Radiologic Diagnosis of Cerebral Venous Thrombosis: Pictorial Review

^{1 1}Department of Radiology, State University of New York Upstate Medical University, 750 E Adams St., Syracuse, NY 13210.
² Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT.

Received May 31, 2007; accepted after revision June 11, 2007.

 
Address correspondence to C. S. Poon (poonc{at}upstate.edu).

Abstract

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

 
Objective

Cerebral venous thrombosis is often associated with nonspecific clinical complaints. In addition, the imaging findings are often subtle. Underdiagnosis or misdiagnosis of cerebral venous thrombosis can lead to severe consequences, including hemorrhagic infarction and death.

Conclusion

This article reviews the radiologic findings and diagnostic pitfalls of cerebral venous thrombosis. After completing this article, the readers should have an improved ability to diagnose cerebral venous thrombosis accurately, using the optimal imaging tools to achieve this goal.

Keywords: brain imaging • cerebral venous thrombosis • CT • MRI • neuroradiology

Introduction

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

 
Cerebral venous thrombosis (CVT) is often underdiagnosed because it is an uncommon disease, it is associated with a wide spectrum of etiologic factors, clinical presentation is often nonspecific, and the diagnostic imaging features can be subtle.

The correct diagnosis of CVT relies on neurologic imaging. Radiologists play a crucial role in patient care by providing early diagnosis through interpretation of imaging studies. Early diagnosis leads to prompt treatment that can be effective. Delayed diagnosis is associated with high morbidity and mortality.

The purpose of this article is to review the clinical presentation and basic pathophysiology of the disease; review the approach for radiologic investigation, including emerging technology such as CT venography; review the imaging features of CVT; and show common pitfalls associated with the radiologic evaluation of this diagnosis. We have included many cases to illustrate the radiologic features of CVT. Whenever possible, findings on different imaging techniques are correlated and compared.

Predisposing Factors

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The list of factors associated with CVT is too extensive to be memorized [1–7]. A more manageable approach is to understand that they may involve one or more of the following mechanisms: direct involvement of the dural sinuses (e.g., infection, trauma, neoplastic infiltration), possibly with damage to the vascular endothelium; venous stasis; hypercoagulable states; and increased blood viscosity.

The frequency of these etiologic factors depends on age. Often, the cause is multifactorial. In neonates, acute systemic illness, such as shock or dehydration, may be the cause. Frequent causes in older children include local infection, such as mastoiditis, and coagulopathy. In adults, intrinsic or acquired coagulopathies become the most important factors, contributing to as many as 70% of cases. Infection contributes to less than 10% of cases in adults [1, 3]. In women of childbearing age, oral contraceptive use and pregnancy are strong risk factors. CVT actually occurs more often in puerperium than during the pregnancy. Although pregnancy-related CVT occurs more often in older women, age per se is not a risk factor.

The pathogenesis of CVT is complex and remains poorly understood. In 20–35% of cases, the cause remains unknown; therefore, one should remain suspicious, even in the absence of known risk factors [1–3].

Clinical Presentation

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

 
The clinical presentation of CVT is often nonspecific [1–6] (Table 1). Common presentation includes headache, focal neurologic deficits, seizures, and altered consciousness. A syndrome of intracranial hypertension (headache and papilledema) accounted for 40% of cases in a series, so CVT needs to be excluded in patients considered for the diagnosis of benign intracranial hypertension [1]. Although subarachnoid hemorrhage is a rare presentation of CVT, cases have also been reported [1, 8]. There is also a wide distribution in the mode of onset of symptoms, with approximately 28% acute (< 48 hours), 42% subacute (between 48 hours and 30 days), and 30% chronic (> 30 days) [1]. The teaching point is that CVT may have an atypical presentation or even an absence of clinical symptoms. The evaluation for evidence of CVT should be included in the diagnostic checklist in every neuroradiologic case.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —5-year-old boy with severe headache and eye pain. Thrombosis was found in right lateral sinus (arrows). Unenhanced CT images show thrombosis as hyperdensity (dense clot sign).

View larger version (120K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —5-year-old boy with severe headache and eye pain. Thrombosis was found in right lateral sinus (arrows). Unenhanced CT images show thrombosis as hyperdensity (dense clot sign).

