CVT

1. DEPARTMENT OF RADIO DIAGNOSIS
Dr.NIJALINGAPPA
PG IN RADIOLOGY
DEPARTMENT OF RADIO DIAGNOSIS
JJMMC
DAVANGERE

2. The syndrome of intracranial
venous and sinus thrombosis -
termed as cerebral venous
thrombosis(CVT)

3.  5-8 per 1 million population
 Increased frequency of diagnosis since advent
of DSA, CT & MRI/V.
 < 2% of all strokes
 Male/female ratio = 1.29/1
 Males uniform age distribution
 Females 61% CVT in 20-35 age group
 75% of adult patients are women (ISCVT
study)
 Accounts for up to 50% of strokes during
pregnancy and puerperium

4.  Superior sagittal sinus 72%
 Lateral sinus 70%
Right 26%
Left 26%
Both 18%
 Straight sinus 14.5%
 Cavernous sinus 2.7%
 Cerebral veins 38%
Superficial 27%
Deep 8%
 Cerebellar veins 3%

5.  One sinus only 23%
 Superior sagittal sinus 13%
 Lateral sinus 9%
 Straight sinus 1%
 Deep veins only 1%
 Isolated cortical veins 1%

6. Causes of and Predisposing Factors for Cerebral Venous Thrombosis
 Local conditions
Brain and skull damage
Intracranial and local regional infections(eg;mastoiditis)
 Systemic conditions
Hormonal (pregnancy or puerperium, estroprogestative
and steroid therapy)
Surgery, immobilization
Hematologic and hypercoagulable disorders
Connective tissue disease
Malignancy
Systemic infection
Dehydration
 Idiopathic causes (25%)

7.  Chronic Headache 75%
 Papilledema 49%
 Motor or sensory deficit 34%
 Seizures 37%
 Drowsiness, mental changes,confusion, or coma 30%
 Dysphasia 12%
 Multiple cranial nerve palsies 12%
 Cerebellar incoordiantion 3%
 Nystagmus 2%
 Hearing loss 2%
 Bilateral or alternating cortical signs 3%

8. Thrombosis and endogenous
thrombolysis and recanalization may occur
concurrently, the clinical manifestations
may fluctuate in as many as 70% of
patients, adding to clinical uncertainty.
Intracranial hypertension occurs
in 20%–40% of patients with cerebral
venous thrombosis and should be
excluded in patients with the specific
complex of symptoms

9. 1.Thrombosis of cerebral veins
Local effects caused by venous obstruction, oedema of
brain (both cytotoxic and vasogenic) and infarction due to
elevated venous and capillary pressure
complicated by haemorrhage – may be multiple and
bilateral, and not respect arterial vascular territories
2. Thrombosis of major sinuses
obstruction leads to impaired absorption of CSF and
intracranial hypertension
1/5 of patients with sinus thrombosis have intracranial
hypertension only without signs of cortical vein thrombosis

10. 1. CT
2. MRI/V
3. DSA
4. TCD
5. OTHERS: EEG, CSF, CRANIOTOMY, isotope brain
scanning

12. Normal sinovenous anatomy.
(a, b) Axial MIP CT image (a) and 3D volume-rendered image from CT venography
(oblique anterosuperior view) (b) show the internal cerebral veins (ICV), basal veins of
Rosenthal (BVR), vein of Galen (VOG), and straight sinus (StrS). On the volume-rendered
image, note the asymmetric appearance of the torcular herophili (TH), which is formed by
the union of the superior sagittal sinus (SSS),straight sinus, and transverse sinuses (TS).
The volume-rendered image also shows the sigmoid sinus (SS) and superficial middle
cerebral vein (SMCV). (c) Sagittal MIP CT image shows the inferior sagittal sinus (ISS), as
well as the internal cerebral vein, superior sagittal sinus, straight sinus, and vein of Galen.

