Pictorial review of intracranial MRVtechniques, pitfalls, and common pathologies

involving the cerebral venous system

Jennifer Trinh, MDRajul Pandit, MD

Mahesh R. Patel, MD

Santa Clara Valley Medical Center, San Jose, CA

Control #806eEdE-44

Disclosures

• There are no financial disclosures.

Objectives

• Know the advantages and disadvantages of two non-contrast based MR venography (MRV) techniques and their pitfalls

• Review the anatomy of the cerebral venous system

• Know the common sites of cerebral venous thrombosis (CVT)

• Illustrate common etiologies of CVT and occlusion

Introduction

• The cerebral venous system can be difficult to evaluate due to artifacts, variant anatomy, and overlapping signal intensities of venous flow.

• Several MRV methods are available to image the intracranial venous system.

• These methods include both non-contrast and contrast based techniques.

MRV Techniques

• Two non-contrast based MRV techniques are utilized at our institution.– 2-D time of flight (TOF) MRV is obtained with the source data in

the coronal plane. – 3-D phase contrast MRV is obtained with the source data in the

sagittal plane.

• Contrast-enhanced MRV is another technique that is used at other institutions.– This technique relies on the paramagnetic effect of intravenous

gadolinium to shorten T1 and provide intravascular contrast enhancement.

Signal Generation in Non-Contrast MRV

• Time of Flight– TOF uses flow phenomenon for signal generation. Blood flowing into

the slice is not saturated and appears bright relative to the dark (suppressed) background. A saturation band is applied above the slice to suppress inflowing arterial signal.

• Phase Contrast– Spins that are moving in the same direction as a magnetic field

gradient develop a phase shift that is proportional to the velocity of the spins. Bipolar gradients (two gradients with equal magnitude but opposite direction) are used to encode the velocity of the spins.

– The signal in the vein depends on the velocity of the flowing blood and the velocity encoding by the technician.

Comparison of MRV TechniquesTechnique Advantages Disadvantages

TOF • Shorter imaging time• No special pulse sequences are

required

• More prone to false-positives from in-plane flow

Phase contrast • Better background suppression• Can detect flow in all 3

orthogonal planes• Better flow quantification• No false-negatives due to

methemoglobin

• More sensitive to motion artifacts and turbulent flow

• More arterial signal

Contrast enhanced • Less likely to give false-positives due to slow or complex flow

• Potential false negatives due to methemoglobin or enhancing chronic thrombus

AnatomyTOF Phase Contrast

Straight sinus

Straight sinus

Internal cerebral vein

Internal cerebral vein

Superior Sagittal Sinus Superior Sagittal Sinus

Transverse sinus

Sigmoid sinus

Sigmoid sinus

Internal jugular veins

Internal jugular

vein

Vein of GalenVein of Galen

Transverse sinus

Cerebral Venous System & Most Frequent Location of Thrombosis

TOF Phase Contrast

Straight sinus

Straight sinus

(18%)Internal

cerebral vein (12%)

Internal cerebral vein

Superior Sagittal Sinus (62%) Superior Sagittal Sinus

Transverse sinus (45%)

Sigmoid sinus

Sigmoid sinus

Internal jugular veins (12%)

Internal jugular

vein

Vein of GalenVein of Galen

Transverse sinus

Cortical veins (17%)

ARTIFACTS

In Plane Flow Artifact

In flow signal loss in the distal SSS in TOF sequence

Phase contrast imaging shows the SSS is patent

TOF Phase Contrast

Teaching Points:Common sites of signal loss include:• The distal portion of the SSS,

which is located in the coronal plane, on coronal TOF MRV.

• The horizontal portion of the SSS, the junction of the vein of Galen with the straight sinus, and the portions of the transverse sinus that are located in the axial plane on axial TOF MRV.

Internal cerebral veins

Obscuration of the internal cerebral veins by arterial inflow

Only one internal cerebral vein is visualized. The other is obscured by arterial inflow

TOF Phase Contrast

Arterial inflow in carotids

Arachnoid Granulations

Well defined extrinsic filling defect in the right transverse sinus

Teaching Points:• Arachnoid granulations are small

protrusions through the dura mater.

• They occur throughout the dural sinus, but most commonly in the transverse and superior sagittal sinus.

• Imaging shows a focal, well-defined, round filling defect with a characteristic anatomic distribution.

• Normal patent flow immediately proximal and distal to the filling defects further supports arachnoid granulations.

Phase Contrast

TOF TOF Source Data

Hypoplastic transverse sinus

Apparent signal loss in the transverse sinus is due to hypoplastic sinus

TOF Phase Contrast

Source TOF data shows a hypoplastic sinus Hypoplastic right transverse sinus on phase contrast

Teaching Points:• Hypoplasia or aplasia of one of the transverse sinuses is common.• Do not mistake for a sinus thrombosis!• Evaluate the source data.• If there is a CT, evaluate the jugular foramen size. A hypoplastic transverse

sinus will also have a small jugular foramen.