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C —5-year-old boy with severe headache and eye pain. Thrombosis was found in right lateral sinus (arrows). Enhanced CT images show same structure as filling defect with enhancing rim (empty delta sign).

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D —5-year-old boy with severe headache and eye pain. Thrombosis was found in right lateral sinus (arrows). Enhanced CT images show same structure as filling defect with enhancing rim (empty delta sign).

View larger version (116K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —Cord sign in cortical venous thrombosis in a young woman. Unenhanced CT scans show dense cortical veins (white arrows,A), an uncommon direct sign of cerebral venous thrombosis (CVT) known as cord sign. Note also indirect signs of CVT, including subcortical hemorrhagic infarction (black arrows), diffuse brain swelling, and small ventricular size.

View larger version (139K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —Cord sign in cortical venous thrombosis in a young woman. Unenhanced CT scans show dense cortical veins (white arrows,A), an uncommon direct sign of cerebral venous thrombosis (CVT) known as cord sign. Note also indirect signs of CVT, including subcortical hemorrhagic infarction (black arrows), diffuse brain swelling, and small ventricular size.

View larger version (102K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). Unenhanced CT scans show dense thrombosis. Note nonhemorrhagic infarction in basal ganglia, thalami, and internal capsules, which is typically seen in deep cerebral venous thrombosis.

View larger version (100K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). Unenhanced CT scans show dense thrombosis. Note nonhemorrhagic infarction in basal ganglia, thalami, and internal capsules, which is typically seen in deep cerebral venous thrombosis.

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3C —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). Axial T2-weighted MR image shows replacement of signal void by thrombus (arrow) in superior sagittal sinus. Veins at internal capsules are engorged.

View larger version (135K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3D —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). Sagittal contrast-enhanced T1-weighted image (D) shows filling defects in sagittal and straight sinuses, correlating with absence of flow on 2D phase contrast MR venography (E).

View larger version (164K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3E —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). Sagittal contrast-enhanced T1-weighted image (D) shows filling defects in sagittal and straight sinuses, correlating with absence of flow on 2D phase contrast MR venography (E).

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3F —38-year-old woman with history of pseudotumor cerebri who presented with headache and decreased consciousness. Diagnosis was thrombosis of superior sagittal sinus, straight sinus, and internal cerebral veins. (Long white arrows indicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosenthal's veins). After catheter-directed thrombolysis, flow was partially reestablished.

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

Unenhanced CT
Direct signs of CVT are uncommon and are seen in only one third of cases. Direct visualization of thrombosis in dural sinus may give a "dense clot sign" (Fig. 1A, 1B, 1C, 1D). The cord sign represents direct visualization of a thrombosed cortical vein that is seen as linear hyperdensity (Fig. 2A, 2B).

More often, unenhanced CT shows only the indirect signs of CVT. These are often nonspecific and may include diffuse brain edema, leading to hypodensity of the brain (seen in 20–50% of cases) or decreased ventricular size. In young patients, the pathologic decrease in ventricular size may be difficult to differentiate from the normally small ventricles commonly seen in young patients.

Venous infarction is the most specific indirect sign on unenhanced CT images. An infarction not conforming to a major arterial vascular territory, such as the presence of multiple isolated lesions, involvement of a subcortical region with sparing of the cortex, and extension over more than one arterial distribution, is highly suspicious for a venous cause. The infarction may be hemorrhagic (Fig. 2A, 2B) or nonhemorrhagic (Fig. 3A). The location of the infarction with respect to the expected course of venous drainage may give a clue to the venous structure involved. Thrombosis in the sagittal sinus often leads to impaired venous drainage and, therefore, parenchymal change in the parasagittal region. Thrombosis in Labbé's vein should lead to infarction in the temporal lobe. Bilateral or unilateral infarction in the thalami, basal ganglia, and internal capsule is typically seen in deep venous thrombosis (Fig. 3A, 3B, 3C, 3D, 3E, 3F).

