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S64 AJR:189, December 2007

AJR Integrative Imaging

LIFELONG LEARNING

FOR RADIOLOGY

Radiologic Diagnosis of Cerebral Venous Thrombosis:

Pictorial ReviewColin S. Poon1,2, Ja-Kwei Chang1, Amar Swarnkar1, Michele H. Johnson2, John Wasenko1

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

DOI:10.2214/AJR.07.7015

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

1Department of Radiology, State University of New York Upstate Medical University, 750 E Adams St ., Syracuse, NY 13210. Address correspondence to C. S. Poon ([email protected]).

2Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT.

AJR2007;189:S6 4S75 0361 803X /07/1886S6 4 American Roentgen Ray Society

ObjectiveCerebral venous thrombosis is often associated with non-

specic clinical complaints. In addition, the imaging nd-

ings are often subtle. Underdiagnosis or misdiagnosis of ce-

rebral venous thrombosis can lead to severe consequences,

including hemorrhagic infarction and death.

Conclusion

This article reviews the radiologic ndings and diagnosticpitfalls of cerebral venous thrombosis. After completing this

article, the readers should have an improved ability to diag-

nose cerebral venous thrombosis accurately, using the opti-

mal imaging tools to achieve this goal.

IntroductionCerebral 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 non-

specic, 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 diag-nosis 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 presenta-

tion and basic pathophysiology of the disease; review the ap-

proach for radiologic investigation, including emerging technol-

ogy such as CT venography; review the imaging features of CVT;

and show common pitfalls associated with the radiologic evalua-

tion of this diagnosis. We have included many cases to illustrate

the radiologic features of CVT. Whenever possible, ndings on

different imaging techniques are correlated and compared.

Predisposing FactorsThe list of factors associated with CVT is too extensive to

be memorized [17]. A more manageable approach is to un-

derstand that they may involve one or more of the following

mechanisms: direct involvement of the dural sinuses (e.g.,

infection, trauma, neoplastic inltration), possibly with

damage to the vascular endothelium; venous stasis; hyperco-

agulable 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. Fre-

quent causes in older children include local infection, such as

mastoiditis, and coagulopathy. In adults, intrinsic or acquiredcoagulopathies become the most important factors, contrib-

uting 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 fac-

tors. CVT actually occurs more often in puerperium than dur-

ing 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 2035% of cases, the cause remains unknown;

therefore, one should remain suspicious, even in the absence

of known risk factors [13].

Clinical PresentationThe clinical presentation of CVT is often nonspecic [16]

(Table 1). Common presentation includes headache, focal neuro-

logic decits, 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 pa-

tients considered for the diagnosis of benign intracranial hyper-

tension [1]. Although subarachnoid hemorrhage is a rare presen-

tation of CVT, cases have also been reported [1, 8]. There is also

a wide distribution in the mode of onset of symptoms, with ap-

proximately 28% acute (< 48 hours), 42% subacute (between 48

hours and 30 days), and 30% chronic (> 30 days) [1]. The teach-

ing 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 neu-

roradiologic case.

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AJR:189, December 2007 S65

A

A

D

B

B

C

Fig. 15-year-old boy with severe headache and eye pain. Thrombosis was found in right lateral sinus (arrows).Aand B,Unenhanced CT images show thrombosis as hyperdensity (dense clot sign).Cand D,Enhanced CT images show same structure as filling defect wi th enhancing rim (empty delta sign).

Fig. 2Cord sign in cortical venous thrombosis in ayoung woman.Aand B,Unenhanced CT scans show dense corticalveins (white arrows,A), an uncommon direct sign ofcerebral venous thrombosis (CVT) known as cordsign. Note also indirect signs of CV T, including sub-cortical hemorrhagic infarction (black arrows), dif-fuse brain swelling, and small ventricular size.

