Cerebral Venous Sinus Thrombosis Cerebral Venous Sinus Thrombosis.pptx

Cerebral Venous Sinus Thrombosis

1. Cerebral Venous Sinus Thrombosis Barbara Simons, Geert Lycklama a Nijeholt and Robin Smithuis Radiology department of the Medical Centre Haaglanden in the Hague and the Rijnland hospital in Leiderdorp , the Netherlands

2. INTRODUCTION Cerebral venous thrombosis is an important cause of stroke especially in children and young adults. It is more common than previously thought and frequently missed on initial imaging. It is a difficult diagnosis because of its nonspecific clinical presentation and subtle imaging findings. In this article we will focus on: Findings on routine imaging that should make you think of unsuspected venous thrombosis. How to image patients in suspected venous thrombosis. Pitfalls.

3. Introduction When to think of venous thrombosis Dense clot sign Empty delta sign Absence of normal flow void on MR Venous infarction Imaging in suspected thrombosis CT-venography MR-venography DSA Pitfalls in CT Arachnoid Granulations Mimick of dense clot sign Pseudo empty delta sign Wrong bolus timing Pitfalls in MRI Hypoplastic transverse sinus Low signal intensity in thrombus Flow void on contrast-enhanced MR Chronic dural sinus thrombosis and related syndromes DAVF Thrombosis and increased CSF pressure Venous territories

4. Introduction Cerebral venous thrombosis is located in descending order in the following venous structures: Major dural sinuses: Superior sagittal sinus, transverse, straight and sigmoid sinuses. Cortical veins: Vein of Labbe, which drains the temporal lobe. Vein of Trolard , which is the largest cortical vein that drains into the superior sagittal sinus. Deep veins: Internal cerebral and thalamostriate veins. Cavernous sinus.

5. Introduction Venous territories On the left an illustration of the territories of the venous drainage. There is great variation in these territories and the illustration should be regarded as a rough guide.

6. Introduction Clinically patients with cerebral venous thrombosis present with variable symptoms ranging from headache to seizure and coma in severe cases. In neonates shock and dehydration is a common cause of venous thrombosis. In older children it is often local infection, such as mastoiditis, or coagulopathy. In adults, coagulopathies is the cause in 70% and infection is the cause in 10% of cases. In women, oral contraceptive use and pregnancy are strong risk factors.

7. Epidemiology Cerebral venous thrombosis is a rare condition accounting for approximately 0.5% of all cases of cerebrovascular disease worldwide  8 . Demographics of affected patients reflects underlying predisposing factors, which are identified in the majority of cases (87.5%) with many patients having more than one coexistent risk factors  2 :

8. Clinical presentation Unlike most other intracranial vascular conditions, the presentation can be highly variable and range from asymptomatic, seizure to coma and death, and may mimic a host of other conditions  1 .

9. Pathology Cerebral venous thrombosis pathogenesis remains poorly understood 5. There is an extensive list of known risk factors, already mentioned above. The lesion volume is related to the development of collateral veins in the affected venous segment. Venous hypertension from a poor outflow can lead to edema , cerebral venous infarction (~50% of cases 1) and even hemorrhage . Superior sagittal sinus or the dominant transverse sinus thrombosis can affect the arachnoid granulations absorption of cerebrospinal fluid, a consequent increase of cerebral swelling may occur 1

10. Radiographic features Unenhanced CT is usually the first imaging investigation performed given the nonspecific clinical presentation in these cases. CT Non-contrast CT, when not associated with venous hemorrhage or infarction can be a subtle finding, relying on hyperdensity of the sinus being identified  1,5 . Thrombus can appear as a  hyperdense vein  or sinus for the first 7-14 days; this is an accurate sign when present  6 .  With contrast administration, especially with a  CT venogram , a filling defect in a sinus is sought. When in the superior sagittal sinus it is referred to as the ' empty delta sign ’. CTV has a reported sensitivity of 95% compared to DSA as the gold standard  1 . CT perfusion Although not used routinely in clinical practice, whole brain CT perfusion may assist in establishing the diagnosis of CVT by detecting perfusion abnormalities that do not correspond with  arterial territories