13. Normal sinovenous anatomy. Three- Normal sinovenous anatomy.
dimensional integral image from CT Axial MIP CT image shows
venography (lateral view) shows the asymmetric transverse sinus(TS).
anastomotic vein of Trolard (AVOT) The sigmoid sinuses (SS) begin
draining into the superior sagittal sinus where the transverse sinuses
(SSS), the anastomotic vein of Labbe´ leave the tentorial margin. The
(AVOL) draining into the transverse sinus right cavernous sinus (CS) is also
(TS), and the superficial middle cerebral demonstrated.
vein (SMCV).

14. MIP image from contrast-enhanced MR venography, with a color overlay, demonstrates the superior
dural sinuses. They include the superior sagittal sinus (green), inferior sagittal sinus (light
blue), straight sinus(dark purple), confluence of the sinuses (orange), transverse sinuses (dark
blue), and sigmoid sinuses (yellow). The internal jugular veins and bulbs (light purple) also are
depicted. (2)lateral MIP image from contrast-enhanced MR venography, with editing of the deep veins
to improve the visibility of the ascending veins that drain into the superior sagittal sinus from the
lateral hemispheric cortex (the frontopolar [1], anterior frontal [2], and posterior frontal [3]veins;
Trolard vein [superior anastomotic vein] [4]; and anterior parietal veins [5]) and the larger named veins
on the
lateral surface of the cerebrum (the superficial sylvian vein [superficial middle cerebral vein] [6], which
typically drains into the sphenoparietal sinus or the cavernous sinus, and the Labbe´ vein [7], which
drains into the transverse sinus).

15. Axial MR image series with a color
overlay represents the major
superficial cortical venous drainage
territories according to Meder et al.
Most of the superior cerebrum
(green) is drained primarily into the
superior sagittal sinus,
which also receives drainage from
the parasagittal cortical regions at
lower levels.
The sylvian veins drain blood from
the peri-insular region (yellow) into
the basal dural sinuses.
The transverse sinuses receive
blood from the temporal, parietal,
and occipital lobes (blue).
The Labbe´ vein, if dominant,may
drain much of this territory.
Parenchymal abnormalities such as
hemorrhage or edema in this
territory may be indicative of
thrombosis of the transverse sinus
or Labbe´ vein.

17. Direct visualization of a clot in
the cerebral veins on a non
enhanced CT scan is known as
the dense clot sign.
It is seen in only one third of
cases.
Normally veins are slightly
denser than brain tissue and in
some cases it is difficult to say
whether the vein is normal or too
dense .
In these cases a contrast
enhanced scan is necessary to
solve this problem

18. On the left
images of a
patient with a
hemorrhagic
infarction in
the temporal
lobe (red
arrow).
Notice the
dense
transverse
sinus due to
thrombosis
(blue arrows).

19. 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.

20. The empty delta sign is a finding that is seen on a contrast enhanced
CT (CECT) and was first described in thrombosis of the superior
sagittal sinus.
The empty delta sign is seen in 25%–75%
The sign consists of a triangular area of enhancement with a
relatively low-attenuating center, which is the thrombosed sinus.
The likely explanation is enhancement of the rich dural venous
collateral circulation surrounding the thrombosed sinus, producing
the central region of low attenuation.
In early thrombosis the empty delta sign may be absent and you will
have to rely on non-visualization of the thrombosed vein on the
CECT.
The empty delta sign can disappear in chronic stages with
enhancement of organized clot or due to recanalization within the
thrombus

21. Two cases of empty delta sign due to thrombosis of the
superior sagittal sinus.

22. On the left a case
of thrombosis of
the right
transverse sinus
and the left
transverse and
sigmoid sinus
(arrows).
There is
enhancement
surrounding the
thrombosed
hypoattenuating
veins

23. On spin-echo images patent cerebral veins
usually will demonstrate low signal intensity due
to flow void.
Flow voids are best seen on T2-weighted and
FLAIR images, but can sometimes also be seen
on T1-weighted images.
A thrombus will manifest as absence of flow void.
Although this is not a completely reliable
sign, it is often one of the first things, that make
you think of the possibility of venous
thrombosis.
The next step has to be a contrast enhanced
study

24. On the left a T2-
weighted image
with normal flow
void in the right
sigmoid sinus
and jugular vein
(blue arrow).
On the left there
is abnormal high
signal as a result
of thrombosis
(red arrow).