Cerebral Venous Thrombosis

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NeuroradiologyUnenhanced CT remains the technique of choice for

screening patients with nonspecic clinical presentation

and a low suspicion of CVT. Contrast-enhanced CT provides

a more accurate diagnosis of CVT. MRI and MR venogra-

phy have been the noninvasive imaging techniques of choice[46, 9] and are often used as the initial diagnostic test for

suspicious cases. CT venography is now emerging as a com-

peting technique. It has been shown to be comparable to

MR venography and, in some situations, to provide better

diagnostic information [10].

Unenhanced CT

Direct signs of CVT are uncommon and are seen in only

one third of cases. Direct visualization of thrombosis in du-

ral sinus may give a dense clot sign (Fig. 1). The cord sign

represents direct visualization of a thrombosed cortical

vein that is seen as linear hyperdensity (Fig. 2).

More often, unenhanced CT shows only the indirect signs

of CVT. These are often nonspecic and may include diffuse

brain edema, leading to hypodensity of the brain (seen in2050% of cases) or decreased ventricular size. In young

patients, the pathologic decrease in ventricular size may be

difcult to differentiate from the normally small ventricles

commonly seen in young patients.

Venous infarction is the most specic indirect sign on unen-

hanced CT images. An infarction not conforming to a major

arterial vascular territory, such as the presence of multiple iso-

lated lesions, involvement of a subcortical region with sparing

of the cortex, and extension over more than one arterial distri-

A

D

B

E

C

F

Fig. 338-year-old woman wit h history o f pseudotumor cerebri who presented wi th headache and decreased consciousness. Diagnosis was thrombosis of superior

sagittal sinus, st raight sinus, and internal cerebral veins.(Long white arrowsindicate superior sagittal sinus; short white arrows, straight sinus; black arrows, Rosen-thal s veins).Aand B,Unenhanced CT scans show dense thrombosis. Note nonhemorrhagic infarction in basal ganglia, thalami, and int ernal capsules, which is typically seen indeep cerebral venous thrombosis.C,Axial T 2-weighted MR image shows replacement of signal void by thrombus (arrow) in superior sagittal sinus. Veins at i nternal capsules are engorged.Dand E,Sagitt al contrast-enhanced T1-weighted image (D) shows filling defects in sagitt al and straight sinuses, correlating with absence of flow on 2D phase con-tras t MR venography (E).F,After catheter-directed thrombolysis, flow was partially reestablished.

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bution, is highly suspicious for a venous cause. The infarction

may be hemorrhagic (Fig. 2) 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 im-

paired venous drainage and, therefore, parenchymal change inthe parasagittal region. Thrombosis in Labbs 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. 3).

Contrast-Enhanced CT

Direct evidence of CVT on contrast-enhanced CT includes

the empty delta sign, which may be seen 5 days to 2 months

from onset. This sign represents a lling defect (thrombus) in

the dural sinus, with peripheral enhancement possibly sec-

ondary to the development of collaterals (Fig. 1).

Indirect evidence of CVT may be seen as contrast enhance-

ment of the falx and tentorium secondary to venous stasis

and hyperemia of the dura mater, which is seen in approxi-

mately 20% of cases.One should be aware that in 1030% of cases of CVT, the nd-

ings 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 [1012]. CT venography allows direct visu-

alization of thrombus as lling defects (Fig. 4).


A

D E F

B C

Fig. 416-year-old girl with multiple traumatic injuries in head. Initial unenhanced CT (not shown) showed hyperdensity in right internal jugular vein (IJV) and sig-moid sinus that w as suspicious for venous thrombosis. Findings were con firmed on CT venography, MRI, and convent ional venography.Aand B,Axial source images from CT venography. Thrombus in IJV (asterisk,

A) and sigmoid sinus (black arrow,

B) is clearly shown as filling defect. Note collateralveins (white arrow,A) arising from right IJV.C,Sagittal planar reconstruction of CT venography shows thrombus extending from right IJV ( asterisk) into sigmoid sinus (arrow), correlating well with findings onconventional venography (E).D,T1-weighted MR image shows sigmoid sinus thrombosis (arrow) as seen on CT (B).E

and

F,

Venogram (E) shows thrombus as filling defects. Not e collateral veins at region of right IJVs, also seen in A. Venogram after suction thrombectomy (F) showsimproved patency in right IJV and lat eral sinus. Asterisk, right internal jugular vein; solid arrow, sigmoid sinus; open arrow, torcular Herophili.


