Anatomy of Maxillary and Sphenoid Sinuses
Maxillary Sinus Anatomy
The maxillary sinus is the largest of the paranasal sinuses, located within the body of the maxilla, and is intimately related to the roots of the posterior maxillary teeth, which explains the high frequency of odontogenic sinusitis. 1
Key Anatomical Features:
- Located in the body of the maxilla
- Pyramidal shape with its base forming the lateral nasal wall
- Drains into the middle meatus via the ostiomeatal complex
- Lined by respiratory epithelium with mucociliary clearance function
Important Relationships:
- Superior: Orbital floor
- Inferior: Alveolar process and posterior maxillary teeth roots
- Anterior: Anterior wall of maxilla (canine fossa)
- Posterior: Pterygomaxillary fissure and pterygopalatine fossa
- Medial: Lateral nasal wall
Microanatomical Variations:
The maxillary sinus shows significant individual variations that are crucial to understand for endoscopic sinus surgery to minimize tissue trauma and avoid complications, particularly to orbital structures 2. These variations include:
- Size and pneumatization patterns
- Position and size of the natural ostium
- Presence of accessory ostia
- Alveolar recess morphology
Sphenoid Sinus Anatomy
The sphenoid sinus is located within the body of the sphenoid bone and has complex relationships with critical neurovascular structures 3, 4.
Key Anatomical Features:
- Paired air cells within the sphenoid bone body
- Highly variable in size, shape, and degree of pneumatization
- Separated by an intersinus septum (often asymmetric)
- May extend into various recesses:
- Lateral recess (most common)
- Maxillary recess (less common)
Important Relationships:
- Superior: Pituitary gland in sella turcica, optic chiasm
- Lateral: Cavernous sinus, internal carotid artery, cranial nerves (III, IV, V1, V2, VI)
- Inferior: Nasopharynx, vidian canal
- Anterior: Posterior ethmoid cells
- Posterior: Clivus, brainstem
Maxillary Recess of Sphenoid Sinus:
A notable anatomical variant is the maxillary recess of the sphenoid sinus, which extends anteriorly, inferiorly, and laterally toward the maxillary sinus 5. This recess:
- Is separated from the maxillary sinus by a distinctive bony wall
- Can be mistaken for a Haller cell during surgery
- May contain important neurovascular structures like the sphenopalatine artery
- Requires careful CT evaluation prior to surgical intervention
Clinical Significance
Maxillary Sinus:
- Sinusitis Pathways:
- Rhinogenic: Starts with nasal inflammation → anterior ethmoid disease → obstruction of ostiomeatal unit → maxillary sinusitis 1
- Odontogenic: Direct spread from dental infections or iatrogenic causes (e.g., root canal perforations)
- Surgical Considerations:
- Prelacrimal approach for access
- Risk to infraorbital nerve during surgery
- Proximity to dental structures requires careful planning for implants and extractions
Sphenoid Sinus:
- Clinical Presentations: Often non-specific symptoms like headache, nasal discharge, or post-nasal drip 3
- Potential Complications:
- Mucocele formation
- Skull base involvement
- Cavernous sinus thrombosis
- Cranial neuropathies
- Surgical Approaches:
- Trans-sphenoidal approach to pituitary requires detailed understanding of sinus anatomy
- Critical to identify the relationship of sella turcica to sphenoidal sinuses 4
- CT imaging essential before intervention to identify individual variations
Imaging Evaluation:
- Multidetector CT: Primary modality for anatomical assessment and inflammatory conditions 3
- MRI: Better for soft tissue evaluation, tumors, and complications
- Pre-surgical Planning: Essential to evaluate individual variations, especially maxillary recess of sphenoid which could be mistaken for a Haller cell 5
Common Pitfalls and Caveats
- Failure to recognize the maxillary recess of the sphenoid sinus can lead to surgical complications if mistaken for a Haller cell 5
- Overlooking the intimate relationship between maxillary teeth roots and sinus floor can lead to odontogenic sinusitis
- Not appreciating the neurovascular relationships of the sphenoid sinus can result in serious complications including CSF leak, vascular injury, or cranial nerve damage
- Inadequate imaging evaluation before sinus surgery increases risk of complications