Paranasal Sinus Development

Developmental Timeline

The paranasal sinuses develop sequentially during childhood, with ethmoid and maxillary sinuses present at birth, maxillary sinuses beginning significant pneumatization between birth and 12 months, frontal sinuses appearing around age 4-6 years, and sphenoid sinuses beginning development around age 3-4 years, with all sinuses reaching near-adult size by age 12-14 years 1, 2
The maxillary sinus is the first to begin significant pneumatization between birth and 12 months of age 1, 2, 3
The floor of the maxillary sinus reaches the level of the nasal floor by approximately 12 years of age 1, 2
The ethmoid sinuses reach adult size at 12 to 14 years of age 1, 2, 3
The frontal and sphenoid sinuses develop later than maxillary and ethmoid sinuses 1, 2

Understanding developmental timelines is critical when interpreting imaging studies in children, as absence of certain sinuses may be normal depending on age 1, 2
Infections in the frontal and sphenoid sinuses have a greater propensity to cause intracranial complications due to their anatomic location 1, 2
The ostiomeatal complex is critical for drainage of maxillary, anterior ethmoid, and frontal sinuses, making this region most frequently involved in sinusitis 1, 2

The American College of Radiology recommends that clinicians recognize absent or minimal frontal sinuses as developmentally normal in young children, and not pathologic, when ordering imaging studies 4, 5, 6

Frontal sinusitis cannot occur in children whose frontal sinuses have not yet pneumatized, typically those under 6 years of age 7
The American College of Radiology suggests that the absence of frontal sinuses on CT or MRI in infants and young children should be expected and not interpreted as abnormal 4, 5, 6
Frontal sinusitis in older children, after pneumatization, carries significant risk for intracranial complications due to spread through valveless diploic veins 8, 9

The American College of Radiology advises against ordering 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 4, 5, 6