Radiological imaging of cerebral venous thrombosis.

Dr/ ABD ALLAH NAZEER. MD.

ANATOMICAL REVIEWCEREBRAL VENOUS DRAINAGEThe cerebral venous system consists of a superficial and a deep system that drains into the venous sinus system and finally gets to the internal jugular veins.The veins are located on the surface of the cerebral hemispheres and not follow the arteries. SUPERFICIAL VENOUS SYSTEM:Drains the cerebral cortex and underlying white matter.External group:Superiors cerebral Veins are named for the lobe that they drain. Empty the superolateral side of the brain.Superficial middle cerebral vein: drains the lateral surface of the hemisphere.Superior anastomotic vein (Trolard) connects the SSS and Superficial middle cerebral vein.Internal Group: Collect blood from the inner side of the brain. Drain into the SSS.Inferior Group: Formed by the deep middle cerebral vein. It drains the lower surface of the hemisphere and the insula. It joins with the anterior cerebral veins and the striatum to form the basal vein (Rosenthal). 

DEEP VEIN SYSTEM: The deep system drains blood from the mass of brain tissue. Its formed by several veins draining into two main tributaries: Internal cerebral veins, Basal vein of Rosenthal The vein of Galen is formed by the union of internal cerebral vein and basal vein.The infratentorial veins drain superiorly into the vein of Galen. DURAL VENOUS SINUSES:Are enclosed in the leaves of the dura, they collect the blood from the brain veins. The superior sagittal sinus (SSS) runs from the anterior aspect of the falx cerebri to its termination at the confluence of the sinuses. It receives venous blood from the internal and external aspects of the hemispheres and middle meningeal veins.The inferior sagittal sinus (ISS) runs by the lower aspect of the falx cerebri. It receives tributaries from the inner surface of both hemispheres and the corpus callosum.The straight sinus (SS) is located at the junction between the falx cerebri and the tentorium cerebelli. It drains to the confluence of sinuses.The transverse sinus (TS) drains from the confluence of the sinuses and run laterally along the interior surface of the occipital bone to the base of the petrous pyramid where becomes the sigmoid sinus.The cavernous sinus is located on both sides of the sella turcica. Communicates with orbital venous plexus and with the venous plexus of the sphenopalatine and pterygomaxillary fossae.The petrosal sinuses; the superior petrosal sinus receives blood from the cavernous sinus and the inferior petrosal sinus runs from the cavernous sinus to the jugular foramen, where joins the sigmoid sinus to form the internal jugular vein.

Normal sinovenous anatomy. (a, b) Axial MIP CT image (a) and 3D volume-rendered image from CT venography (oblique anterosuperior view

Coronal, sagittal and axial 3DTOF MR images showing normal venous anatomy.

Volumetric reconstructions images from contrast- enhanced MRI venography.

Coronal and sagittal MIP images TOF MR venography, demonstrates the dural sinuses. Superior sagittal sinus (red), Inferior sagittal sinus (yellow), Straight sinus (green), Confluence of the sinuses (blue), Transverses sinuses (sky-blue),Sigmoid sinuses (purple), Internal jugular vein (pink).

IMAGING TECHNIQUEComputed Tomography:Diagnostic findings include the following:On noncontrast CT scan, the classic finding is the delta sign, which is observed as a dense triangle (from hyperdense thrombus) within the superior sagittal sinus. However, this is not specific, since high attenuation in the healthy non-thrombosed sinus can be observed occasionally and is common in neonates because of an elevated hematocrit. On contrast-enhanced CT scan, the reverse delta sign (i.e., empty triangle sign) can be observed in the superior sagittal sinus from enhancement of the dural leaves surrounding the comparatively less dense thrombosed sinus. The presence of both the delta and reverse delta signs increases the likelihood of the diagnosis. On CT brain scan, infarctions in a nonarterial distribution in the white matter and/or cortical white matter junction, often associated with hemorrhage, should suggest the possible diagnosis of venous thrombosis. Bilateral cerebral involvement can occur, including the superior cerebral white matter of the convexities from superior sagittal sinus thrombosis, or the basal ganglia and thalami from internal cerebral vein thrombosis in which the internal cerebral veins appear hyperdense in the noncontrast scan. Indirect CT signs include focal cerebral cortical ischemia with gyral enhancement, small ventricles compressed by cerebral edema, and intense tentorial enhancement. Occasionally, the transcerebral medullary cortical veins can be observed.