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MRI

On MRI, venous thrombus may be directly visualized. On

conventional MRI sequences, patent dural sinuses are often

seen as a ow void. This is particularly well seen when the

imaging plane is orthogonal to the blood ow direction (e.g.,

coronal images are best for visualization of the superior sag-

ittal, transverse, and sigmoid sinuses). The effect of a ow

void may be reduced in a plane parallel to the dural sinus,

although such an imaging plane often offers a better depic-

tion of the complete extent of thrombosis in the dural sinus.For example, a sagittal T1-weighted image may show the

complete extent of the superior sagittal sinus thrombosis as

an abnormally bright signal lling the sinus. The thrombus

may manifest as absence of a ow void, which is often best

seen on FLAIR images and T2-weighted spin-echo images.

The abnormal signal intensity follows the signal characteris-

tics of intracranial hemorrhage and may evolve through the

stages of oxyhemoglobin, deoxyhemoglobin, methemoglo-

bin, and hemosiderin [4]. On T1-weighted images, thrombus

A CB

D

Fig. 54-day-old neonatal boy after idiopathic cardiac arrest.A

and

B,

Axial unenhanced CT scans show normal, hyperdense blood commonly seen in neonates and in-

fants.Cand D,T1- (C) and T2-weighted (D) MR images show normal findings.

TABLE 1: Signs and Symptoms of Cerebral

Venous Thrombosis

Presentation Frequency (%)

Headache 75

Papilledema 49

Seizures 37

Motor or sensory deficit 34

Mental status changes 30

Dysphasia 12

Cranial nerve palsies 12

Cerebellar incoordination 3

Bilateral or alternating cortical signs 3

Nystagmus 2

Hearing loss 2

NotePercentages total > 100% because patients may have multiple presentations.

Adapted from [1].

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with methemoglobin is seen as hyperintensity. On T2*-weighted

gradient-echo images, exaggerated signal loss is often seen

because of the increased susceptibility effect of deoxyhemo-globin, methemoglobin, or hemosiderin.

Indirect evidence of venous thrombosis is often second-

ary to parenchymal change as a result of venous occlusion.

This is similar to the ndings on CT, including brain swell-

ing and hemorrhagic or nonhemorrhagic infarction.

Conventional MRI sequences often provide sufcient in-

formation to raise the suspicion or to make a diagnosis of

CVT. The diagnosis can then be further conrmed on MR

venography or CT venography.

MR Venography

MR venography may be performed without the use of a

contrast agent using the time-of-ight (TOF) technique orthe phase contrast technique. Because these techniques use

MR ow phenomena for contrast generation, they are sub-

ject to ow-related image artifacts.

Similar to CT venography, contrast-enhanced MR venog-

raphy takes advantage of luminal lling by contrast material

rather than relying on the MR ow phenomena as in TOF or

phase contrast MR venography. Therefore, contrast-enhanced

MR venography is less likely to be affected by complex ow.

Recently, gadolinium-enhanced MR venography has been

A

D E F

B C

Fig. 6Middle-aged woman (exact age unknown) with histor y of multiple myeloma.Aand B,Axial unenhanced CT images show subdural hemorrhage at right cerebellar convexity that mimics thrombosis of r ight transverse sinus.CE,Axial FLAIR image (C), coronal FLAI R image (D), and unenhanced CT scan (E) at location adjacent to Bshow similar finding of subdural hemorrhage (white arrow,E) medial to right transverse sinus (black arrow,E).F,Contrast-enhanced MR venogram shows patent dural venous sinuses. Right transverse sinus (arrows) is smaller and slightly irregular compared with lef t, possiblysecondary to mass effect f rom adjacent subdural hematoma.


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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.

Comparison of MR Venography and CT Venography

A comparison of CT venography and MR venography is

summarized in Table 3.