PATHOLOGIES

Venous Sinus Thrombosis64 year old female with headaches.

Teaching Points:• Mechanisms that lead to cerebral

venous thrombosis include direct involvement of the dural sinus (e.g. infection, trauma, tumor infiltration), hypercoagulable states, increased blood viscosity (e.g. dehydration), or venous stasis.

• Absence of a flow void and the presence of abnormal signal in the sinus is a primary finding of thrombosis on MRI. This should be further evaluated by MRV as slow or turbulent flow can also cause abnormal signal.

• An acute thrombus can be very hypointense on T2 and mimic a flow void.

Abnormal low T2 signal in the left lateral transverse sinus.

Left lateral transverse, sigmoid, and IJ are not seen, consistent with thrombosis.

Normal right transverse sinus flow void

Cortical Vein Thrombosis due to Spontaneous Intracranial Hypotension

46 year old female with orthostatic headaches for 10 days.

CT: Dense cortical veins.

Sag T1W: Sagging of cerebellar tonsils and posterior fossa structures with crowding of foramen magnum.

Axial GRE, FLAIR, T1WC+: blooming in the thrombosed cortical veins, subarachnoid hemorrhage in the parietal lobes, subdural hematomas, slit-like ventricles, and diffuse dural enhancement.

Cortical Vein Thrombosis due to Spontaneous Intracranial Hypotension

Teaching Points:• Dense cortical veins (cord sign) on CT is

a sign of cortical venous thrombosis.

• Imaging signs of intracranial hypotension include diffuse cerebral edema, cerebellar tonsillar herniation, sagging of the brainstem, and dural enhancement.

• Undiagnosed intracranial hypotension can result in subdural hematomas, subarachnoid hemorrhage, and dural venous sinus thrombosis.

• Isolated cortical vein thrombosis is rare. It may be associated with coagulation abnormalities or chronic inflammatory conditions such as inflammatory bowel disease.

No deep venous sinus thrombosis. Multiple dilated cortical veins along convexity.

Dilated cortical vein

Venous Infarction2 day old term infant with ongoing dusky spells of unclear etiology.

Marked restricted diffusion in the temporal lobe, consistent with acute infarction.

T1 hypointense, T2 hypointense signal with the area of infarction with blooming on GRE, consistent with hemorrhagic venous infarction. Venous infarcts often present with hemorrhage in the acute setting. Hemorrhagic transformation of an arterial infarct is less common and usually occurs later.

Venous Infarction & Thrombosis

TOF Phase Contrast

Hypoplastic left sigmoid sinus and IJ vein, better seen on phase contrast MRV.

Filling defect in the left transverse sinus, consistent with thrombus.

MRV from the same patient.

Artifactual loss of signal in the posterior SSS on TOF. SSS is patent on 3D velocity imaging.

Teaching Points:• Suspect venous infarct in a young patient, if the infarct does not correspond to a a

vascular territory, if there is a round area of hemorrhage, if it spares the cortex, or is in a bilateral parasagittal location.

• Evaluate the venous sinuses for a thrombus if there is a venous infarct.

Venous thrombosis due to venous epidural hematoma

Occipital fracture causing a venous epidural hematoma

Probable clot in the right transverse and sigmoid sinus junction

Active venous hemorrhage within the epidural hematoma

Medial aspect of right transverse sinus not visualized and may be injured.

Normal left venous sinuses

15 year old male brought in after a gang fight.

Venous thrombosis due to venous epidural hematomaMRV from the

same patient.

Source data shows the distal right transverse sinus is diminutive, but patent.

Occlusion of the right transverse venous confluence.

Cervical portion of left IJ vein not visualized and may be narrowed or occluded. There is an emissary vein providing an alternative drainage.

Mastoiditis with Right Internal Jugular Vein Thrombosis

Attenuated transverse & sigmoid sinuses

Normal left IJ vein

Normal left IJ vein

Normal left IJ vein

No signal in right IJ vein

Thrombosed right IJ vein

No signal in right IJ vein

Flow present proximal to thrombosis

Teaching Points:• Venous sinus thrombosis is a complication

of mastoiditis, although the incidence has declined due to antibiotic therapy.

• The sigmoid sinus and internal jugular vein should be carefully evaluated for thrombosis.

Compression from a Meningioma

T1WC+: Homogenously enhancing left parafalcine extra-axial mass that compresses the sagittal sinus at its dural attachment.

CTV: Left parafalcine meningioma compressing the sagittal sinus. Difficult to exclude focal thrombosis or invasion. Sagittal sinus around the mass is patent.

