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Frontal Sinus

sinus frontalis

The frontal sinuses are paired air-filled cavities within the frontal bone above the orbits, separated by an often asymmetric bony septum. They drain through the frontonasal duct into the middle meatus of the nasal cavity via the ethmoidal infundibulum. They develop after age 2 and reach adult size by late adolescence. Their floor forms the roof of the orbit.

Region: Head & Skull

Clinical Relevance

Clinical Notes

Frontal sinusitis produces frontal headache, worse in the morning when drainage is dependent. Complications include mucocele (expansion into orbit or cranial fossa), osteomyelitis of the frontal bone (Pott puffy tumour), and intracranial spread. Frontal sinus trephination via a superomedial orbital incision provides emergency drainage. Endoscopic frontal recess surgery (FESS) opens the drainage pathway. Frontal sinus fractures require CT to assess posterior wall integrity and dural involvement.

Pathology

Common Injuries & Conditions

Frontal Sinus Mucocele

Obstruction of the frontonasal duct from trauma, polyps, or prior surgery causes a slowly expanding mucus-filled cyst within the frontal sinus that erodes the orbital roof or posterior wall, producing proptosis or intracranial extension managed by endoscopic or external sinus drainage and marsupialization.

Pott Puffy Tumour

Subperiosteal abscess of the frontal bone outer table from frontal sinusitis osteomyelitis produces a fluctuant forehead swelling (Pott puffy tumour) with intracranial extension risk, requiring emergent IV antibiotics, surgical drainage, and sinus debridement.