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Medial wall of maxillary sinus

The medial wall of the maxillary sinus forms the lateral wall of the nasal cavity and is a key anatomical interface between the maxillary sinus and the nasal passages. It contains the principal drainage pathway of the sinus and plays a central role in sinonasal ventilation and mucociliary clearance.

This wall is of major importance in functional endoscopic sinus surgery (FESS), dental–sinus pathology correlation, and radiologic evaluation of sinus disease.

Synonyms

  • Nasal wall of the maxillary sinus

  • Lateral nasal wall (sinus component)

Location

  • Forms the medial boundary of the maxillary sinus

  • Constitutes the lateral wall of the nasal cavity

  • Extends from the floor of the orbit superiorly to the alveolar process inferiorly

  • Located lateral to the inferior and middle nasal meatuses

  • Continuous posteriorly with the pterygopalatine region

Anatomical components

  • Thin bony wall formed mainly by the maxilla

  • Natural maxillary ostium:

    • Opens into the middle meatus

    • Located high on the medial wall

  • Accessory ostia (variable):

    • Usually posterior or inferior to the natural ostium

  • Mucosal lining:

    • Respiratory epithelium (Schneiderian membrane)

  • Related nasal structures:

    • Inferior turbinate (inferiorly)

    • Middle turbinate and uncinate process (superiorly)

Relations

Medially:

  • Nasal cavity

  • Inferior and middle nasal meatuses

Laterally:

  • Maxillary sinus cavity

Superiorly:

  • Ethmoid infundibulum

  • Osteomeatal complex

Inferiorly:

  • Alveolar process of the maxilla

  • Maxillary teeth roots (indirect relationship)

Anteriorly:

  • Anterior nasal cavity

Posteriorly:

  • Pterygopalatine fossa (via posterior wall continuity)

Structures related to the medial wall

  • Maxillary sinus ostium

  • Uncinate process

  • Ethmoid infundibulum

  • Inferior turbinate

  • Middle turbinate

Clinical significance

  • Sinus drainage: High ostium position predisposes to fluid retention

  • Osteomeatal complex obstruction: Common cause of maxillary sinusitis

  • Accessory ostia: May contribute to mucus recirculation

  • Endoscopic sinus surgery: Medial wall landmarks are critical for safe antrostomy

  • Dental–sinus disease spread: Inflammation may extend across thin bony partitions

  • Imaging pitfall: Normal mucosal folds may mimic pathology

X-ray appearance

Occipitomental (Waters) view:

  • Medial wall: Thin radiopaque margin forming sinus boundary

  • Sinus cavity: Radiolucent when aerated

  • Nasal cavity: Seen medial to the sinus

CT appearance

Non-contrast CT (coronal preferred):

  • Medial wall: Thin bony plate separating sinus from nasal cavity

  • Ostium: Small opening into the middle meatus

  • Accessory ostia: May be seen as additional defects

  • Osteomeatal complex: Best evaluated in this plane

Post-contrast CT:

  • Bony wall: No enhancement

  • Mucosa: Thin linear enhancement when present

3D CT VRT appearance

Volume-rendered technique (VRT):

  • Medial wall contour: Smooth, curved inner boundary of the sinus

  • Ostial region: Demonstrates relationship to middle meatus

  • Surgical planning: Useful for appreciating sinus–nasal cavity orientation

MRI appearance

T1-weighted images:

  • Bony medial wall: Low signal intensity

  • Sinus air: Signal void

  • Nasal mucosa: Intermediate signal

T2-weighted images:

  • Bony wall: Low signal

  • Air-filled sinus: Signal void

  • Mucosa: Intermediate-to-high signal

MRI image

MRI Medial wall of maxillary sinus anatomy image -img-00000-00000

X-Ray image

Medial wall of maxillary sinus