Management of Premature Anterior Fontanelle Closure in a 6-Month-Old
A 6-month-old with a closed anterior fontanelle requires urgent neuroimaging with brain MRI to rule out craniosynostosis and other intracranial pathologies, followed by appropriate specialist referrals based on findings.
Initial Evaluation
Clinical Assessment
- Measure head circumference and plot on growth chart
- Assess for signs of increased intracranial pressure:
- Bulging fontanelles (other fontanelles if still open)
- Irritability or lethargy
- Vomiting
- Setting sun sign
- Developmental delays
- Evaluate for dysmorphic features suggestive of syndromes
- Check for signs of metabolic disorders:
- Poor growth
- Hypotonia
- Developmental delays
Laboratory Testing
- Thyroid function tests (TSH, free T4)
- Calcium, phosphorus, alkaline phosphatase levels
- Vitamin D levels
- Consider genetic testing if dysmorphic features present
Imaging Studies
Brain MRI (Preferred Initial Study)
- American College of Radiology recommends brain MRI as the preferred initial imaging modality for evaluating premature fontanelle closure 1
- Advantages:
- No radiation exposure
- Superior visualization of brain parenchyma
- Ability to detect subtle abnormalities causing increased intracranial pressure
- Can identify craniosynostosis and associated brain abnormalities
CT Scan (Alternative)
- May be necessary if:
- MRI is not available
- Urgent evaluation is needed
- Patient cannot tolerate MRI
- Provides excellent bone detail to evaluate suture closure
Ultrasound (Limited Role)
- Not recommended as the sole imaging modality
- Has significant limitations:
- Limited sensitivity for small subdural hematomas
- Poor visualization of posterior fossa
- Inadequate detection of small extra-axial hemorrhages 1
Differential Diagnosis
Craniosynostosis
- Early closure of cranial sutures
- May present with abnormal head shape
- Not always associated with early fontanelle closure 2
- A comparative study showed that early anterior fontanelle closure does not necessarily imply craniosynostosis diagnosis, with a sensitivity of only 36.1% and specificity of 72% 2
Other Conditions Associated with Early Fontanelle Closure
- Microcephaly
- Hyperthyroidism
- Certain genetic syndromes
Conditions Associated with Delayed Fontanelle Closure (for comparison)
- Hypothyroidism
- Rickets
- Down syndrome
- Increased intracranial pressure
- Osteogenesis imperfecta 3
Management Algorithm
Immediate Neuroimaging
- Brain MRI as first-line imaging study 1
- If unavailable, high-resolution CT with 3D reconstruction
Specialist Referrals Based on Imaging Results:
If craniosynostosis is confirmed:
- Urgent neurosurgical consultation
- Ophthalmologic evaluation to assess for papilledema
- Consider surgical intervention if increased intracranial pressure or significant deformity
If hydrocephalus is present:
- Neurosurgical consultation for possible CSF diversion procedures 1
If normal imaging without craniosynostosis:
- Consider normal variant (though uncommon at 6 months)
- Schedule close follow-up monitoring of head circumference and development
- Repeat imaging in 3-6 months if concerns persist
If metabolic/endocrine abnormalities detected:
- Refer to pediatric endocrinologist for management
Follow-up Monitoring
- Regular head circumference measurements
- Developmental screening at each well-child visit
- Neurological examinations
- Follow-up imaging as recommended by specialists
Important Considerations
- Early anterior fontanelle closure is unusual at 6 months (median closure time is 13.8 months) 3
- While early closure doesn't always indicate craniosynostosis, the risk is significant enough to warrant thorough evaluation 2
- Developmental screening is essential as children with CHD and other conditions associated with early fontanelle closure may have higher rates of developmental delays 4
- The management approach must prioritize ruling out conditions that could lead to increased intracranial pressure, which can affect brain development and function