CT venography has been shown to be superior to traditional

MR venography techniques based on 2D TOF or phase con-

trast techniques [10]. However, a direct comparison between

CT venography and contrast-enhanced MR venography is not

yet available. These two techniques probably provide compa-

rable performance, and preference will be dictated by the expe-

rience and resources of the individual institutions.

A

D

G

E F

B C

Fig. 77-year-old girl with closed head injur y.AC,Unenhanced CT scans on first day show subdural hemorrhage along tentorium cerebelli and skull frac-ture. Subt le densi ty is s een in righ t lateral sinus (arrows,

BandC) that was not well appreciated initially.Dand E,On next day, repeat CT scan shows dense thrombus in right lateral sinus (arrows) mimicking sub-dural hematoma (compare Ewith A).F

and G,On sagitt al T1-weighted MR images, normal flow void is seen in left lateral sinus (arrow,F), but note

isodense thrombus on right (arrow,G).

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TABLE 2: Comparison of MR Venography Techniques

Technique Advantages Disadvantages

Time-of-flight Shorter imaging time More prone to false-positive results from in-plane flow

False-negatives due to methemoglobin

Phase contrast Better background suppression More sensitive to motion artifacts and turbulent flow

Can detect flow in all three orthogonal planes

Better flow quantification

No false-negatives due to methemoglobin

Gadolinium-enhanced Less likely to give false-positives due to slow or

complex flow

Potential false-negatives due to methemoglobinaor

enhancing chronic thrombosis

aBut less likely than with time-of-flight.

A B

Fig. 84-month-old girl with seizure.A and B, Unenhanced CT scans show subduralhemorrhage along falx and tentorium cerebelli,simulating sagittal and transverse sinus thrombo-sis. Note pseudo empty delt a sign (arrow,A). Emptydelta sign of cerebral venous thrombosis is appli-cable only on contrast-enhanced CT. Hyperdensityalong posterior parietal convexity simulates trans-verse sinus thrombosis (black arrow,B). Extensionof hyperdensity beyond expected location of trans-verse sinus suggests this is actually subdural he-matoma (white arrow,B) [8].

A B C

Fig. 929-year-old woman woman wit h headache.AC,Contrast-enhanced T1-weighted image (A), source image of 2D time-of-flight ( TOF) MR venography (B), and maximum-intensit y-projection of 2D TOF MR venog-raphy image (C) show fenestration of straight sinus (arrow). On basis of Aalone, sinus thrombosis is difficult to exclude. However, other imaging series, includingunenhanced T1-weighted and FLAIR images (not shown), fail to show abnormal signal intensity to suggest presence of a true thrombus, raising suspicion that thismay have another cause. Two-dimensional TOF MR venogram (B) shows fenestrat ion. Note small vessels representing fenestrat ion are round and positioned on op-posite sides of expected course of s traight sinus. This appearance is unusual for residual patent lumen of dural venous sinus filled with t hrombus because residuallumen tends to be irregular or crescent-shaped.


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Diagnostic PitfallsPitfalls are associated with all imaging techniques [15].

To improve diagnostic accuracy, it is important to be aware

of these pitfalls. Always correlate ndings on multiple im-

aging sequences. If in doubt, other imaging techniques

should be used to conrm the ndings.

Pitfalls on Unenhanced CT

Hyperdense blood in patent dural sinuses may mimic

thrombosis. Hyperdense blood may be seen in children, par-

ticularly neonates and infants, and in patients with a hemo-

concentration of the blood, as might be present in poly-

cythemia or dehydration. At times, hyperdense blood may

be difcult to differentiate from true dural venous throm-

bosis, but symmetry of involvement, homogeneity of the

hyperdensity, and involvement of virtually all visualized

dural venous sinuses and major venous structures should

Fig. 10Superior sagittal sinus thrombosis in young woman (exact age un-known)

on T1-weighted image. Sagittal T1-weighted images can be useful fordepiction of extensive superior sagittal sinus thrombosis. However, bright sig-nal of thrombus with methemoglobin (arrow) may mimic patent sinus on con-tras t-enhanced T1-weighted images and t ime- of-fl ight MR venography.

