In neonates shock and dehydration is a common cause of venous thrombosis. In older children it is often local infection, such as mastoiditis, or coagulopathy.In adults, coagulopathies is the cause in 70% and infection is the cause in 10% of cases.In women, oral contraceptive use and pregnancy are strong risk factors.
The clinical manifestations of cerebral venous thrombosis vary, depending on the extent, location, and acuity of the venous thrombotic process as well as the adequacy of venous collateral circulation. Generalized neurologic symptoms (eg,headache, experienced by 75%–95% of patients) and focal neurologic deficits, including seizure, may result. Focal neurologic symptoms are more often seen in patients with parenchymal changes observed at imaging than in those without such changes.
The intracranial venous system may exhibit a wide range of normal variations According to traditional descriptions, the cerebral venous system consists of the deep venous system, superficial venous system, and dural venous sinuses (with their superior and inferiorcomponents) (18). The dural venous sinuses are enclosed in the leaves of the dura and serve as the major drainage pathway of the cerebral veins . The superficial veins of the cerebrum empty into the dural sinuses and are variable in morphologic structure and location. Superiorly draining (ascending) superficial veins are named for the area of cortex that they drain . Inferiorly draining (descending) superficial veins include the Labbe´ vein and the sylvian (superficial middle cerebral) veins The deep system includes the vein of Galen, the internal cerebral veins, and their tributaries; the Rosenthal vein (basal vein) and its tributaries; and the medullary and subependymal veins, which drain the hemispheric white matter
MIP image from contrast-enhanced MR venography, with a color overlay, demonstrates the superiordural 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). Theinternal jugular veins and bulbs (light purple) also are depicted. (2) Lateral MIP image from contrast-enhanced MRvenography, with editing of the deep veins to improve the visibility of the ascending veins that drain into the superiorsagittal sinus from the lateral hemispheric cortex (the frontopolar , anterior frontal , and posterior frontal veins; Trolard vein [superior anastomotic vein] ; and anterior parietal veins ) and the larger named veins on thelateral surface of the cerebrum (the superficial sylvian vein [superficial middle cerebral vein] , which typicallydrains into the sphenoparietal sinus or the cavernous sinus, and the Labbe´ vein , which drains into the transversesinus). The relative luminal diameters of the Trolard vein, Labbe´ vein, and superficial sylvian veins are reciprocal.
Venous thrombosis with absence of normal flow void on T1-weighted image.
CEREBRAL VENOUS THROMBOSIS
DEPARTMENT OF RADIO DIAGNOSIS Dr.NIJALINGAPPA PG IN RADIOLOGY DEPARTMENT OF RADIO DIAGNOSIS JJMMC DAVANGERE
The syndrome of intracranialvenous and sinus thrombosis -termed as cerebral venousthrombosis(CVT)
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
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%
One sinus only 23% Superior sagittal sinus 13% Lateral sinus 9% Straight sinus 1% Deep veins only 1% Isolated cortical veins 1%
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%)
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%
Thrombosis and endogenousthrombolysis and recanalization may occurconcurrently, the clinical manifestationsmay fluctuate in as many as 70% ofpatients, adding to clinical uncertainty. Intracranial hypertension occursin 20%–40% of patients with cerebralvenous thrombosis and should beexcluded in patients with the specificcomplex of symptoms
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 territories2. Thrombosis of major sinuses obstruction leads to impaired absorption of CSF and intracranial hypertension1/5 of patients with sinus thrombosis have intracranial hypertension only without signs of cortical vein thrombosis
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 ofRosenthal (BVR), vein of Galen (VOG), and straight sinus (StrS). On the volume-renderedimage, note the asymmetric appearance of the torcular herophili (TH), which is formed bythe 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 middlecerebral vein (SMCV). (c) Sagittal MIP CT image shows the inferior sagittal sinus (ISS), aswell as the internal cerebral vein, superior sagittal sinus, straight sinus, and vein of Galen.
Normal sinovenous anatomy. Three- Normal sinovenous anatomy.dimensional integral image from CT Axial MIP CT image showsvenography (lateral view) shows the asymmetric transverse sinus(TS).anastomotic vein of Trolard (AVOT) The sigmoid sinuses (SS) begindraining 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).
