Topics

Topic

design image
Septum of sphenoid sinus

The septum of the sphenoid sinus is the bony partition that divides the sphenoid sinus cavity into right and left chambers. Its configuration is highly variable, often deviating to one side and frequently attaching to critical structures such as the carotid canal or optic nerve canal. Because of these anatomical variations, the sphenoid sinus septum is of major surgical relevance, particularly in endoscopic transsphenoidal approaches to the pituitary gland.

The septum is formed by thin cortical bone and may be single, multiple, incomplete, or interdigitated, creating a complex sinus architecture. It contributes to sinus aeration patterns and serves as an internal bony landmark for ENT surgeons and skull base neurosurgeons.

Synonyms

  • Sphenoid septum

  • Inter-sphenoidal septum

  • Sellar sinus septum

Location and Structure

  • Location: Midline or near-midline within sphenoid sinus, dividing the cavity into separate compartments.

  • Composition: Thin cortical bone, occasionally with small trabeculae.

  • Variability:

    • Can be vertical, oblique, or curved

    • Complete or incomplete

    • Can attach eccentrically to the carotid canal, optic canal, or lateral sinus wall

  • Development: Pneumatization of the sphenoid bone guides septum formation during adolescence.

Relations

  • Superiorly: Sella turcica, pituitary gland

  • Inferiorly: Nasopharynx roof and sphenoid sinus floor

  • Laterally: Internal carotid artery canal, cavernous sinus, optic nerve canal

  • Anteriorly: Sphenoid sinus ostium

  • Posteriorly: Clivus

Attachments

  • Firmly attaches to the sphenoid sinus walls

  • Frequently deviates to one side, attaching asymmetrically to:

    • Carotid canal (very common)

    • Optic canal (less common)

    • Lateral sinus wall

  • Rarely attaches to inter-sphenoidal septations or accessory septa

Function

  • Divides the sphenoid sinus into compartments

  • Contributes to sinus aeration and drainage patterns

  • Provides internal orientation landmarks for endonasal and transsphenoidal surgery

  • Forms structural support within sinus cavity

Clinical Significance

  • ENT and neurosurgical relevance:

    • Septal attachment to the carotid canal increases risk of ICA injury during sinus surgery

    • Optic nerve canal attachment may complicate optic decompression procedures

  • Endoscopic pituitary surgery: Used as a landmark but highly variable

  • Sinus disease: Septum influences mucosal drainage pathways

  • Imaging importance: Essential in preoperative mapping of sphenoid sinus anatomy

MRI Appearance

T1-weighted images:

  • Septum appears as a thin low-signal (dark) structure within the sinus

  • Surrounded by bright fatty marrow if sinus wall marrow is present

  • Mucosa lining sinus appears thin and intermediate signal

  • Air-filled sinus cavity is dark

T2-weighted images:

  • Septum remains low signal, sharply delineated against bright sinus mucosa or fluid

  • Air remains dark

  • Superior borders show the bright pituitary gland/stalk contrast

STIR:

  • Septum appears dark, as cortical bone fully suppresses

  • Surrounding sinus mucosa demonstrates intermediate-to-bright signal depending on thickness

  • Offers high contrast with suppressed fat of skull base marrow

T2 3D (e.g., SPACE, CISS, DRIVE):

  • Septum is seen as a sharp, thin, dark linear bony structure

  • Air cavity is dark, while mucosa and fluid appear bright

  • Excellent delineation of:

    • Septal deviation

    • Septal attachment to carotid canal

    • Accessory septations

CT Appearance

Non-Contrast CT:

  • Best modality for evaluating septal anatomy

  • Septum appears as a thin high-density bony plate within the air-filled sinus

  • Clearly demonstrates:

    • Deviations

    • Complete vs incomplete septation

    • Attachments to ICA canal or optic canal

    • Bony thickness variations

  • Air cavity is black; mucosal thickening visible as soft tissue density

CT image

Septum of sphenoid sinus CT AXIAL

MRI image

Septum of sphenoid sinus MRI axial image-img-00000-00000