Is a nearly closed anterior fontanelle normal in a 21‑month‑old child who is otherwise healthy?

Nearly Closed Anterior Fontanelle at 21 Months: Normal Variant

A nearly closed anterior fontanelle at 21 months of age is within normal limits for an otherwise healthy child and requires no intervention beyond routine developmental surveillance. 1, 2

Normal Fontanelle Closure Timeline

The anterior fontanelle demonstrates wide variation in normal closure timing:

• Median closure age: 13.8 months (range extends well into the second year of life) 2
• Normal variation: Approximately 8% of healthy children still have an open fontanelle at 24 months of age 3
• At 21 months: A nearly closed or fully closed fontanelle falls well within the expected developmental range 2, 3

The fontanelle size progressively decreases after 6 months of age, with the most rapid closure occurring between 6-18 months 3.

Clinical Assessment Required

For this 21-month-old, focus your examination on specific findings that would indicate pathology rather than normal variation:

Essential measurements and observations:

• Head circumference: Plot on growth chart to confirm normal growth trajectory (not microcephaly or macrocephaly) 1, 4
• Head shape: Assess for cranial asymmetry, ridging along suture lines, or abnormal skull contours that suggest craniosynostosis 4
• Neurological examination: Check for signs of increased intracranial pressure including altered mental status, vomiting, lethargy, or bulging fontanelle (if still palpable) 1, 2
• Developmental milestones: Screen for age-appropriate motor, language, and cognitive development 1

When Imaging Is NOT Needed

No imaging is indicated for this child if:

• Head circumference follows a normal growth curve 1, 4
• Head shape is normal without cranial deformities 4
• Neurological examination is normal 1
• Development is age-appropriate 1

The diagnosis of craniosynostosis is strictly clinical and does not require routine radiographic imaging 4. Direct X-ray imaging is not indicated as a routine examination for fontanelle abnormalities 4.

When Further Evaluation IS Needed

Consider additional workup only if concerning features are present:

Indications for imaging:

• Abnormal head growth: Microcephaly (head circumference <2nd percentile) or crossing percentile lines downward 1, 4
• Abnormal head shape: Cranial asymmetry, ridging, or deformity suggesting suture fusion 4
• Neurological signs: Developmental delays, increased intracranial pressure signs 1

Imaging modality selection:

• First-line: Ultrasound examination (if fontanelle still partially open) is often sufficient for suspected suture anomalies 4, 5
• CT imaging: Reserved only for surgical planning in confirmed craniosynostosis, not for routine diagnosis 1, 4
• MRI: Consider only if concerns about brain development or other neurological symptoms exist 1

Common Pitfall to Avoid

Do not confuse early fontanelle closure with craniosynostosis. Early closure of the anterior fontanelle does not imply craniosynostosis diagnosis—a study found only 36% sensitivity and 59% positive predictive value for craniosynostosis when fontanelle closed before 6 months 6. At 21 months, closure is expected and normal 2, 3.

Management Plan for This Patient

Reassurance and routine monitoring:

• Confirm normal head circumference on growth chart 1, 4
• Document normal head shape and neurological examination 1
• Continue routine well-child developmental surveillance 1
• No imaging or specialist referral needed if examination is normal 1, 4

The key distinction is that premature fontanelle closure (before 6 months) warrants closer evaluation, while closure at 21 months represents the tail end of the normal distribution and requires no special intervention in a healthy child 2, 3.