11. MRI MRI is able to both visualize the clot as well as the sequelae. The clot acutely is isointense on T1 and hypointense on T2 (this can mimic a flow void), with subacute clot becoming hyperintense on T1. Cerebral edema can be identified even in the absence of neurological dysfunction or infarction  FLAIR a sulcal hyperintensity may reflect the presence of a localized subarachnoid hemorrhage T1 C+ may demonstrate focal pachymeningeal and leptomeningeal enhancement due to elevated blood pressure upstream of the thrombosis DWI/ADC the clot may demonstrate diffusion restriction on chronic stages

12. MRV W ill demonstrate a lack of flow. 2D  time of flight (TOF)  venography is routinely performed in suspected cases. Contrast MR venography is more sensitive in detecting dural venous sinus thrombosis than TOF venography. Hypoplastic dural sinuses and low flow areas remain a major problem with 2D TOF

13. Angiography (DSA) Although  digital subtraction angiography (DSA)  has historically been the  gold standard , the relative lack of experienced angiographic skills and invasive nature of the examination has led to a dramatic decline in its use as a primary mode of diagnosing cerebral venous thrombosis.

14. When to think of venous thrombosis Venous thrombosis has a nonspecific presentation and therefore it is important to recognize subtle imaging findings and indirect signs that may indicate the presence of thrombosis. Although these findings are often present on initial scans, they are frequently detected only in retrospect. Clinically patients with venous thrombosis often present with seizures, which is not a symptom in patients with an arterial infarction. On a routine non-enhanced MR or CT you should think of the possibility of venous thrombosis when you see: Direct signs of a thrombus Infarction in a non-arterial location, especially if it is bilateral and hemorrhagic Cortical or peripheral lobar hemorrhage Cortical edema

15. Dense clot sign Direct visualization of a clot in the cerebral veins on a non enhanced CT scan is known as the dense clot sign. It is seen in only one third of cases. Normally veins are slightly denser than brain tissue and in some cases it is difficult to say whether the vein is normal or too dense (see pitfalls). In these cases a contrast enhanced scan is necessary to solve this problem.

16. Dense clot sign (2) Visualization of a thrombosed cortical vein that is seen as a linear or cord-like density, is also known as the cord sign. Another term that is frequently used, is the dense vessel sign.

17. Dense clot sign (3) On the left images of a patient with a hemorrhagic infarction in the temporal lobe (red arrow). Notice the dense transverse sinus due to thrombosis (blue arrows).

18. Empty delta sign The empty delta sign is a finding that is seen on a contrast enhanced CT (CECT) and was first described in thrombosis of the superior sagittal sinus. The sign consists of a triangular area of enhancement with a relatively low-attenuating center , which is the thrombosed sinus. The likely explanation is enhancement of the rich dural venous collateral circulation surrounding the thrombosed sinus, producing the central region of low attenuation. In early thrombosis the empty delta sign may be absent and you will have to rely on non-visualization of the thrombosed vein on the CECT. The sign may be absent after two months due to recanalization within the thrombus.

19. Empty delta sign (2) On the left a case of thrombosis of the right transverse sinus and the left transverse and sigmoid sinus (arrows). There is enhancement surrounding the thrombosed hypoattenuating veins.

20. Absence of normal flow void on MR On spin-echo images patent cerebral veins usually will demonstrate low signal intensity due to flow void. Flow voids are best seen on T2-weighted and FLAIR images, but can sometimes also be seen on T1-weighted images. A thrombus will manifest as absence of flow void. Although this is not a completely reliable sign, it is often one of the first things, that make you think of the possibility of venous thrombosis. The next step has to be a contrast enhanced study. On the left a T2-weighted image with normal flow void in the right sigmoid sinus and jugular vein (blue arrow). On the left there is abnormal high signal as a result of thrombosis (red arrow).

21. Absence of normal flow void on MR (2) The images on the left show abnormal high signal on the T1-weighted images due to thrombosis. The thrombosis extends from the deep cerebral veins and straight sinus to the transverse and sigmoid sinus on the right. Notice the normal flow void in the left transverse sinus on the right lower image. Absence of normal flow void on MR-images can be very helpful in detecting venous thrombosis, but there are some pitfalls as we will discuss later. Slow flow can occur in veins and cause T1 hyperintensity.

