Maxillary Sinus

1. Overview

The maxillary sinus is the largest of the four paired paranasal sinuses, situated within the maxilla (upper jaw bone). These air-filled cavities communicate with the nasal cavity and play important roles in respiration, voice resonance, and mucous drainage. The maxillary sinus is commonly involved in sinus infections and dental-related pathologies due to its proximity to the upper teeth.

2. Location

The maxillary sinuses are located:

• Within the maxillary bones, lateral to the nasal cavity

• Inferior to the orbits (eye sockets)

• Superior to the oral cavity, especially the roots of the upper molars and premolars

They are bordered:

• Medially: By the lateral wall of the nasal cavity

• Superiorly: By the orbital floor

• Inferiorly: By the alveolar process of the maxilla (tooth sockets)

3. Structure

The maxillary sinus has a pyramidal shape, with:

• Base: Medial wall adjacent to the nasal cavity

• Apex: Directed laterally toward the zygomatic process

Key anatomical features include:

• Ostium (opening): Located in the middle nasal meatus via the semilunar hiatus, allows mucus drainage

• Lining: Covered by pseudostratified ciliated columnar epithelium (respiratory epithelium)

• Blood supply: Branches of the facial, infraorbital, and greater palatine arteries

• Innervation: Via branches of the maxillary division of the trigeminal nerve (CN V2), including the infraorbital and superior alveolar nerves

4. Function

The maxillary sinus, like all paranasal sinuses, performs several functions:

• Air conditioning: Warms and humidifies inhaled air

• Mucous production: Produces mucus to trap debris and pathogens, which is moved into the nasal cavity via ciliary action

• Skull weight reduction: Their air-filled nature reduces the mass of the facial skeleton

• Resonance: Acts as a resonating chamber that contributes to vocal tone and timbre

5. Physiological Role(s)

In normal respiratory physiology, the maxillary sinus contributes to:

• Mucociliary clearance: Cilia move mucus upward toward the ostium for drainage into the nasal cavity

• Immune defense: Mucosal lining contains immune cells that respond to airborne pathogens

• Pressure equalization: Balances sinus and atmospheric pressure during changes in altitude or nasal airflow

6. Clinical Significance

Maxillary Sinusitis

One of the most common sinus infections. May be:

• Acute: Sudden onset, often viral or bacterial

• Chronic: Persistent symptoms due to poor drainage, allergies, or anatomical obstruction

Symptoms: Facial pain (especially over the cheeks), nasal congestion, purulent nasal discharge, pressure, and headache. May radiate to upper teeth.

Diagnosis: Clinical exam, nasal endoscopy, or CT scan

Treatment: Nasal decongestants, saline irrigation, antibiotics (if bacterial), and sometimes surgery (e.g., FESS)

Dental Involvement

The roots of the maxillary molars and premolars often protrude close to or into the sinus floor. Dental infections, extractions, or implants can lead to:

• Odontogenic sinusitis

• Oroantral fistula (communication between mouth and sinus)

Proper imaging and surgical planning are crucial in dental procedures in the posterior maxilla.

Maxillary Sinus Mucocele

A mucus-filled cyst caused by blockage of sinus drainage. Can lead to:

• Facial pressure

• Bone erosion

• Orbital symptoms if expansion occurs superiorly

Treatment is surgical drainage.

Maxillary Sinus Tumors

Both benign (e.g., inverted papilloma) and malignant (e.g., squamous cell carcinoma) tumors can arise in the sinus. Symptoms may include:

• Persistent nasal obstruction

• Unilateral facial swelling

• Epistaxis (nosebleeds)

Diagnosis involves endoscopy, imaging, and biopsy. Treatment is usually surgical with or without radiotherapy.

Iatrogenic Complications

Improper placement of dental implants or failure to recognize sinus proximity can lead to:

• Sinus perforation

• Implant migration into the sinus

Preoperative imaging (e.g., CBCT) is critical for sinus assessment.