View larger version (124K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. Axial source images from CT venography. Thrombus in IJV (asterisk, A) and sigmoid sinus (black arrow,B) is clearly shown as filling defect. Note collateral veins (white arrow, A) arising from right IJV.

View larger version (127K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. Axial source images from CT venography. Thrombus in IJV (asterisk, A) and sigmoid sinus (black arrow,B) is clearly shown as filling defect. Note collateral veins (white arrow, A) arising from right IJV.

View larger version (110K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. Sagittal planar reconstruction of CT venography shows thrombus extending from right IJV (asterisk) into sigmoid sinus (arrow), correlating well with findings on conventional venography (E).

View larger version (160K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4D —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. T1-weighted MR image shows sigmoid sinus thrombosis (arrow) as seen on CT (B).

View larger version (114K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4E —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. Venogram (E) shows thrombus as filling defects. Note collateral veins at region of right IJVs, also seen in A. Venogram after suction thrombectomy (F) shows improved patency in right IJV and lateral sinus. Asterisk, right internal jugular vein; solid arrow, sigmoid sinus; open arrow, torcular Herophili.

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4F —16-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sigmoid sinus that was suspicious for venous thrombosis. Findings were confirmed on CT venography, MRI, and conventional venography. Venogram (E) shows thrombus as filling defects. Note collateral veins at region of right IJVs, also seen in A. Venogram after suction thrombectomy (F) shows improved patency in right IJV and lateral sinus. Asterisk, right internal jugular vein; solid arrow, sigmoid sinus; open arrow, torcular Herophili.

Indirect evidence of CVT may be seen as contrast enhancement of the falx and tentorium secondary to venous stasis and hyperemia of the dura mater, which is seen in approximately 20% of cases.

One should be aware that in 10–30% of cases of CVT, the findings on either unenhanced or contrast-enhanced CT are negative. Therefore, in highly suspicious cases, further evaluation with CT venography, or MRI with MR venography, is warranted.

CT Venography
A more recent tool that can be used to evaluate CVT is CT venography [10–12]. CT venography allows direct visualization of thrombus as filling defects (Fig. 4A, 4B, 4C, 4D, 4E, 4F).

View larger version (89K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —4-day-old neonatal boy after idiopathic cardiac arrest. Axial unenhanced CT scans show normal, hyperdense blood commonly seen in neonates and infants.

View larger version (88K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B —4-day-old neonatal boy after idiopathic cardiac arrest. Axial unenhanced CT scans show normal, hyperdense blood commonly seen in neonates and infants.

View larger version (100K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C —4-day-old neonatal boy after idiopathic cardiac arrest. T1-(C) and T2-weighted (D) MR images show normal findings.

View larger version (106K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5D —4-day-old neonatal boy after idiopathic cardiac arrest. T1-(C) and T2-weighted (D) MR images show normal findings.

View larger version (102K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A —Middle-aged woman (exact age unknown) with history of multiple myeloma. Axial unenhanced CT images show subdural hemorrhage at right cerebellar convexity that mimics thrombosis of right transverse sinus.

View larger version (79K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B —Middle-aged woman (exact age unknown) with history of multiple myeloma. Axial unenhanced CT images show subdural hemorrhage at right cerebellar convexity that mimics thrombosis of right transverse sinus.

View larger version (155K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6C —Middle-aged woman (exact age unknown) with history of multiple myeloma. Axial FLAIR image (C), coronal FLAIR image (D), and unenhanced CT scan (E) at location adjacent to B show similar finding of subdural hemorrhage (white arrow, E) medial to right transverse sinus (black arrow, E).

View larger version (155K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6D —Middle-aged woman (exact age unknown) with history of multiple myeloma. Axial FLAIR image (C), coronal FLAIR image (D), and unenhanced CT scan (E) at location adjacent to B show similar finding of subdural hemorrhage (white arrow, E) medial to right transverse sinus (black arrow, E).

View larger version (84K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6E —Middle-aged woman (exact age unknown) with history of multiple myeloma. Axial FLAIR image (C), coronal FLAIR image (D), and unenhanced CT scan (E) at location adjacent to B show similar finding of subdural hemorrhage (white arrow, E) medial to right transverse sinus (black arrow, E).