A

D E F

B C

Fig. 1125-year-old woman with headache. Black arrows indicate left transverse and sigmoid sinuses; white arrows indicate right transverse and sigmoid sinuses.A,Axial phase contras t MR venogram shows loss of flow signal (arrow).B,Axial T1-weighted image fails to show thrombus.C,Axial T 1-weighted gadolinium-enhanced image shows smooth enhancement in hypoplastic left transverse and sigmoid sinuses.DF,Coronal reformations of C T venography, from posteriorly to anteriorly, show smooth enhancement in hypoplastic lef t transverse and sigmoid sinuses. Hypopla-sia of ipsilateral jugular foramen also serves as important corroborati ve evidence of hypoplastic dural sinus.

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suggest that hyperdense blood is present rather than venous

thrombosis (Figs. 5A and 5B). The presence of normal ow

void in the venous sinuses should conrm the presence of

patent sinuses. Hyperdense blood may also mimic subdural

hemorrhage on CT, but the symmetry of apparent involve-

ment, the limitation of the hyperdensity in the expected

lumen of the dural sinuses, and a negative MRI study wouldeffectively exclude this possibility (Figs. 5C and 5D).

Subdural hematoma may mimic CVT (Figs. 6 and 8). The

clue to the correct interpretation is that the abnormal signal of

the subdural hematoma is located more medial than the expect-

ed location of the transverse sinus. Figure 6 shows the abnormal

FLAIR signal extending too far inferiorly and medially, beyond

the expected location of the normal transverse and sigmoid si-

nuses. Contrast-enhanced MR venography (Fig. 6F) conrms

patent dural venous sinuses and no evidence of thrombosis.

CVT may mimic subdural hematoma (Fig. 7). CVT should be

conned entirely in the expected lumen of the dural venous si-

nuses. 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 ofdirect 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 consid-

eration of the possibility of CVT (Fig. 7).

Retained contrast material from previous radiologic ex-

aminations due to severely slow ow, such as might occur af-

ter ligation of the internal jugular vein, may mimic CVT.

A B

Fig. 1274-year-old man with headache and mas-toidit is.A,Contrast-enhanced T1-weighted image shows fill-ing defects (arrows) in bilateral transverse sinuses.B, Maximum-intensity-projection of contrast-en-hanced MR venography using sagittal 3D spoiledgradient-recalled echo (SPGR) sequence. Diagnosisis suggested by presence of normal patent flow im-mediately proximal and distal to filling defects, con-tinui ty of defects with dura l surface , localized roundor lobulated appearance, and central enhancement.

A B C

Fig. 13Arachnoid granulations simulating thrombus in dural venous sinuses.A,In conventional angiography of 16-year-old boy with developmental venous anomaly (long arrow), persistent filling defect is seen in right t ransverse sinus (short arrow).B,Contrast-enhanced T1-weighted image in same patient as in Ashows soft-tissue structure (black arrow) at corresponding location. This structure is round andwell defined, consistent with arachnoid granulation.C,Coronal T2-weighted image in different patient, 40-year-old man,

shows typical round arachnoid granulation in left transverse sinus (arrow) that is abutting supe-rior medial wall of transverse sinus. Normal flow void is seen adjacent to this struct ure (at arrow tip) and in consecutive images (not shown), furt her supporting thisis an arachnoid granulation.


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However, these conditions may also predispose the patient to

developing thrombosis, so a contrast-enhanced study should

be performed to clarify the ndings.

Pitfalls on Contrast-Enhanced CT

An empty delta sign may be mimicked by intrasinus sep-

ta or by a split or fenestrated dural sinus, which may mani-

fest as false-positive lling defects.

Pitfalls on MRI

Intrasinus septa or a split or fenestrated dural sinus may

also mimic CVT on MR images (Fig. 9). Acute and early sub-

acute hemorrhage may show hypointensity on T2-weighted

MR images, mimicking the ow 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 ow leading to loss of ow void may

mimic thrombosis.

Pitfalls on MR Venography

Signal loss on unenhanced MR venography may result

from in-plane ow, extremely slow ow, or complex ow,

mimicking thrombosis.

