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Inferior sagittal sinus

The inferior sagittal sinus is a small but vital midline dural venous sinus located along the inferior edge of the falx cerebri in the brain. Running parallel and inferior to the larger superior sagittal sinus, it collects blood from the deep and medial surfaces of the cerebral hemispheres and drains posteriorly into the straight sinus. This venous channel plays a crucial role in the drainage of deep cerebral structures and is of key importance in neuroimaging, neurosurgery, and in the assessment of cerebral venous thrombosis.

Synonyms

  • Inferior longitudinal sinus

  • Sinus sagittalis inferior

  • Lower sagittal sinus

Function

  • Drains blood from the deep and medial aspects of both cerebral hemispheres

  • Collects venous blood primarily from the medial surfaces of the frontal and parietal lobes

  • Conveys blood posteriorly to the straight sinus, which then continues to the confluence of sinuses

  • Plays a role in overall cerebral venous outflow and regulation of intracranial pressure

MRI Appearance

  • T1-weighted images (T1):

    • The inferior sagittal sinus appears as a flow void (dark signal) due to rapid blood flow.

    • Well visualized as a thin, linear hypointense structure running along the inferior margin of the falx cerebri.

    • After contrast administration (Post-contrast T1), it demonstrates homogeneous enhancement, appearing hyperintense relative to non-contrast images.

  • T2-weighted images (T2):

    • Also presents as a flow void (hypointense linear signal).

    • The surrounding brain parenchyma is hyperintense, which helps in delineating the sinus.

  • 3D Phase Contrast (PC 3D) MRV:

    • Provides clear visualization of venous structures.

    • The inferior sagittal sinus appears as a slender, well-defined vascular channel.

    • Useful for mapping venous anatomy and evaluating patency or thrombosis.

  • Post-contrast T1-weighted imaging:

    • The sinus enhances brilliantly and linearly along the inferior falx cerebri.

    • Enhancement confirms the patency of the sinus and helps in differentiating from adjacent structures or thrombosed segments.

CT and CTV Appearance

  • Non-contrast CT:

    • The inferior sagittal sinus is typically not well visualized due to its small size and limited inherent contrast.

    • May appear as a subtle linear density along the inferior falx cerebri.

  • CT Venography (CTV):

    • CTV provides better visualization.

    • The sinus appears as a thin, contrast-filled linear structure at the base of the falx cerebri.

    • Helps in detecting sinus patency, filling defects (as seen in thrombosis), or anatomical variations.

MRI images

Inferior sagittal sinus MRI 3T sagittal image 1

MRI images

Inferior sagittal sinus MRI 3T PC 3D mip sagittal image

MRI images

Inferior sagittal sinus MRI 3T sagittal image

CT image

Inferior sagittal sinus CT