25. The images on the left
show abnormal high signal
on the T1-weighted images
due to thrombosis.
The thrombosis extends
from the deep cerebral
veins and straight sinus to
the transverse and sigmoid
sinus on the right.
Notice the normal flow void
in the left transverse sinus
on the right lower image.
Absence of normal flow
void on MR-images can be
very helpful in detecting
venous thrombosis, but
there are some pitfalls .
Slow flow can occur in
veins and cause T1
hyperintensity.

26. The other sign that can help you in making the diagnosis
of unsuspected venous thrombosis is venous infarction.
Venous thrombosis leads to a high venous pressure
which first results in vasogenic edema in the white matter of
the affected area.
When the process continues it may lead to infarction and
development of cytotoxic edema next to the vasogenic
edema.
This is unlike in an arterial infarction in which there is
only cytotoxic edema and no vasogenic edema.
Due to the high venous pressure hemorrhage is seen
more frequently in venous infarction compared to arterial
infarction.
Since we are not that familiar with venous infarctions, we
often think of them as infarctions in an atypical location or in
a non-arterial distribution.

27. However venous infarctions do have a typical distribution
Since many veins are midline structures, venous infarcts are
often bilateral and hemorrhagic
This is seen in thrombosis of the superior sagittal
sinus, straight sinus and the internal cerebral veins.

28. Superior sagittal sinus thrombosis
The most frequently
thrombosed venous
structure is the superior
sagittal sinus.
Infarction is seen in 75% of
cases.
The abnormalities are
parasagittal and frequently
bilateral.
Hemorrhage is seen in 60%
of the cases.
On the left bilateral
parasagittal edema and
subte hemorrhage in a
patient with thrombosis of
the superior sagittal sinus.
Bilateral infarction in superior sagittal
sinus thrombosis

29. reconstructed sagittal CT-images in a patient with bilateral parasagittal
hemorrhage due to thrombosis of the superior sagittal sinus.
The red arrow on the contrast enhanced image indicates the filling
defect caused by the thrombus.

30. Another typical venous infarction
is due to thrombosis of the vein
of Labbé.
On the left images demonstrating
hypodensity in the white matter
and less pronounced in the gray
matter of the left temporal lobe.
.
Notice that there is some linear
density within the infarcted area.
This is due to hemorrhage.
In the differential diagnosis we
also should include a venous
infarct in the territory of the vein
of Labbe.
The subtle density in the area of
the left transverse sinus (arrow) is
the key to the diagnosis.
This is a direct sign of thrombosis
and the next step is a CECT,

31. On the left images of a
patient with hemorrhage
in the temporal lobe.
When the hemorrhagic
component of the
infarction is large, it may
look like any other
intracerebral hematoma
with surrounding
vasogenic edema.
The clue to the
diagnosis in this case is
seen on the contrast
enhanced image, which
demonstrates the filling
defect in the sigmoid
sinus (blue arrow).

32. On the left a similar case on
MR.
There is a combination of
vasogenic edema (red
arrow), cytotoxic edema and
hemorrhage (blue arrow).
These findings and the
location in the temporal
lobe, should make you think
of venous infarction due to
thrombosis of the vein of
Labbé.
The next examination should
be a contrast enhanced MR or
CT to prove the diagnosis.
Hemorrhagic venous infarct in Labbe
territory

33. On the far left a FLAIR image
demonstrating high signal in
the left thalamus.
When you look closely the
image, there is also high
signal in the basal ganglia
on the right.
These bilateral findings
should raise the suspicion of
deep cerebral venous
thrombosis.
A sagittal CT reconstruction
demonstrates a filling defect
in the straight sinus and the
vein of Galen (arrows).
Venous thrombosis of vein of Galen
and straight sinus