View larger version (130K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6F —Middle-aged woman (exact age unknown) with history of multiple myeloma. Contrast-enhanced MR venogram shows patent dural venous sinuses. Right transverse sinus (arrows) is smaller and slightly irregular compared with left, possibly secondary to mass effect from adjacent subdural hematoma.

Conventional MRI sequences often provide sufficient information to raise the suspicion or to make a diagnosis of CVT. The diagnosis can then be further confirmed on MR venography or CT venography.

MR Venography
MR venography may be performed without the use of a contrast agent using the time-of-flight (TOF) technique or the phase contrast technique. Because these techniques use MR flow phenomena for contrast generation, they are subject to flow-related image artifacts.

Similar to CT venography, contrast-enhanced MR venography takes advantage of luminal filling by contrast material rather than relying on the MR flow phenomena as in TOF or phase contrast MR venography. Therefore, contrast-enhanced MR venography is less likely to be affected by complex flow. Recently, gadolinium-enhanced MR venography has been shown to be superior to TOF MR venography [13, 14] and may offer the best evaluation using MRI. The various MR venography techniques are summarized in Table 2.

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7A —7-year-old girl with closed head injury. Unenhanced CT scans on first day show subdural hemorrhage along tentorium cerebelli and skull fracture. Subtle density is seen in right lateral sinus (arrows,B and C) that was not well appreciated initially.

View larger version (134K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7B —7-year-old girl with closed head injury. Unenhanced CT scans on first day show subdural hemorrhage along tentorium cerebelli and skull fracture. Subtle density is seen in right lateral sinus (arrows,B and C) that was not well appreciated initially.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7C —7-year-old girl with closed head injury. Unenhanced CT scans on first day show subdural hemorrhage along tentorium cerebelli and skull fracture. Subtle density is seen in right lateral sinus (arrows,B and C) that was not well appreciated initially.

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7D —7-year-old girl with closed head injury. On next day, repeat CT scan shows dense thrombus in right lateral sinus (arrows) mimicking subdural hematoma (compare E with A).

View larger version (124K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7E —7-year-old girl with closed head injury. On next day, repeat CT scan shows dense thrombus in right lateral sinus (arrows) mimicking subdural hematoma (compare E with A).

View larger version (155K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7F —7-year-old girl with closed head injury. On sagittal T1-weighted MR images, normal flow void is seen in left lateral sinus (arrow, F), but note isodense thrombus on right (arrow, G).

View larger version (154K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7G —7-year-old girl with closed head injury. On sagittal T1-weighted MR images, normal flow void is seen in left lateral sinus (arrow, F), but note isodense thrombus on right (arrow, G).

CT venography has been shown to be superior to traditional MR venography techniques based on 2D TOF or phase contrast techniques [10]. However, a direct comparison between CT venography and contrast-enhanced MR venography is not yet available. These two techniques probably provide comparable performance, and preference will be dictated by the experience and resources of the individual institutions.

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8A —4-month-old girl with seizure. Unenhanced CT scans show subdural hemorrhage along falx and tentorium cerebelli, simulating sagittal and transverse sinus thrombosis. Note pseudo empty delta sign (arrow, A). Empty delta sign of cerebral venous thrombosis is applicable only on contrast-enhanced CT. Hyperdensity along posterior parietal convexity simulates transverse sinus thrombosis (black arrow, B). Extension of hyperdensity beyond expected location of transverse sinus suggests this is actually subdural hematoma (white arrow, B) [8].

View larger version (149K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8B —4-month-old girl with seizure. Unenhanced CT scans show subdural hemorrhage along falx and tentorium cerebelli, simulating sagittal and transverse sinus thrombosis. Note pseudo empty delta sign (arrow, A). Empty delta sign of cerebral venous thrombosis is applicable only on contrast-enhanced CT. Hyperdensity along posterior parietal convexity simulates transverse sinus thrombosis (black arrow, B). Extension of hyperdensity beyond expected location of transverse sinus suggests this is actually subdural hematoma (white arrow, B) [8].

