Delayed Closure of the Anterior Fontanelle
Definition
Delayed closure of the anterior fontanelle is defined as persistence of the fontanelle beyond 24 months of age, with the normal range of closure being 4 to 26 months (median 13.8 months). 1, 2, 3
- The anterior fontanelle at birth averages 2.1 cm in size 3
- Normal closure occurs with significant variation, with median closure at 13.8 months but can extend to 26 months in healthy children 2, 3
- Closure beyond 24 months is considered delayed and warrants evaluation 1
Causes of Delayed Anterior Fontanelle Closure
Primary Pathological Causes
The most common disease-associated causes include hypothyroidism, Down syndrome, increased intracranial pressure, achondroplasia, and rickets. 1, 3
Endocrine Disorders
- Hypothyroidism is a leading cause of delayed fontanelle closure 1, 3
- Growth hormone therapy can cause abnormal head growth, particularly when fontanelles are open at therapy initiation 1
Genetic and Skeletal Disorders
- Down syndrome is frequently associated with delayed closure 1, 3
- Achondroplasia causes delayed fontanelle closure beyond 24 months 1, 3
- Rickets results in delayed closure due to impaired bone mineralization 1, 3
Increased Intracranial Pressure
- Elevated intracranial pressure prevents normal fontanelle closure 1, 2, 3
- This represents a serious condition requiring urgent evaluation 1
Important Clinical Consideration
It is critical to recognize that delayed fontanelle closure can be a normal variant in otherwise healthy children, representing a normal outlier beyond the accepted ranges. 2
- Once pathological conditions are ruled out through history, physical examination, and appropriate diagnostic testing, persistent open fontanelle may simply represent normal variation 2
- Historical population studies suggest delayed closure may have been more common in certain populations, though reasons remain unclear 4
Clinical Evaluation Approach
Initial Assessment
- Measure head circumference and plot on growth charts to assess for microcephaly or abnormal growth patterns 1
- Perform complete neurological examination assessing for signs of increased intracranial pressure 1
- Implement developmental surveillance to identify any delays 1
Diagnostic Testing
- Ultrasound examination is often sufficient for evaluating suspected anomalies of cranial sutures and anterior fontanelle 5
- CT imaging should be reserved for surgical planning in selected cases, not routine diagnosis 5
- MRI should be considered if concerns exist about brain development or neurological symptoms 5, 1