MRI in conjunction with magnetic resonance venography (MRV) is both sensitive and specific enough to provide the best noninvasive method of diagnosing cerebral venous thrombosis:The diagnosis usually can be made without intravenous contrast, although contrast enhancement can aid in confirming the diagnosis. A thrombus can be directly visualized within a vessel. Secondary venous infarctions and foci of hemorrhage can be seen with gradient-echo images. In acute venous thrombosis, loss of flow void on T1-weighted images occurs along with hypointensity on T2-weighted images, making the determination of sinus occlusion difficult. In the subacute phase, blood clot can result in loss of normal flow void on T1-weighted images and T1 hyperintensity; conversely, on T2-weighted images, blood clot can be of low signal intensity, thus mimicking flowing blood. In this instance, blood is in the intracellular methemoglobin stage.Restricted diffusion may or may not be seen in cerebral venous thrombosis and, when present, may occasionally be reversible.[22] Partially recanalized chronic venous sinus thrombosis has been described to demonstrate intense enhancement of the thrombosed segments following intravenous gadolinium-based contrast agents. A case report of restricted diffusion in the optic nerves bilaterally has been described in the setting of cavernous sinus thrombosis.

AngiographyPrior to the advent of MRI, the diagnosis of cerebral venous thrombosis (venous sinus thrombosis)was confirmed by contrast arteriography.Classic findings include the following:Filling defects from thrombus within the venous sinus Occlusion of a draining sinus Secondary indirect angiographic findings are as follows:Decreased focal venous circulation around a thrombosed venous sinus Visualization of collateral circulation Narrowing of arteries in the involved region Prolonged contrast blush in the brain parenchyma Tortuous vessels in the capillary and venous phases Collateral flow in dilated anastomotic vessels

IMAGING FINDINGSThe radiological findings are divided in:Indirect signs: edema, vascular congestion, infarction, subarachnoid hemorrhage. Direct signs: Direct visualization of the thrombus. Some of the main radiological findings are: Cord sign: Thrombus appears as a linear hyperdense area on unenhanced CT. Venous collateral flow: Gyral and tentorial enhancement that can be extended to the white matter due to a disruption of the blood- brain barrier. PARENCHYMAL DISORDERSThe thrombus may obstruct venous drainage with increase pressure leading to vasogenic edema due to venous congestion, cytotoxic edema by cellular damage, cortical hemorrhage with subcortical extension and finally venous infarction that does not follow an arterial vascular territory.

Cord sign. Axial unenhanced CT images shows areas of hyperattenuating suggestive of thrombosis in the ST (arrows).

Dense triangle sign. Axial unenhanced CT images shows hyperattenuating within the SSS consistent with thrombus.

Empty delta sign. Axial contrast- enhanced CT images shows a central region of low attenuation consistent with a thrombosis in the SSS

Superior sagittal sinus, straight sinus and right transverse thrombosis.

Thrombosis of the superior sagittal sinus.

Thrombosis of the left transverse sinus.

Thrombosis of the superficial cerebral veins.

Thrombosis of the superior sagittal sinus.

Empty delta sign on MRI. Axial and coronal contrast enhanced MR venography images showing filling defects (arrows) within the right TS (a) and SSS (b) surrounded by dural enhancement.

Acute thrombus with a severe headache for 5 days. (a, b) Axial T2-weighted MR image (a) and axial T1-weighted MR image (b) show a thrombus in the left sigmoid sinus (arrows). The signal in the thrombus, compared with that in the normal brain parenchyma, is hypointense in a and iso- to hyperintense in b. (c) Frontal MIP image from coronal TOF MR venography shows a lack of flow in the distal portion of the left transverse sinus and the sigmoid sinus (arrows).

Subacute thrombosis. (a,b,c) T1WI, T2WI and FLAIR WI showing hyperintense areas within the SSS (arrows in a,b) and within the ST (arrows in c). (d,e) Restricted diffusion and corresponding low signal on ADC map are seen. (f) Axial unenhanced CT image shows hyperattenuating within the SSS and in the internal cerebral veins (arrows).