22. Venous infarction The other sign that can help you in making the diagnosis of unsuspected venous thrombosis is venous infarction. Venous thrombosis leads to a high venous pressure which first results in vasogenic edema in the white matter of the affected area. When the proces continues it may lead to infarction and development of cytotoxic edema next to the vasogenic edema. This is unlike in an arterial infarction in which there is only cytotoxic edema and no vasogenic edema. Due to the high venous pressure hemorrhage is seen more frequently in venous infarction compared to arterial infarction. Since we are not that familiar with venous infarctions, we often think of them as infarctions in an atypical location or in a non-arterial distribution. However venous infarctions do have a typical distribution, as shown on the left.

23. Venous infarction Since many veins are midline structures, venous infarcts are often bilateral. This is seen in thrombosis of the superior sagittal sinus, straight sinus and the internal cerebral veins

24. Venous infarction (2) - Superior sagittal sinus thrombosis The most frequently thrombosed venous structure is the superior sagittal sinus. Infarction is seen in 75% of cases. The abnormalities are parasagittal and frequently bilateral. Hemorrhage is seen in 60% of the cases. On the left bilateral parasagittal edema and subte hemorrhage in a patient with thrombosis of the superior sagittal sinus.

25. Venous infarction (2) - Superior sagittal sinus thrombosis On the left reconstructed sagittal CT-images in a patient with bilateral parasagittal hemorrhage due to thrombosis of the superior sagittal sinus. The red arrow on the contrast enhanced image indicates the filling defect caused by the thrombus

26. Venous infarcts (3) - vein of Labbe Another typical venous infarction is due to thrombosis of the vein of Labbe. On the left images demonstrating hypodensity in the white matter and less pronounced in the gray matter of the left temporal lobe. There is a broad differential diagnosis including arterial infarction, infection, tumor etc. Notice that there is some linear density within the infarcted area. This is due to hemorrhage. In the differential diagnosis we also should include a venous infarct in the territory of the vein of Labbe. The subtle density in the area of the left transverse sinus (arrow) is the key to the diagnosis. This is a direct sign of thrombosis and the next step is a CECT, which confirmed the diagnosis (not shown).

27. Venous infarcts (3) - vein of Labbe On the left images of a patient with hemorrhage in the temporal lobe. When the hemorrhagic component of the infarction is large, it may look like any other intracerebral hematoma with surrounding vasogenic edema . The clue to the diagnosis in this case is seen on the contrast enhanced image, which nicely demonstrates the filling defect in the sigmoid sinus (blue arrow).

28. Venous infarcts (3) - vein of Labbe On the left a similar case on MR. There is a combination of vasogenic edema (red arrow), cytotoxic edema and hemorrhage (blue arrow). These findings and the location in the temporal lobe, should make you think of venous infarction due to thrombosis of the vein of Labbe. The next examination should be a contrast enhanced MR or CT to prove the diagnosis

29. Venous infarction (4) - Deep cerebral veins On the far left a FLAIR image demonstrating high signal in the left thalamus. When you look closely and you may have to enlarge the image to appreciate this, there is also high signal in the basal ganglia on the right. These bilateral findings should raise the suspicion of deep cerebral venous thrombosis. A sagittal CT reconstruction demonstrates a filling defect in the straight sinus and the vein of Galen (arrows).

30. Venous infarction (4) - Deep cerebral veins On the left a young patient with bilateral abnormalities in the region of the basal ganglia. Based on the imaging findings there is a broad differential including small vessel disease, demyelinisation , intoxication and metabolic disorders. Continue with the T1-weighted images in this patient.

31. Venous infarction (4) - Deep cerebral veins Notice the abnormal high signal in the internal cerebral veins and straight sinus on the T1-weighted images, where there should be a low signal due to flow void. This was unlike the low signal in other sinuses. The diagnosis is bilateral infarctions in the basal ganglia due to deep cerebral venous thrombosis

32. Venous infarction (5) - Edema In some cases of venous thrombosis the imaging findings can resolve completely. On the left a patient with a subcortical area of high signal intensity. The first impression was that this could be a low grade glioma. On a follow up scan the abnormalities had resolved completely. In retrospect a dense vessel sign was seen in one of the cortical veins and the diagnosis of venous thrombosis was made. The high signal intensity can be attributed to vasogenic edema due to the high venous pressure that resulted from the thrombosis.