View larger version (141K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9A —29-year-old woman woman with headache. Contrast-enhanced T1-weighted image (A), source image of 2D time-of-flight (TOF) MR venography (B), and maximum-intensity-projection of 2D TOF MR venography image (C) show fenestration of straight sinus (arrow). On basis of A alone, sinus thrombosis is difficult to exclude. However, other imaging series, including unenhanced T1-weighted and FLAIR images (not shown), fail to show abnormal signal intensity to suggest presence of a true thrombus, raising suspicion that this may have another cause. Two-dimensional TOF MR venogram (B) shows fenestration. Note small vessels representing fenestration are round and positioned on opposite sides of expected course of straight sinus. This appearance is unusual for residual patent lumen of dural venous sinus filled with thrombus because residual lumen tends to be irregular or crescent-shaped.

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9B —29-year-old woman woman with headache. Contrast-enhanced T1-weighted image (A), source image of 2D time-of-flight (TOF) MR venography (B), and maximum-intensity-projection of 2D TOF MR venography image (C) show fenestration of straight sinus (arrow). On basis of A alone, sinus thrombosis is difficult to exclude. However, other imaging series, including unenhanced T1-weighted and FLAIR images (not shown), fail to show abnormal signal intensity to suggest presence of a true thrombus, raising suspicion that this may have another cause. Two-dimensional TOF MR venogram (B) shows fenestration. Note small vessels representing fenestration are round and positioned on opposite sides of expected course of straight sinus. This appearance is unusual for residual patent lumen of dural venous sinus filled with thrombus because residual lumen tends to be irregular or crescent-shaped.

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9C —29-year-old woman woman with headache. Contrast-enhanced T1-weighted image (A), source image of 2D time-of-flight (TOF) MR venography (B), and maximum-intensity-projection of 2D TOF MR venography image (C) show fenestration of straight sinus (arrow). On basis of A alone, sinus thrombosis is difficult to exclude. However, other imaging series, including unenhanced T1-weighted and FLAIR images (not shown), fail to show abnormal signal intensity to suggest presence of a true thrombus, raising suspicion that this may have another cause. Two-dimensional TOF MR venogram (B) shows fenestration. Note small vessels representing fenestration are round and positioned on opposite sides of expected course of straight sinus. This appearance is unusual for residual patent lumen of dural venous sinus filled with thrombus because residual lumen tends to be irregular or crescent-shaped.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10 —Superior sagittal sinus thrombosis in young woman (exact age unknown) on T1-weighted image. Sagittal T1-weighted images can be useful for depiction of extensive superior sagittal sinus thrombosis. However, bright signal of thrombus with methemoglobin (arrow) may mimic patent sinus on contrast-enhanced T1-weighted images and time-of-flight MR venography.

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11A —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Axial phase contrast MR venogram shows loss of flow signal (arrow).

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11B —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Axial T1-weighted image fails to show thrombus.

View larger version (142K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11C —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Axial T1-weighted gadolinium-enhanced image shows smooth enhancement in hypoplastic left transverse and sigmoid sinuses.

View larger version (49K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11D —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Coronal reformations of CT venography, from posteriorly to anteriorly, show smooth enhancement in hypoplastic left transverse and sigmoid sinuses. Hypoplasia of ipsilateral jugular foramen also serves as important corroborative evidence of hypoplastic dural sinus.

View larger version (85K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11E —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Coronal reformations of CT venography, from posteriorly to anteriorly, show smooth enhancement in hypoplastic left transverse and sigmoid sinuses. Hypoplasia of ipsilateral jugular foramen also serves as important corroborative evidence of hypoplastic dural sinus.

View larger version (91K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11F —25-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses. Coronal reformations of CT venography, from posteriorly to anteriorly, show smooth enhancement in hypoplastic left transverse and sigmoid sinuses. Hypoplasia of ipsilateral jugular foramen also serves as important corroborative evidence of hypoplastic dural sinus.