Subacute thrombus of the superior sagittal sinus. (a, b) Axial T1-weighted (a) and axial T2-weighted (b) MR images show an area of abnormal increased signal intensity in the superior sagittal sinus (arrow). (c) Sagittal source image from contrast-enhanced MR venography shows filling defects (arrows) due to a thrombus.

Direct signs:(a) axial T1WI MR showing an hyperintense area in the SSS consistent with subacute thrombosis. (b) Coronal contras- enhanced MRI shows filling defects within the right TS (arrow).

Chronic thrombosis. (a) axial contrast- enhanced CT, (b) Coronal T2WI, (c,d,e) Contrast enhanced MR venography and (f) coronal TOF MR Venography shows filling defects in the right ST, the sigmoid sinus and the SSS with partial recanalization and increased collateral circulation consistent with chronic thrombosis.

Chronic thrombosis of the left transverse and sigmoid sinuses.

Acute Vs chronic thrombosis (a) T1WI shows an hyperintense area in the SSS,(b,c) DWI, restricted diffusion and corresponding low signal on ADC map consistent with acute thrombosis. (d) Axial contrast enhanced MR venography image showing filling defects in the rigth ST, (e,f)DWI without restricted diffusion in a patient with chronic thrombosis.

Parenchymal disorders associated with subacute thrombosis (a) Axial unenhanced CT image and (b) Axial T2WI shows intraparenchymal hematoma (arrow in a) associated with important vasogenic edema in the left temporal lobe (arrow in b), (c) susceptibility defects in the superficial veins of the left temporal lobe (arrow in c). Hyperintensity within the confluence of the sinuses consistent with subacute thrombosis (arrow in d).

(a) Axial contras enhanced MRI shows filling defects within the right sigmoid sinus and ST with parietoccipital venous infarction associated (arrow in b).

(a) Axial contrast enhanced MR venography image and (b) axial contrast enhanced CT shows hypoplasia of the left transverse sinus, note the asymmetry between the two sinus (arrows).

(a) Axial contrast enhanced MR venography image showing filling defects indicative of thrombus in the right TS (blue arrows) and arachnoid granulations in the left side (red arrows). (b) MIP image from contrast enhanced MRI shows round filling defects within the both ST consistent with arachnoid granulations.

Thrombosis of the straight sinus, vein of Galen, and internal cerebral veins. (a) Axial intermediate-weighted image shows extensive signal abnormalities within both thalami and extending into the caudate nuclei (arrows). (b) Sagittal two-dimensional phase-contrast MR venogram demonstrates a portion of the deep venous system with no signal (arrows), a finding consistent with occlusion.

Parenchymal disorders associated with subacute thrombosis (a) Axial unenhanced CT image and (b) Axial T2WI shows intraparenchymal hematoma (arrow in a) associated with important vasogenic edema in the left temporal lobe (arrow in b), (c) susceptibility defects in the superficial veins of the left temporal lobe (arrow in c). Hyperintensity within the confluence of the sinuses consistent with subacute thrombosis (arrow in d).

(a) Axial contras enhanced MRI shows filling defects within the right sigmoid sinus and ST with parietoccipital venous infarction associated (arrow in b).

Pseudotumor cerebri with elevated cerebrospinal fluid pressure documented at lumbar puncture. Oblique volume-rendered images from contrast-enhanced MR venography show a hypoplastic right transverse sinus (arrowhead in a) and prominent smooth-bordered stenosis in distal portions of both the right (arrows in a) and the left (arrow in b) transverse sinuses. The morphologic structure of the stenosis is suggestive of extraluminal compression.

Transverse sinus atresia. Oblique MIP image from coronal TOF MR venography shows the complete absence of the medial part of the left transverse sinus (arrows).

Anomalous location of the superior sagittal sinus bifurcation. (a) Anteroposterior MIP image from TOF MR venography shows a high bifurcation of the superior sagittal sinus (arrow). (b) On the axial contrast-enhanced CT image, the early bifurcation of the sinus produces a pseudo empty delta sign (arrow), mimicking sinus thrombosis.

Chronic dural sinus thrombosis and related syndromes.

Thank You.