33. Imaging in suspected thrombosis (CTV) CT-venography CT-venography is a simple and straight forward technique to demonstrate venous thrombosis. In the early stage there is non-enhancement of the thrombosed vein and in a later stage there is non-enhancement of the thrombus with surrounding enhancement known as empty delta sign, as discussed before. Unlike MR, CT-venography virtually has no pitfalls. The only thing that you don't want to do, is to scan too early, i.e. before the veins enhance or too late, i.e. when the contrast is gone. Some advocate to do a scan like a CT-arteriography and just add 5-10 seconds delay. To be on the safe side we advocate 45-50 seconds delay after the start of contrast injection. On the left some images of a CT-venography demonstrating thrombosis in many sinuses.

34. Imaging in suspected thrombosis (CTV) On the left images of a patient with an infarction in the area of the vein of Labbe. On the non-enhanced images you can appreciate the dense thrombus within the transverse sinus and the hemorrhage in the infarcted area. On the enhanced images a filling defect can be seen in the transverse sinus. You can scroll through the images.

35. MR-venography The MR-techniques that are used for the diagnosis of cerebral venous thrombosis are: Time-of-flight (TOF), phase-contrast angiography (PCA) and contrast-enhanced MR-venography: Time-of-Flight angiography is based on the phenomenon of flow-related enhancement of spins entering into an imaging slice. As a result of being unsaturated, these spins give more signal that surrounding saturated spins. Phase-contrast angiography uses the principle that spins in blood that is moving in the same direction as a magnetic field gradient develop a phase shift that is proportional to the velocity of the spins. This information can be used to determine the velocity of the spins. This image can be subtracted from the image, that is acquired without the velocity encoding gradients, to obtain an angiogram. Contrast-enhanced MR-venography uses the T1-shortening of Gadolinium. It is similar to contrast-enhanced CT-venography.

36. MR-venography On the left a lateral and oblique MIP image from a normal contrast-enhanced MR venography. Notice the prominent vein of Trolard (red arrow) and vein of Labbe (blue arrow). Every MR techniques has its own pitfalls as we will discuss in a moment. Contrast-enhanced MR venography has the disadvantage that you need to give contrast, but has less pitfalls.

37. DSA Angiography is only performed in severe cases, when an intervention is planned. On the left images of a patient with venous thrombosis, who was unconsious and did not respond to anticoagulant therapy. There is thrombosis of the superior sagittal sinus (red arrow), straight sinus (blue arrow) and transverse and sigmoid sinus (yellow arrow). Continue with the video of the thrombectomy.

38. Treatment and prognosis In ~50% of cases, cerebral venous thrombosis progresses to venous infarction  Unlike arterial infarcts, venous infarcts usually present after some days: <2 days of symptom onset: 30% 2-30 days: 50% >30 days: 20% The mainstay of hyperacute treatment is heparin, even in the setting of hemorrhagic venous infarction  Once the patient is stable, alternative enteral anticoagulation is commenced, including direct oral anticoagulants or warfarin  The optimal duration of anticoagulation is unknown, but generally at least 3 months.

39. Treatment and prognosis Surgical interventions are considered on a case-by-case basis. Interventional neuroradiologists/neurosurgeons can perform catheter-directed thrombolysis by using targeted thrombolytics in the affected sinuses. In patients who are critically unwell with pending brain herniation, observational data, in the absence of randomized control trials, suggests improved outcomes in selected patients managed with decompressive craniectomy. The natural history of cerebral venous thrombosis is highly variable, with some patients having minimal or no symptoms and an uneventful recovery (~65%), whereas others have a fulminant course culminating in extensive venous infarction and dependency or death (~20%). Not surprisingly, hemorrhagic venous infarcts and co-existing malignancy correlate with poor outcome  Deep cerebral venous thrombosis also has a negative impact on prognosis due to the usually bilateral involvement of the thalami

40. Complications Dural arteriovenous fistula , increased CSF pressure, and subarachnoid hemorrhage have been reported as possible complications after cerebral venous thrombosis.

41. Differential diagnosis The main differentials of cerebral vein thrombosis are: hypoplastic venous sinuses arachnoid granulations subdural hematoma

42. Chronic dural sinus thrombosis and related syndromes

43. DAVF On the left DSA images of a patient with a DAVF. Notice the direct communication between the branches of the external carotid artery and the transverse sinus (blue arrow). Continue with the T2-weighted images.

44. DAVF On the left T2-images during the follow up. In april 2008 there were no abnormalities. In january 2009 there are signs of intracranial hypertension like CSF surrounding the optic nerve and CSF within the stalk of the hypophysis.