Pictorial review of intracranial MRV techniques, pitfalls, and common pathologies involving the...
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Transcript of Pictorial review of intracranial MRV techniques, pitfalls, and common pathologies involving the...
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.
References• Leach JL, Fortuna RB, Jones BV, Gaskill-Shipley MF. Imaging of cerebral venous
thrombosis: current techniques, spectrum of findings, and diagnostic pitfalls. Radiographics. 2006;26 Suppl 1:S19-41
• Poon CS, Chang JK, Swarnkar A, Johnson MH, Wasenko J. Radiologic diagnosis of cerebral venous thrombosis: pictorial review. AJR Am J Roentgenol. 2007;189(6 Suppl):S64-75
• 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
Neuroradiol. 2005;26(1):50-5• Carr JC, Carroll TJ (2012). Magnetic Resonance Angiography: Principles and Applications.
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