Thrombus with methemoglobin may show hyperintensity

and mimic patent ow on TOF MR venography (Fig. 10). If in

doubt, phase contrast venography (which depends only on blood

ow characteristics and is not affected by the hyperintensity of

methemoglobin) can be performed to clarify the ndings.

Pitfalls on All Techniques

A hypoplastic or aplastic dural sinus may mimic CVT. Figure

11 shows a hypoplastic left transverse sinus. MR venography

A B

Fig. 146-year-old boy with neuroblastoma.

A,T1-weighted image shows isointense lesion (ar-row) at region of left transverse sinus, simulatingsinus thrombosis.B, Contrast-enhanced T1-weighted image showsenhancing lesion (black arrow) is dural extension ofneuroblastoma, compressing lateral sinus (white ar-row). Mass lesion is also seen posterior to torcularHerophili, compressing and displacing it anteriorly.Note mass lesion at lateral wall of left orbit .

A B C

Fig. 1542-year-old woman with headache.A,Coronal FL AIR image shows hyperintensit y in subarachnoid space, consistent wit h subarachnoid hemorrhage.B,Sagitt al gadolinium-enhanced T1-weighted image shows extensive filling defects in superior sagitt al sinus, straight sinus, and torcular Herophili (arrows).C,Coronal gadolinium-enhanced T1-weighted image confirms that loss of flow void in Arepresents thrombosis of superior sagittal sinus. Note filling defect of throm-bus, giving rise to empty delta sign (arrow).

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(Fig. 11A) can be misleading if it is interpreted in isolation. The

signicant change in blood ow dynamics in stenotic or hyp-

oplastic dural venous sinuses can give rise to loss of ow signal

(Fig. 11A). Unenhanced T1-weighted images (Fig. 11B) fail to

show thrombus, which should be evident given the severe nar-

rowing of the left dural sinuses. On the contrary, conventional

gadolinium-enhanced T1-weighted images (Fig. 11C) showsmooth enhancement in the hypoplastic left transverse and sig-

moid sinuses, which is subsequently conrmed on CT venogra-

phy (Figs. 11 D11F). Hypoplasia of the ipsilateral jugular fora-

men (Figs. 11E and 11F) also serves as important corroborative

evidence of a hypoplastic dural sinus. The case illustrated in

Figure 11 highlights the importance of correlating MR venogra-

phy or CT venography with conventional imaging ndings.

Intrasinus arachnoid granulation may mimic thrombus

(Figs. 12 and 13). Figure 12 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. 13).

Tumor invasion or tumor compression of dural sinuses

may mimic CVT (Fig. 14). However, tumor invasion or com-

pression is a predisposing factor in the development of CVT,

so this possibility should be explicitly excluded in these cir-

cumstances.

Subarachnoid hemorrhage can be one presentation of

dural venous thrombosis [1, 8] (Fig. 15). In such cases, care-

ful review of the images may show abnormal signal in the

lumen of the affected dural sinus, consistent with concur-

rent venous thrombus. MR venography can be used to con-rm the presence of extensive dural sinus thrombosis by

showing loss of ow void and lling defects.

Conclusion

The clinical presentation of CVT is nonspecic. To avoid a

delay in diagnosis, radiologists need to be aware of the vari-

ous 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 ndings.

Patients with low clinical suspicion of an intracranial ab-

normality 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 evaluat-

ing CVT, and the technique of choice will depend on the expe-

rience and resources of individual institutions. Conventionalangiography is usually reserved for difcult cases or performed

in conjunction with neurointervention.

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TABLE 3: Comparison of MR Venography and CT Venography

Technique Advantages Disadvantages

MR venography No radiation risk Cannot be used in patients with contraindication to MRI

Better established Unenhanced techniques more prone to flow-related image artifacts, leading to

higher incidence of false-positive results

CT venography Short imaging time Requires iodinated contrast agent

Less prone to motion artifacts

Generally better availability

More accessible for critical patients

Better depiction of small vessels

Easy to interpret

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