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

Pitfalls on Unenhanced CT
Hyperdense blood in patent dural sinuses may mimic thrombosis. Hyperdense blood may be seen in children, particularly neonates and infants, and in patients with a hemoconcentration of the blood, as might be present in polycythemia or dehydration. At times, hyperdense blood may be difficult to differentiate from true dural venous thrombosis, but symmetry of involvement, homogeneity of the hyperdensity, and involvement of virtually all visualized dural venous sinuses and major venous structures should suggest that hyperdense blood is present rather than venous thrombosis (Figs. 5A and 5B). The presence of normal flow void in the venous sinuses should confirm the presence of patent sinuses. Hyperdense blood may also mimic subdural hemorrhage on CT, but the symmetry of apparent involvement, the limitation of the hyperdensity in the expected lumen of the dural sinuses, and a negative MRI study would effectively exclude this possibility (Figs. 5C and 5D).

Subdural hematoma may mimic CVT (Figs. 6A, 6B, 6C, 6D, 6E, 6F and 8A, 8B). The clue to the correct interpretation is that the abnormal signal of the subdural hematoma is located more medial than the expected location of the transverse sinus. Figure 6A, 6B, 6C, 6D, 6E, 6F shows the abnormal FLAIR signal extending too far inferiorly and medially, beyond the expected location of the normal transverse and sigmoid sinuses. Contrast-enhanced MR venography (Fig. 6F) confirms patent dural venous sinuses and no evidence of thrombosis.

CVT may mimic subdural hematoma (Fig. 7A, 7B, 7C, 7D, 7E, 7F, 7G). CVT should be confined entirely in the expected lumen of the dural venous sinuses. On the contrary, subdural hemorrhage is seen exterior to the dural venous sinuses. Patients with subdural hemorrhage in the posterior fossa may be at risk for CVT (possibly as a result of direct injury of the dural venous sinuses or venous stasis). In a patient with preexisting subdural hematoma, increasing density at the location of the dural venous sinuses should prompt consideration of the possibility of CVT (Fig. 7A, 7B, 7C, 7D, 7E, 7F, 7G).

View larger version (159K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12A —74-year-old man with headache and mastoiditis. Contrast-enhanced T1-weighted image shows filling defects (arrows) in bilateral transverse sinuses.

View larger version (139K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12B —74-year-old man with headache and mastoiditis. Maximum-intensity-projection of contrast-enhanced MR venography using sagittal 3D spoiled gradient-recalled echo (SPGR) sequence. Diagnosis is suggested by presence of normal patent flow immediately proximal and distal to filling defects, continuity of defects with dural surface, localized round or lobulated appearance, and central enhancement.

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13A —Arachnoid granulations simulating thrombus in dural venous sinuses. In conventional angiography of 16-year-old boy with developmental venous anomaly (long arrow), persistent filling defect is seen in right transverse sinus (short arrow).

View larger version (148K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13B —Arachnoid granulations simulating thrombus in dural venous sinuses. Contrast-enhanced T1-weighted image in same patient as in A shows soft-tissue structure (black arrow) at corresponding location. This structure is round and well defined, consistent with arachnoid granulation.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13C —Arachnoid granulations simulating thrombus in dural venous sinuses. Coronal T2-weighted image in different patient, 40-year-old man, shows typical round arachnoid granulation in left transverse sinus (arrow) that is abutting superior medial wall of transverse sinus. Normal flow void is seen adjacent to this structure (at arrow tip) and in consecutive images (not shown), further supporting this is an arachnoid granulation.

Pitfalls on Contrast-Enhanced CT
An empty delta sign may be mimicked by intrasinus septa or by a split or fenestrated dural sinus, which may manifest as false-positive filling defects.

Pitfalls on MRI
Intrasinus septa or a split or fenestrated dural sinus may also mimic CVT on MR images (Fig. 9A, 9B, 9C). Acute and early subacute hemorrhage may show hypointensity on T2-weighted MR images, mimicking the flow void that would normally be seen in a patent venous sinus. Thrombus with methemoglobin may mimic a patent sinus on contrast-enhanced T1-weighted MR images (Fig. 10). Slow flow leading to loss of flow void may mimic thrombosis.

View larger version (144K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 14A —6-year-old boy with neuroblastoma. T1-weighted image shows isointense lesion (arrow) at region of left transverse sinus, simulating sinus thrombosis.

