial to distinguish this from the normal anatomical structures of infancy.

Genetic and Congenital Disorders

Several rare genetic and congenital conditions can prevent the normal closure of fontanelles. These disorders affect bone growth and development, leading to persistent gaps in the skull's protective armor.

• Cleidocranial Dysplasia (CCD): This genetic disorder affects the development of bones and teeth and is a well-known cause of abnormally large fontanelles that may remain open throughout a person's life. Individuals with CCD may also have underdeveloped or absent collarbones.
• Osteogenesis Imperfecta (Brittle Bone Disease): This inherited disorder affects collagen production, the protein that gives bones their strength. The result is fragile, brittle bones, which can cause delays in skull fusion and persistent soft spots.
• Achondroplasia and Down Syndrome: Certain chromosomal or developmental abnormalities can also be associated with delayed fontanelle closure. While most fontanelles close eventually, in some cases they may not, or the skull structure remains weak.

Endocrine and Metabolic Issues

Proper bone development relies on a delicate balance of hormones and nutrients. Disruptions in these areas can prevent the fontanelles from closing correctly during childhood, resulting in a persistent condition into adulthood.

• Congenital Hypothyroidism: An underactive thyroid gland from birth can slow down overall growth and development, including the ossification process of the skull. This is a common cause of delayed or incomplete fontanelle closure.
• Rickets: Severe and prolonged deficiency of Vitamin D and calcium can lead to softened and weakened bones. In children, this can delay the fusion of the fontanelles, and in rare cases, the effects may persist.

Neurological and Systemic Conditions

Conditions that increase pressure within the skull or affect the body's systems can also cause or mimic a persistent fontanelle in adults.

Hydrocephalus

Hydrocephalus, the buildup of excess cerebrospinal fluid within the brain, can create pressure that pushes against the skull bones. In infants, this causes a bulging fontanelle, but in adults, it can cause the re-opening or expansion of the cranial sutures, creating a soft area. This condition can result from:

1. Infections: Such as meningitis, which causes inflammation and fluid buildup.
2. Tumors or Cysts: Obstructions can block the normal flow of cerebrospinal fluid.
3. Hemorrhage: Bleeding in the brain can block fluid drainage channels.
4. Trauma: A severe head injury can disrupt the flow or absorption of cerebrospinal fluid.

Other Medical Conditions

A wide range of other medical issues can be linked to skull abnormalities:

• Infections: Chronic infections like meningitis or sepsis can inflame the membranes surrounding the brain, impacting intracranial pressure and potentially affecting the skull sutures.
• Cancer: Certain cancers, including leukemia, can affect bone density and cranial structures.
• Cardiovascular Issues: Conditions like congestive heart failure can affect fluid pressure throughout the body, including the head.

The Impact of Trauma and Injury

While most adult fontanelles are congenital, severe trauma to the head can also cause a soft spot or an area of bone loss. A powerful blow, a penetrating injury, or complicated surgical procedures involving the skull can damage the bone and prevent proper healing, leaving a vulnerable area. The skull's natural protective abilities are compromised in such cases, and medical intervention is necessary to address the damage and prevent further risk to the brain.

Medical Evaluation and Diagnosis

Given the serious nature of an adult fontanelle, a medical evaluation is crucial. A healthcare provider will perform a physical examination and may order advanced imaging, such as a CT scan or MRI, to visualize the underlying brain structure and skull integrity. These diagnostic tools are essential for determining the root cause of the fontanelle and creating an appropriate treatment plan.

Infant vs. Adult Fontanelle: A Comparison

Feature	Infant Fontanelle	Adult Fontanelle
Purpose	Facilitates birth and allows for brain growth.	Serves no natural purpose; indicates pathology.
Closure Time	Closes naturally by 18–24 months of age.	Should be closed; persistence is abnormal.
Associated Conditions	Bulging due to hydrocephalus; sunken due to dehydration.	May signal genetic, metabolic, or acquired issues.
Significance	A normal stage of development.	A medical red flag requiring prompt evaluation.
Vulnerability	Protected by a tough membrane, but still vulnerable.	Represents a persistent, unprotected area of the skull.

Conclusion: A Clear Sign of Underlying Concern

In summary, while a fontanelle is a normal part of infancy, its presence in an adult is a rare and significant medical finding. It is not a symptom of normal aging but rather a result of an underlying condition—whether genetic, metabolic, neurological, or traumatic. Individuals who discover a soft spot on their head should not delay in seeking professional medical advice for a proper diagnosis and treatment. Proper management of these conditions is essential for protecting neurological health and improving the quality of life. For further authoritative information, consult medical resources like the National Institutes of Health.

Frequently Asked Questions

Can a fontanelle reopen in an adult?

Yes, although it is extremely rare. While skull sutures are normally fused by adulthood, conditions like hydrocephalus or severe head trauma can cause increased intracranial pressure, which may force the sutures to separate or prevent bone from forming, causing a soft spot to reappear or persist.

What kind of doctor should I see for a soft spot on my head?

If you notice a soft spot on your head, you should consult with a primary care physician first. They can then refer you to a specialist, such as a neurologist, geneticist, or endocrinologist, for further testing and a definitive diagnosis.

Is a soft spot in an adult a sign of cancer?

While it is not a common symptom, certain types of cancer, such as leukemia, have been linked to changes in bone density and can affect the structure of the skull. A thorough medical evaluation is necessary to rule out or diagnose a cancer-related cause.

How is a fontanelle in an adult diagnosed?

Diagnosis typically involves a physical examination, medical history review, and advanced imaging techniques. Doctors may use CT scans or MRI scans to get detailed images of the skull and brain to identify the root cause of the condition.

Can a nutrient deficiency cause a fontanelle in adults?

Yes, a long-term and severe deficiency of key nutrients like Vitamin D and calcium, often linked to rickets in childhood, can lead to weakened bone density. This can cause delayed or incomplete skull fusion, potentially persisting into adulthood.

What are the risks of having an unclosed fontanelle?

An unclosed fontanelle leaves a vulnerable area in the skull, increasing the risk of serious head injuries and infections, such as meningitis. It can also be a symptom of conditions that affect neurological function, requiring careful management.

Do all genetic disorders that cause fontanelles have other symptoms?

Many genetic disorders that cause unclosed fontanelles, such as cleidocranial dysplasia, are syndromic and present with a range of other symptoms affecting the skeletal system, teeth, and more. A medical geneticist can help provide a comprehensive diagnosis.