Frontal Sinus Aeration Timeline
Frontal sinuses begin pneumatization (aeration) around age 4-6 years, though they may not be visible on imaging until after age 6 years in most children. 1
Developmental Timeline
The frontal sinuses are the last of the paranasal sinuses to develop and show considerable variability in their appearance:
- Initial pneumatization begins around age 2-4 years 2, 3
- Frontal sinuses are not aerated before age 6 years in most children 4
- By age 4 years, pneumatization can be detected in some children 3
- Only 8% of children show frontal sinus pneumatization at 1-2 years of age 5
- By age 14-15 years, 97.8% of children demonstrate pneumatized frontal sinuses 5
- Maximal growth occurs during puberty, with continuous development until approximately age 20 years 3
Clinical Implications
When ordering imaging studies in young children, clinicians must recognize that absent or minimal frontal sinuses are developmentally normal and not pathologic. 6
Key Considerations:
- Frontal sinusitis cannot occur in children whose frontal sinuses have not yet pneumatized (typically those under 6 years of age) 6
- The absence of frontal sinuses on CT or MRI in infants and young children should be expected and not interpreted as abnormal 6
- Frontal sinusitis in older children (after pneumatization) carries significant risk for intracranial complications due to spread through valveless diploic veins 6
Comparison with Other Sinuses:
- Ethmoid and maxillary sinuses are present at birth, with maxillary sinuses showing significant pneumatization between birth and 12 months 1, 2
- Sphenoid sinuses begin development around age 3-4 years 1, 2
- All paranasal sinuses reach near-adult size by age 12-14 years 1
Common Pitfall
Do not order sinus imaging to evaluate for frontal sinusitis in children under 6 years of age, as the frontal sinuses are typically not yet developed and cannot be the source of infection. 6 This represents unnecessary radiation exposure and will not change clinical management.