Compression from a Meningioma

Teaching Point:

If a mass compresses the venous sinus, a venogram should be performed to evaluate for thrombosis and invasion.

MRV MIP and source data: Mild irregularity and narrowing of the superior sagittal sinus at the region of the meningioma due to compression. No significant thrombosis or occlusion.

Compression from a Meningioma

T1WC+: Homogenously enhancing mass in the superior vermian cistern with a broad based dural tail extending along the tentorium.

MRV: Narrowing of the posterior two thirds of the straight sinus due to mass effect from the meningioma.

Occlusion from a Meningioma62 year old female with headache and papilledema.

T1WC+: Homogenously enhancing extra-axial mass in the posterior left cerebellopontine angle cistern. The mass closely abuts the left transverse sinus as it turns into the sigmoid sinus.

Occlusion from a MeningiomaMRV from the same patient.

Occlusion of the left transverse sinus at the level of the mass.

Flow is seen in the left IJ vein at the skull base.

Source data better depicts flow in the left sigmoid sinus and IJ vein

Thrombosis from a Schwannoma

Bilateral schwannomasFilling defect in the right transverse sinus due to thrombus

MRV shows thrombus in the distal right transverse sinus and narrowing in bilateral transverse sinuses due to mass effect. The right internal jugular vein is diminutive.

Occlusion from Squamous Cell Carcinoma70 year old male with chronic right mastoiditis and subperiosteal abscess.

TW1C+: Enhancing right mastoid mass.

T2W: Central T2 hypointense signal in the right transverse sinus.

TOF MRV: Distal right transverse, sigmoid sinus, and IJ vein are not seen, consistent with occlusion.

Thrombosis from RCC Metastasis

Nonenhanced CT: Soft tissue mass with osseous destruction of right occipital condyle, hypoglossal canal, and jugular foramen.

T1WC+ with fat saturation: Enhancing mass in the jugular foramen with occlusion of the jugular foramen.

Thrombosis from RCC Metastasis

TOF MRV: Filling defect in the right transverse sinus, consistent with clot.

Long segment of absent signal in right sigmoid & IJ vein, consistent with thrombosis and occlusion.

T2W: Enlarged right IJ vein with abnormal signal, consistent with thrombosis.

T1WC+: Filling defect in the right transverse sinus, consistent with clot.

Occlusion from Epidermoid• CT: Lobulated extra-axial mass in the left occipital

region with serpeginous ring and arc like calcifications within the mass. The mass erodes the occipital bone and posterior aspect of the temporal bone.

• Axial ADC map does not show low ADC signal.

• There are areas of high T1 and low GRE signal, consistent with hemorrhagic blood products.

• The majority of the mass is T2 hyperintense.

• The mass abuts the transverse and sigmoid.

Occlusion from EpidermoidMRV from the same patient.

MRV shows occlusion of the left transverse and sigmoid sinuses.

TOF Phase Contrast

Teaching Points:• The differential diagnosis of an

extra-axial mass with ring and arc like calcifications include hemangiopericytoma, chondrosarcoma, chordoma, and aggressive meningioma.

• This is an atypical appearance of an epidermoid, which did not demonstrate restricted diffusion.

Gustavo Saposnik et al. Stroke. 2011;42:1158-1192

Endovascular therapy may be considered in patients with absolute contraindications for anticoagulation therapy or failure of initial therapeutic doses of anticoagulant therapy.

Management of Cerebral Venous Thrombosis

Summary• Familiarity with common pitfalls of MRV will assist in the

accurate interpretation and diagnosis of the intracranial venous system.

• Correlating imaging findings on different MRV sequences and reviewing the source data can avoid diagnostic pitfalls associated with all imaging techniques.

• Knowledge of the typical and subtle imaging features of common pathologies of the cerebral venous sinuses will lead to prompt diagnosis and treatment, which can improve prognosis.

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• Ayanzen RH, Bird CR, Keller PJ et al. Cerebral MR venography: normal anatomy and potential diagnostic pitfalls. AJNR Am J Neuroradiol 2000:21:74–78

• Glockner JF, Lee CU. Magnetic Resonance Venography. Appl Radiol. 2010:39:36-42• Rollins N, Ison C, Booth T, Chia J. MR Venography in the Pediatric Patient. AJNR Am J

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Chicago, IL: Springer.• Saposnik G, Barinagarrementeria F, Brown RD Jr, Bushnell CD, Cucchiara B, Cushman M,

deVeber G, Ferro JM, Tsai FY; American Heart Association Stroke Council and the Council on Epidemiology and Prevention. Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2011;42(4):1158-92

Contact Information

Jennifer Trinh, MDDepartment of Radiology

Santa Clara Valley Medical Center751 S. Bascom Ave.San Jose, CA 95125

Jennifer.trinh@hhs.sccgov.org