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Straight sinus

The straight sinus is a critical dural venous sinus located within the cranial cavity, playing a vital role in cerebral venous drainage. It forms at the junction of the falx cerebri and tentorium cerebelli, running posteriorly to join the confluence of sinuses. The straight sinus is responsible for draining blood from the deep structures of the brain, including the great cerebral vein (vein of Galen) and the inferior sagittal sinus, and directing it toward the transverse sinuses. Its evaluation is essential in the assessment of intracranial venous pathology, particularly in cases of thrombosis or anatomical variations.

Synonyms

  • Sinus rectus

  • Tentorial sinus

  • Straight dural sinus

Function

  • Drains blood from the deep venous system of the brain, primarily from the great cerebral vein (vein of Galen) and the inferior sagittal sinus.

  • Channels venous blood toward the confluence of sinuses (torcular Herophili), subsequently draining into the transverse sinuses.

  • Plays a role in maintaining cerebral venous outflow and intracranial pressure balance.

MRI Appearance

  • T2-Weighted Imaging

    • Appears as a flow void (black signal) due to rapidly flowing blood within the sinus.

    • Well-defined linear or tubular structure at the tentorial junction.

    • Loss of flow void may suggest thrombosis or slow flow.

  • T1-Weighted Imaging

    • Also demonstrates a flow void (hypointense signal) in normal conditions.

    • Thrombus may present as altered signal (isointense or hyperintense, depending on the stage).

  • 3D Phase Contrast (PC 3D) MRI

    • Provides clear visualization of venous flow within the straight sinus.

    • Highlights vascular anatomy and flow dynamics, allowing for detection of filling defects or venous anomalies.

  • Post-Contrast T1-Weighted Imaging

    • The straight sinus enhances brightly with contrast agent (gadolinium), confirming its patency.

    • Thrombus or obstruction appears as a non-enhancing filling defect.

CT Appearance

  • Non-Contrast CT

    • The straight sinus is seen as a hyperdense (brighter) linear structure in the midline, posterior cranial fossa.

    • Acute thrombosis may increase density (dense sinus sign).

  • CT Venography (CTV)

    • Provides detailed imaging of the sinus lumen.

    • The straight sinus enhances with contrast, outlining its course and patency.

    • Thrombosis is seen as a filling defect or lack of enhancement within the expected location of the sinus.

MRI images

Straight sinus MRI 3T coronal image

MRI images

Straight sinus MRI 3Taxial image