34. On the left a young patient with
bilateral abnormalities in the
region of the basal ganglia.
Based on the imaging findings
there is a broad differential
including small vessel disease,
demyelinisation, intoxication
and metabolic disorders.
Continue with the T1-weighted
images in this patient.
Notice the abnormal high signal
in the internal cerebral veins and
straight sinus on the T1-
weighted images, where there
should be a low signal due to
flow void.
This was unlike the low signal in
other sinuses.
The diagnosis is bilateral
infarctions in the basal ganglia
due to deep cerebral venous
thrombosis.
Bilateral infarctions in the basal ganglia due
to deep cerebral venous thrombosis

35.  CT-venography is a simple and straight forward
technique to demonstrate venous thrombosis.
In the early stage there is non-enhancement of the
thrombosed vein and in a later stage there is non-
enhancement of the thrombus with surrounding
enhancement known as empty delta sign, as discussed
before.
 Unlike MR, CT-venography virtually has no pitfalls.
The only thing that you don't want to do, is to scan too
early, i.e. before the veins enhance or too late, i.e. when
the contrast is gone.
Some advocate to do a scan like a CT-arteriography and
just add 5-10 seconds delay.
To be on the safe side we advocate 45-50 seconds delay
after the start of contrast injection.
We use at least 70 cc of contrast.

37.  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.

38. Transverse MIP image of a Phase-Contrast angiography.
The right transverse sinus and jugular vein have no signal
due to thrombosis.

39. Acute thrombus in a 35-year-old woman with a severe headache
for 5 days. (a, b) 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).

40. Angiography is only performed in severe cases, when an
intervention is planned.
On the left images of
a patient with venous
thrombosis, who was
unconscious and did
not respond to
anticoagulant
therapy.
There is thrombosis
of the superior
sagittal sinus (red
arrow), straight sinus
(blue arrow) and
transverse and
sigmoid sinus (yellow
arrow).

41. Arachnoid granulations
Arachnoid granulations of Pacchioni play a major role in the
resorption of cerebrospinal fluid. They are most commonly found
within the lacunae laterales of the superior sagittal sinus
Arachnoid granulations can also protrude directly into the
sinus lumen, adjacent to venous entrance sites, and should not
be mistaken for sinus thrombosis. Arachnoid granulations are
present in the superior sagittal sinus, transverse
sinus, cavernous sinus, superior petrosal sinus, and straight
sinus in decreasing order of frequency
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

42. Arachnoid granulations
of Pacchioni in the
venous sinuses. (a)
Sagittal 2D MIP image
from CT venography
show arachnoid
granulations (arrows) in
the superior sagittal
sinus and straight sinus.
(b) Axial contrast-
enhanced CT image
shows a well-limited
lobulated
defect (arrow) in the
right transverse sinus.

43. Classic appearance of
arachnoid granulations.
(a) Photograph from an
anatomic dissection of
the right transverse sinus
demonstrates focal
protuberances consistent
with arachnoid granulations
(arrows). Intrasinus septa
(chordae willisii)(arrowheads)
also are depicted.
(b, c) Axial contrast-
enhanced CT image (b)and
superoinferior MIP image
from contrast-enhanced MR
venography (c) show well-
defined focal filling defects
consistent with arachnoid
granulations in the lateral
part of the transverse sinus
(arrow), the most common
site of such findings.

44. Pseudodelta sign
The dense triangle sign can be
mimicked in infants by the
combination of the hypointensity
of the unmyelinated brain and the
physiologic polycythemia resultig
in high density of the blood in the
sagittal sinus.
A pseudodelta sign can also be
seen in patients with
hyperattenuating acute
subarachnoid hemorrhage around
the sinus or subdural empyema or
in patients with a posterior
parafalcine interhemispheric
hematoma.
In these cases, administration of
contrast material should opacify
the sinus, obliterating the lucent
center of the pseudodelta

45. Anomalous location of the superior sagittal sinus bifurcation
(a) Anteroposterior
MIP image from TOF MR
venography shows a high
bifurcation of the
superior sagittal
sinus (arrow). (b) On the
axial contrast-enhanced
CT image, the early
bifurcation of the sinus
produces a pseudo
empty delta sign (arrow),
mimicking sinus
thrombosis.

