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Medial wall of the maxillary sinus

The medial wall of the maxillary sinus forms the lateral wall of the nasal cavity and represents the most anatomically complex wall of the sinus. It separates the air-filled maxillary sinus from the nasal cavity and plays a crucial role in sinus ventilation and drainage.

This wall contains the maxillary sinus ostium, which drains into the middle meatus of the nasal cavity via the infundibulum and hiatus semilunaris, making it a key component of the osteomeatal complex. Structurally, the medial wall is thinner than the anterior and posterior walls and is composed mainly of bone from the maxilla, inferior turbinate, palatine bone, and ethmoid bone.

Synonyms

  • Nasal wall of the maxillary sinus

  • Lateral nasal wall (sinus component)

Location and Structure

  • Forms the interface between the maxillary sinus and nasal cavity

  • Composed of thin bony lamina covered by respiratory mucosa

  • Contains the maxillary ostium in its upper portion

  • Inferiorly related to the inferior nasal meatus and inferior turbinate

  • Superiorly related to the middle meatus, uncinate process, and ethmoid infundibulum

Relations

  • Medially: Nasal cavity

  • Laterally: Maxillary sinus cavity

  • Superiorly: Ethmoid infundibulum and middle meatus

  • Inferiorly: Inferior turbinate and inferior meatus

  • Anteriorly: Nasolacrimal duct (opens into inferior meatus)

  • Posteriorly: Palatine bone contribution to lateral nasal wall

Function

  • Separates nasal cavity from maxillary sinus

  • Facilitates mucociliary drainage through the maxillary ostium

  • Participates in air conditioning and humidification

  • Acts as a key anatomical component of the osteomeatal complex

  • Provides structural support for nasal cavity and sinus interface

MRI Appearance

T1-weighted images:

  • Bone of the medial wall: low signal (dark)

  • Maxillary sinus air: very low signal

  • Nasal cavity air: very low signal

  • Mucosa: thin, intermediate signal lining the wall

  • Adjacent fat planes (pterygopalatine and facial fat): bright

T2-weighted images:

  • Bone: low signal

  • Air-filled sinus and nasal cavity: signal void

  • Normal mucosa: thin, intermediate-to-slightly bright line

  • Inferior and middle turbinates: intermediate signal soft tissue

STIR:

  • Bone: dark signal

  • Normal mucosa: intermediate-to-dark signal

  • Turbinates and nasal soft tissues: intermediate signal

  • Fat signal suppressed, improving delineation of mucosal lining

T1 Fat-Saturated Post-Contrast:

  • Bone: no enhancement

  • Normal mucosa: thin, mild linear enhancement

  • Turbinates and nasal soft tissues: homogeneous enhancement

  • Clear delineation of medial wall contour and ostium region

CT Appearance

Non-Contrast CT:

  • Medial wall: thin, sharply defined bony plate

  • Excellent visualization of:

    • Maxillary ostium

    • Uncinate process

    • Inferior and middle turbinates

  • Nasal cavity and sinus air: low attenuation

  • Ideal modality for evaluating bony anatomy and drainage pathways

Post-Contrast CT:

  • Bone: no enhancement

  • Normal mucosa: subtle enhancement

  • Nasal soft tissues and turbinates: homogeneous enhancement

  • Helps delineate sinus–nasal cavity interface

X-Ray Appearance

  • Best evaluated on Waters (occipitomental) view

  • Medial wall seen as a thin vertical radiopaque line forming the medial boundary of the maxillary sinus

  • Nasal cavity appears as central radiolucent area

  • Inferior turbinate may be seen projecting into nasal cavity

CT image

Medial wall of the maxillary sinus CT anatomy labelled image-img-00000-00000

OPG image

Medial wall of the maxillary sinus