View larger version (158K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 14B —6-year-old boy with neuroblastoma. Contrast-enhanced T1-weighted image shows enhancing lesion (black arrow) is dural extension of neuroblastoma, compressing lateral sinus (white arrow). Mass lesion is also seen posterior to torcular Herophili, compressing and displacing it anteriorly. Note mass lesion at lateral wall of left orbit.

View larger version (131K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 15A —42-year-old woman with headache. Coronal FLAIR image shows hyperintensity in subarachnoid space, consistent with subarachnoid hemorrhage.

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 15B —42-year-old woman with headache. Sagittal gadolinium-enhanced T1-weighted image shows extensive filling defects in superior sagittal sinus, straight sinus, and torcular Herophili (arrows).

View larger version (113K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 15C —42-year-old woman with headache. Coronal gadolinium-enhanced T1-weighted image confirms that loss of flow void in A represents thrombosis of superior sagittal sinus. Note filling defect of thrombus, giving rise to empty delta sign (arrow).

Thrombus with methemoglobin may show hyperintensity and mimic patent flow on TOF MR venography (Fig. 10). If in doubt, phase contrast venography (which depends only on blood flow characteristics and is not affected by the hyperintensity of methemoglobin) can be performed to clarify the findings.

Pitfalls on All Techniques
A hypoplastic or aplastic dural sinus may mimic CVT. Figure 11A, 11B, 11C, 11D, 11E, 11F shows a hypoplastic left transverse sinus. MR venography (Fig. 11A) can be misleading if it is interpreted in isolation. The significant change in blood flow dynamics in stenotic or hypoplastic dural venous sinuses can give rise to loss of flow signal (Fig. 11A). Unenhanced T1-weighted images (Fig. 11B) fail to show thrombus, which should be evident given the severe narrowing of the left dural sinuses. On the contrary, conventional gadolinium-enhanced T1-weighted images (Fig. 11C) show smooth enhancement in the hypoplastic left transverse and sigmoid sinuses, which is subsequently confirmed on CT venography (Figs. 11D, 11E, 11F). Hypoplasia of the ipsilateral jugular foramen (Figs. 11E and 11F) also serves as important corroborative evidence of a hypoplastic dural sinus. The case illustrated in Figure 11A, 11B, 11C, 11D, 11E, 11F highlights the importance of correlating MR venography or CT venography with conventional imaging findings.

Intrasinus arachnoid granulation may mimic thrombus (Figs. 12A, 12B and 13A, 13B, 13C). Figure 12A, 12B shows arachnoid granulations in the bilateral transverse sinuses. These granulations are also known as pacchionian granulations. In a series of autopsies of 10 patients with no known venous disease, giant arachnoid granulations were found in two patients, suggesting they are quite common [16]. Arachnoid granulation may show central and inhomogeneous contrast enhancement [16] (Fig. 13A, 13B, 13C).

Tumor invasion or tumor compression of dural sinuses may mimic CVT (Fig. 14A, 14B). However, tumor invasion or compression is a predisposing factor in the development of CVT, so this possibility should be explicitly excluded in these circumstances.

Subarachnoid hemorrhage can be one presentation of dural venous thrombosis [1, 8] (Fig. 15A, 15B, 15C). In such cases, careful review of the images may show abnormal signal in the lumen of the affected dural sinus, consistent with concurrent venous thrombus. MR venography can be used to confirm the presence of extensive dural sinus thrombosis by showing loss of flow void and filling defects.

Conclusion

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

 
The clinical presentation of CVT is nonspecific. To avoid a delay in diagnosis, radiologists need to be aware of the various imaging features of CVT, which can be subtle. Diagnostic pitfalls are associated with all imaging techniques, but can be avoided by careful correlation of all imaging findings.

Patients with low clinical suspicion of an intracranial abnormality can be screened with unenhanced CT. If in doubt, further workup may include CT venography or MRI with MR venography. CT venography and contrast-enhanced MR venography are probably comparable in accuracy for evaluating CVT, and the technique of choice will depend on the experience and resources of individual institutions. Conventional angiography is usually reserved for difficult cases or performed in conjunction with neurointervention.

References

Top Abstract Introduction Predisposing Factors Clinical Presentation Neuroradiology Diagnostic Pitfalls Conclusion References

 

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