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Posterior intercavernous sinus

The posterior intercavernous sinus is a small but significant venous channel located within the sella turcica of the skull base. It serves as a communication pathway between the left and right cavernous sinuses, passing posterior to the pituitary gland. This venous sinus forms part of the circular sinus (circulus venosus of the hypophysis), which encircles the pituitary gland, facilitating venous drainage from the cavernous sinuses and other related venous structures. Though its size and prominence can be highly variable, understanding its appearance and characteristics is crucial in neuroimaging, as it may be mistaken for pathology if unrecognized.

Synonyms

  • Intercavernous sinus posterior

  • Posterior circular sinus

  • Posterior communicating sinus (less common)

  • Part of the circulus venosus of the hypophysis

Function

  • Provides venous communication between the left and right cavernous sinuses

  • Contributes to the circular venous ring around the pituitary gland (circular sinus)

  • Assists in venous drainage of the pituitary gland and central skull base

  • Equalizes venous pressure between both cavernous sinuses

  • Facilitates drainage into the superior and inferior petrosal sinuses

MRI Appearance

  • T1-Weighted Images

    • Appears as a flow void (signal loss), due to rapid blood flow

    • May be seen as a thin, curvilinear, low-signal structure posterior to the pituitary gland

    • If slow flow or thrombosis is present, it may appear hyperintense or isointense to brain tissue

  • T2-Weighted Images

    • Typically presents as a flow void (dark or hypointense) in the expected location

    • Surrounding CSF may provide contrast, making the sinus more evident

    • Hyperintensity may indicate slow flow or thrombosis

  • FLAIR

    • Usually not visible (flow void) due to rapid blood flow

    • If visible, may indicate pathology (e.g., thrombosis, slow flow)

  • Post-Contrast T1 (Gadolinium-enhanced)

    • Shows linear or curvilinear enhancement posterior to the pituitary gland

    • Enhances as a thin, well-defined structure if patent

    • Helps differentiate from non-enhancing structures or lesions

CT Appearance

  • Usually not directly visible on non-contrast CT due to its small size

  • May be inferred as a thin curvilinear density posterior to the pituitary if well opacified with contrast

  • Better appreciated on CT venography, where it enhances along with the cavernous sinus

  • Important to distinguish from pituitary or sellar pathology

MRI images

Posterior intercavernous sinus mri axial image

MRI images

Posterior intercavernous sinus mri sagittal image