CT Clues to Cerebral Venous Sinus Thrombosis.pptx

Cerebral Venous Sinus Thrombosis (CVST) refers to the formation of a blood clot in the brain's venous sinuses, which can disrupt normal blood flow and lead to neurological symptoms. CT scans can help identify signs of CVST, such as hyperdense thrombus, swelling, and hemorrhage. Early detection through CT imaging is crucial for effective treatment and preventing severe complications.

1. CT Clues to Cerebral Venous Sinus Thrombosis Dr MohammadMilad MollaGhanbari Radiologist Radiologist In the Name Of God

2. CONTENTS 01 Pathophysiology & CT Basics 02 Direct Signs on CT 03 Indirect Parenchymal Clues 04 Advanced CT Techniques 05 Diagnostic Algorithms 06 Pitfalls & Teaching Cases

3. Pathophysiology & CT Basics 01

4. PATHOPHYSIOLOGY & CT BASICS Why Sinuses Thrombose on CT Understanding the cascade from clot formation to parenchymal changes is key to recognizing early, subtle signs before classic findings appear. Clot Formation Predisposing conditions like infection, trauma, or hypercoagulable states initiate thrombus formation within the dural sinuses. Venous Hypertension Obstructed venous outflow leads to increased venous pressure , resulting in vasogenic edema and reduced perfusion. Parenchymal Changes Progressive ischemia and cytotoxic edema manifest as tissue density changes, hemorrhagic infarction, and mass effect on CT.

5. CT Protocols That Spot CVST Early Optimizing acquisition parameters is the prerequisite for reliable sign detection in all stages. Multislice CT Acquisition Utilize thin slices (<1mm) and a sharp reconstruction kernel Contrast-Enhanced CT Venography (CTV) Time the venous phase (typically 40-60s delay ) to ensure optimal sinus opacification. Dual-energy CT can reduce beam-hardening artifacts.

6. CTV & MIP Reconstruction Keys Advanced reconstructions significantly increase the conspicuity of thrombus, especially when partially occlusive. Maximum-Intensity-Projection (MIP) MIP images enhance the visibility of filling defects by displaying the voxel with the highest attenuation along a ray. This is invaluable for detecting subtle thrombus. Multiplanar Reconstructions (MPR) Reconstructing images in coronal and sagittal planes helps distinguish true thrombus from flow artifacts, particularly in the transverse and sigmoid sinuses.

7. Direct Signs on CT 02

8. Hyperdense Triangle & Cord Signs These direct signs on unenhanced CT are often the first clue, but require careful interpretation to avoid false positives. Hyperdense Triangle Sign Represents dense clot within a dural sinus (e.g., superior sagittal sinus). Look for attenuation values significantly higher than normal blood (>60-70 HU). Cord Sign A linear hyperdensity representing a thrombosed cortical vein. It is less common but highly specific when seen. a density score > 70 = perfectly predicted a positive (missing a fifth of the positive cases); cutoff point of 60 shows all positive cases (significant false positives)

9. The Empty Delta Sign A classic sign of CVST on contrast-enhanced CT, but it must be distinguished from normal variants and artifacts. True Positive Sign A triangular filling defect within an enhancing sinus, best seen on axial images. It represents thrombus surrounded by opacified blood. Pitfalls to Avoid Differentiate from arachnoid granulations, sinus hypoplasia, or partial-volume artifacts by examining contiguous slices and using multiplanar reformats.

10. The Empty Delta Sign A classic sign of CVST on contrast-enhanced CT, but it must be distinguished from normal variants and artifacts. (a) Transverse-sigmoid sinus passage; (b) posterior third of the superior sagittal sinus (SSS); (c) middle third of the SSS mean relative difference value lower than 10% represents absence of thrombosis

11. Indirect Parenchymal Clues 03

12. Venous Infarcts: Beyond Arterial Boundaries A non-arterial distribution of edema or hemorrhage is a critical indirect sign that should prompt immediate scrutiny of the venous system. Key Characteristics Multiple and bilateral lesions Subcortical white matter involvement Variable hemorrhagic conversion Crosses typical arterial boundaries Pathophysiology Delayed venous return leads to a combination of cytotoxic and vasogenic edema, visible as hypodensity on CT, which does not conform to major arterial territories.

13. Edema, Hemorrhage & Mass Effect The spectrum of parenchymal injury in CVST carries significant prognostic implications and often requires urgent intervention. Edema Early vasogenic edema is reversible . Progression to cytotoxic edema signifies irreversible ischemia and a poorer prognosis. Hemorrhage Hemorrhagic conversion is common. Petechial hemorrhage is frequent, but large hematomas can cause rapid deterioration and require surgical evaluation. Mass Effect Significant mass effect, midline shift, or uncal herniation are neurosurgical emergencies requiring immediate intervention to prevent death.

14. Diagnostic Algorithms 04

15. Stepwise CT Reading Checklist A systematic approach standardizes reports and minimizes missed cases in high-volume settings. 1 Non-Contrast CT Inspect sinus density for hyperdense triangle/cord signs. 2 Parenchyma Look for non-arterial edema or hemorrhage. 3 CTV Scrutinize for filling defects (empty delta sign). 4 Compare & Report Compare with prior imaging and assign a confidence level.

16. When CT is Inconclusive: Next Steps A clear pathway balances diagnostic certainty with resource stewardship and patient safety. Clinical Red Flags Progressive headache, papilledema, focal neurological deficits, or altered mental status in the setting of an equivocal CT scan are indications for further imaging . MRI/MRV The gold standard for diagnosis. Highly sensitive and specific, with no ionizing radiation. Digital Subtraction Angiography (DSA) Reserved for cases where endovascular treatment is planned or diagnosis remains uncertain after non-invasive imaging.

17. Pitfalls & Teaching Cases 06

18. Common Mimics & How to Avoid Them Avoiding false positives is critical to prevent unnecessary anticoagulation. Arachnoid Granulations Usually low density, well-defined, and in typical locations (lateral sinuses). Do not mistake for thrombus. Sinus Hypoplasia/Aplasia A common normal variant, often asymmetric. Check for a small, smooth lumen rather than a filling defect. High Hematocrit Can cause increased attenuation of blood. Correlate with lab values and look for a global, rather than focal, increase. Beam-Hardening Artifact From the skull base. Use dual-energy CT or review MPRs to confirm a true filling defect.

19. Top image shows unenhanced brain CT image with a thrombus with a density below the normal range in the left transverse sinus (a, arrows) that was not picked up as CVST by the readers. Note the similar density of CSF in the cisterna magna (a, arrowhead) to that shown on the subsequent contrast enhanced CT (b).

20. Deep cerebral venous thrombosis (DVT) in a 41-year-old man (patient 4) who presented with coma. A) Axial unenhanced CT shows an area of increased attenuation within the straight sinus and the internal cerebral veins associated with an area of low attenuation in both the basal ganglia

21. A 35-year-old woman with an SVT of the SSS and the RTS, who presented with headache and nausea

22. A 27-year-old woman in the control group, who initially presented with headache, but all other available imaging modalities showed no pathologic findings and clinical follow-up was uneventful.

23. HU: Hounsfield Unit, H:H ratio: Hounsfield Hematocrit ratio, VA: venoarterial