The MR-techniques that are used for the diagnosis of cerebral venous thrombosis are: Time-of-flight (TOF), phase-contrast angiography (PCA) and contrast-enhanced MR-venography: Time-of-Flight angiography is based on the phenomenon of flow-related enhancement of spins entering into an imaging slice.As a result of being unsaturated, these spins give more signal that surrounding saturated spins. Phase-contrast angiography uses the principle that spins in blood that is moving in the same direction as a magnetic field gradient develop a phase shift that is proportional to the velocity of the spins. This information can be used to determine the velocity of the spins. This image can be subtracted from the image, that is acquired without the velocity encoding gradients, to obtain an angiogram. Contrast-enhanced MR-venography uses the T1-shortening of Gadolinium.It is similar to contrast-enhanced CT-venography. When you use MIP-projections, always look at the source images.
T2 T1 TOF MR venography
An intrasinus thrombus in the subacute stage may have markedly increased signal intensity on MR images that may be misinterpreted as evidence of flow on TOF MR venograms
T1-shortening shine-through in a patient with thrombosis of the superior sagittal sinus and transverse sinuses. Lateral MIP image from coronal TOF MR venography shows an area of thrombosis with a signal of intermediate intensity (arrows) resembling that of normal sinus flow but less intense than that in patent cortical veins (arrowheads).
Contrast enhanced MR-venography is the most reliable MR technique. CT-venography is even more reliable, because it is easy and less sensitive to pitfalls
TOF MR venography, contrast-enhanced MR venography, and CT venography are the most useful techniques for diagnosis of this condition. Knowledge of normal venous variations and potential pitfalls related to image interpretation are important for achieving an accurate diagnosis.
Dense clot sign Dense cord sign empty delta sign
Flair - flow void
Thrombosis of the left transverse sinus in a 42-year-old woman. (a, b) Axial unenhanced CT images show left cerebellar and temporal hematoma with increased attenuation in the left transverse sinus (cord sign) (* in a). (c) On a 3D MIP image from CT venography, the left transverse sinus is not visible.
Normal MR sequences 1.T2 2.T1 3.Flair 4.DWI(diffusion weighted image) 5.ADC (Apparent diffusion coefficient) 6. GE (Gradient echo sequences) 7.T1 post contrast 8.MRV 9.3D MRV 10.MRA 11.T2 12.T1
Cerebral venous thrombosis
Cerebral Venous Thrombosis
Major dural sinuses:
• Superior sagittal sinus, transverse, straight and
• Vein of Labbe, which drains the temporal lobe.
• Vein of Trolard, which is the largest cortical vein that
drains into the superior sagittal sinus.
• Internal cerebral and thalamostriate veins.
CT scan of a 45-year-old woman with clinical suspicion of dural sinus thrombosis.
Lateral (A), anteroposterior (B), caudocranial (C), and oblique sagittal (D) MIP of
CTA data set after MMBE. The projections demonstrate normal appearance of the
superior sagittal sinus (arrowheads), the transverse sinuses (arrows), the deep
venous system, and the superficial cortical veins without any overlying bone
Indications For CT and MRI in
Indications for CT in suspected stroke
• Early diagnosis if possible
• Differentiation between ishcemic and
• Exclusion of stroke mimics-tumors
Indication for MRI
• If CT is normal and clinical suspicion high
• Assessment of diffusion and perfusion
• Detection of stroke in posterior fossa
• Detection of underlying cause
• Assessment of intra and extracranial vessels
by MR angiography
• Exclusion of venous sinus thrombosis
Appearance of Blood on Scans
• Acute –Higher attenuation than underlying
• Sub acute-Similar attenuation to brain
• Chronic-Lower attenuation than underlying
WT FAT H2O MUSC LIG BONE
T1 B D I D D
T2 I B I D D
WW2--> water white on T2 weighted image
Venous sinus thrombosis
• < 2% of all strokes
• Accounts for up to 50% of strokes during
pregnancy and puerperium
• Important cause of stroke especially in
children and young adults
• It is a difficult diagnosis because of its
nonspecific clinical presentation and subtle
Septic causes( especially in children)
• Sinusitis, Otitis, Mastoiditis, Sub/epidural
• Meningitis, encephalitis, Brain abscess, Face
and scalp cellulitis, septicemia
Trauma > Fracture through sinus wall,jugular vein
Low flow states > CHF, Dehydration ,Shock
• Dural sinus thrombosis leads to venous
congestion, venous infarction ,brain
edema and heamorrhage
• CT brain , CTV
• MRI brain and MRV
• Cerebral angiography
• Direct signs of a thrombus
• Infarction in a non-arterial location, especially
if it is bilateral and hemorrhagic
• Cortical or peripheral lobar hemorrhage
• Cortical edema
• Dense Clot sign on NECT
• Cord sign
• Empty delta sign on CECT
• Replacement of flow void by abnormal
signal intensity on MRI
• MRV absence of flow
• Non filling of thrombosed veins on
• Venous infarction, edema
ABSENCE OF NORMAL FLOW
VOID ON MR
Patent cerebral veins usually will
demonstrate low signal intensity due to flow
Flow voids are best seen on T2-weighted
and FLAIR images.
A thrombus will manifest as absence of flow
Due to the high venous pressure hemorrhage
is seen more frequently in venous infarction
compared to arterial infarction.
Often bilateral and in the midline in an atypical
location or in a non-arterial distribution.
CT-venography demonstrating thrombosis in many
Transverse MIP image of a Phase-Contrast angiography.
The right transverse sinus and jugular vein have no signal due to
Acute thrombus in a 35-year-old woman with a severe headache
for 5 days. Axial T2W MR image (a) and axial T1W MR image (b) show a thrombus in
the left sigmoid sinus (arrows). The signal in the thrombus, compared with that in
the normal brain parenchyma, is hypointense in a and iso- to hyperintense in b. (c)
Frontal MIP image from coronal TOF MR venography shows a lack of flow in the
distal portion of the left transverse sinus and the sigmoid sinus (arrows).
PITFALLS IN CT
Arachnoid granulations produce well-
defined focal filling defects within the dural
venous sinuses and measure 2–9 mm in
diameter. They are isoattenuating (one-
third) or hypoattenuating (two-thirds)
relative to brain parenchyma
Transverse sinus flow gap. (a) Coronal image from TOF MR venography
shows an apparent interruption of flow in the medial part of the left transverse sinus
(b) Oblique MIP image from contrast-enhanced MR venography shows enhancement
indicative of normal flow in the medial part of the left transverse sinus (arrow).