46. Normally veins are
slightly denser
than brain tissue
and in some cases
it is difficult to say
whether it is
normal or too
dense.
In these cases a
contrast enhanced
scan is necessary
to solve this
problem.
On the left an
image of a
thrombosed
transverse sinus
and next to it a
normal transverse
sinus.
Normal transverse sinus (lt) Thrombosed transverse sinus(rt).

47. Wrong bolus timing
Three images of a patient with venous thrombosis in the superior
sagittal sinus.
On the far left we see a dense vessel sign on the unenhanced CT.
In the middle an image made 25 seconds after the start of the
contrast injection.
There is arterial enhancement and it looks as if the superior sagittal
sinus enhances, but in fact what we see is the shine through of the
dense thrombus.
Only on the image on the right, which was made 45 seconds after
contrast injection there is an empty delta sign, which proves the
presence of a thrombus in the sinus.

48. Hematoma simulating venous thrombosis
Usually there is no
problem in
differentiating a
hematoma from a
thrombosed sinus.
On the left a patient
with a peripheral
intracerebral
hematoma, that on
first impression
simulates a
thrombosed
transverse sinus.

49. Variants of normal venous anatomy that
may mimic sinus thrombosis have been well
described
These can be subdivided into venous anatomic
variants that mimic occlusion (sinus atresia or
hypoplasia), asymmetric or variant sinus
drainage (occipital sinuses, sinus
duplication),and normal sinus filling defects
(arachnoid granulations, intrasinus septa).

50. Hypoplastic transverse sinus
The transverse sinuses are commonly
asymmetric, with the right transverse sinus
being dominant in the majority of cases. A
unilateral atretic posteromedial segment of the
left transverse sinus is also common

51. On the left a case that
demonstrates that you
cannot fully rely on phase
contrast imaging.
The signal in the vein
depends on the velocity of
the flowing blood and the
velocity encoding by the
technician.
On the far left a patient with
non visualization of the left
transverse sinus.
This could be
hypoplasia, venous
thrombosis or slow flow.
On the contrast enhanced
T1-weighted image it is
obvious that the sinus fills
with contrast and is patent.

52. Flow gaps most commonly appear in the
nondominant transverse sinus and are correlated with
a normal but small sinus as depicted at conventional
angiography. The combination of a small sinus size, a
slow or complex flow pattern, and an image
acquisition plane that is not perpendicular to the
sinus likely results in this finding . A close
assessment of the source images is mandatory to
accurately evaluate venous structures and reduce the
potential for diagnostic error. The lack of a thrombus
signal within the sinus on MR images is a helpful clue
for avoiding this pitfall. Flow gaps are a much less
common problem with the use of contrast-enhanced
MR venographic or CT venographic techniques

53. 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
(arrows).
(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).

54. 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. A close evaluation
of MR venographic source images usually allows
differentiation, as the thrombus signal is typically
not as intense as the flow related signal.
T1-weighted MR images in such cases depict an
abnormal increase in signal intensity within the
sinus.

55. 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).

56. Flow void on contrast-enhanced MR
On the contrast enhanced
T1 images on the left there is an
area of low signal intensity
within the enhancing transverse
sinus.
This could easily been mistaken
for a central thrombus within
the sinus.
This however is the result of
flow void.
On the phase contrast images it
is obvious that the transverse
sinus is patent.

57. We can conclude that MRI has many false positives
and negatives in the diagnosis of venous thrombosis.
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

58. Cerebral venous thrombosis is a relatively uncommon
but serious neurologic disorder.
Imaging plays a primary role in diagnosis. Prompt and
appropriate medical therapy is important because
brain parenchymal alterations and venous thrombus
formation are potentially reversible. MR imaging,
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.