Frontal Sinus

1. Overview

The frontal sinus is one of the four paired paranasal sinuses, consisting of two air-filled cavities located within the frontal bone, just above the eyes. These sinuses are part of the upper respiratory tract and connect to the nasal cavity. The frontal sinuses contribute to air filtration, voice resonance, and skull lightening, and are lined by mucosa that participates in the mucociliary clearance system. Like other sinuses, they are variable in size and shape between individuals and even between the left and right sides.

2. Location

The frontal sinuses are located:

• Within the frontal bone, superior to the orbital cavities

• Deep to the forehead region, just above the medial ends of the eyebrows

• Anterior to the anterior cranial fossa and inferior to the frontal lobe of the brain

Each sinus typically drains via the frontonasal duct into the middle meatus of the nasal cavity through the infundibulum.

3. Structure

The frontal sinuses are:

• Paired but often asymmetrical; they may be unequal in size or even absent (aplasia) in some individuals

• Lined by respiratory mucosa (pseudostratified ciliated columnar epithelium with goblet cells)

• Separated by a bony septum which may be complete or incomplete

• Surrounded by thin bone, with the anterior wall (forehead) being thick and the posterior wall (facing the brain) being thin and vulnerable to erosion

4. Function

The frontal sinuses, like other paranasal sinuses, perform several important functions:

• Humidification and warming: Condition inhaled air before it reaches the lungs

• Mucus drainage: Help clear pathogens and debris via mucociliary clearance into the nasal cavity

• Lightening the skull: Reduce skull weight while maintaining structural integrity

• Voice resonance: Contribute to sound modulation and resonance during speech

5. Physiological Role(s)

The physiological contributions of the frontal sinus include:

• Mucosal immunity: Secretes mucus rich in immunoglobulins and antimicrobial peptides to protect against respiratory pathogens

• Pressure regulation: Balances intranasal and atmospheric pressure to maintain comfort during activities such as flying or diving

• Thermoregulation and insulation: Insulates sensitive brain structures from sudden temperature changes in inspired air

6. Clinical Significance

Frontal Sinusitis

Inflammation of the frontal sinus, often due to infection or allergy. Can be:

• Acute: Caused by viral or bacterial upper respiratory infections

• Chronic: Persistent inflammation due to unresolved infection, polyps, or structural blockage

Symptoms: Forehead pain or pressure, nasal discharge, headache, and fever. May worsen when leaning forward.

Complications of Sinusitis

Because of its proximity to the brain and orbits, untreated frontal sinusitis can lead to serious complications:

• Pott’s puffy tumor: Subperiosteal abscess due to osteomyelitis of the frontal bone

• Orbital cellulitis or abscess

• Meningitis or brain abscess

These conditions require urgent medical and sometimes surgical intervention.

Frontal Sinus Fracture

Often caused by blunt trauma to the forehead. May involve:

• Anterior wall: Cosmetic deformity

• Posterior wall: Risk of cerebrospinal fluid (CSF) leak and meningitis

Treatment varies from observation to surgical repair depending on severity.

Frontal Sinus Surgery (Frontal Sinusotomy)

Indicated in chronic sinusitis, mucocele, or tumor. Functional endoscopic sinus surgery (FESS) may be used to reopen or enlarge the frontal recess for better drainage.

Frontal Sinus Mucocele

A mucus-filled cyst caused by obstruction of the sinus outflow tract. It may expand, erode surrounding bone, and compress nearby structures, especially the orbit. Treatment is surgical drainage or marsupialization.