MIP image from contrast-enhanced MR venography, with a color overlay, demonstrates the superiordural sinuses. They include the superior sagittal sinus (green), inferior sagittal sinus (lightblue), straight sinus(dark purple), confluence of the sinuses (orange), transverse sinuses (darkblue), and sigmoid sinuses (yellow). The internal jugular veins and bulbs (light purple) also aredepicted. (2)lateral MIP image from contrast-enhanced MR venography, with editing of the deep veinsto improve the visibility of the ascending veins that drain into the superior sagittal sinus from thelateral hemispheric cortex (the frontopolar , anterior frontal , and posterior frontal veins;Trolard vein [superior anastomotic vein] ; and anterior parietal veins ) and the larger named veinson thelateral surface of the cerebrum (the superficial sylvian vein [superficial middle cerebral vein] , whichtypically drains into the sphenoparietal sinus or the cavernous sinus, and the Labbe´ vein , whichdrains into the transverse sinus).
Axial MR image series with a coloroverlay represents the majorsuperficial cortical venous drainageterritories according to Meder et al.Most of the superior cerebrum(green) is drained primarily into thesuperior sagittal sinus,which also receives drainage fromthe parasagittal cortical regions atlower levels.The sylvian veins drain blood fromthe peri-insular region (yellow) intothe basal dural sinuses.The transverse sinuses receiveblood from the temporal, parietal,and occipital lobes (blue).The Labbe´ vein, if dominant,maydrain much of this territory.Parenchymal abnormalities such ashemorrhage or edema in thisterritory may be indicative ofthrombosis of the transverse sinusor Labbe´ vein.
Direct visualization of a clot inthe cerebral veins on a nonenhanced CT scan is known asthe dense clot sign.It is seen in only one third ofcases.Normally veins are slightlydenser than brain tissue and insome cases it is difficult to saywhether the vein is normal or toodense .In these cases a contrastenhanced scan is necessary tosolve this problem
On the leftimages of apatient with ahemorrhagicinfarction inthe temporallobe (redarrow).Notice thedensetransversesinus due tothrombosis(blue arrows).
Thrombosis of the left transverse sinus in a 42-year-old woman. (a, b) Axialunenhanced CT images show left cerebellar and temporal hematoma withincreased attenuation in the left transverse sinus (cord sign) (* in a). (c) On a3D MIP image from CT venography, the left transverse sinus is not visible.
The empty delta sign is a finding that is seen on a contrast enhancedCT (CECT) and was first described in thrombosis of the superiorsagittal sinus.The empty delta sign is seen in 25%–75%The sign consists of a triangular area of enhancement with arelatively low-attenuating center, which is the thrombosed sinus.The likely explanation is enhancement of the rich dural venouscollateral circulation surrounding the thrombosed sinus, producingthe central region of low attenuation.In early thrombosis the empty delta sign may be absent and you willhave to rely on non-visualization of the thrombosed vein on theCECT.The empty delta sign can disappear in chronic stages withenhancement of organized clot or due to recanalization within thethrombus
Two cases of empty delta sign due to thrombosis of thesuperior sagittal sinus.
On the left a caseof thrombosis ofthe righttransverse sinusand the lefttransverse andsigmoid sinus(arrows).There isenhancementsurrounding thethrombosedhypoattenuatingveins
On spin-echo images patent cerebral veinsusually will demonstrate low signal intensity dueto flow void. Flow voids are best seen on T2-weighted andFLAIR images, but can sometimes also be seenon T1-weighted images.A thrombus will manifest as absence of flow void. Although this is not a completely reliablesign, it is often one of the first things, that makeyou think of the possibility of venousthrombosis. The next step has to be a contrast enhancedstudy
On the left a T2-weighted imagewith normal flowvoid in the rightsigmoid sinusand jugular vein(blue arrow).On the left thereis abnormal highsignal as a resultof thrombosis(red arrow).
The images on the leftshow abnormal high signalon the T1-weighted imagesdue to thrombosis.The thrombosis extendsfrom the deep cerebralveins and straight sinus tothe transverse and sigmoidsinus on the right.Notice the normal flow voidin the left transverse sinuson the right lower image.Absence of normal flowvoid on MR-images can bevery helpful in detectingvenous thrombosis, butthere are some pitfalls .Slow flow can occur inveins and cause T1hyperintensity.
The other sign that can help you in making the diagnosisof unsuspected venous thrombosis is venous infarction. Venous thrombosis leads to a high venous pressurewhich first results in vasogenic edema in the white matter ofthe affected area. When the process continues it may lead to infarction anddevelopment of cytotoxic edema next to the vasogenicedema. This is unlike in an arterial infarction in which there isonly cytotoxic edema and no vasogenic edema. Due to the high venous pressure hemorrhage is seenmore frequently in venous infarction compared to arterialinfarction. Since we are not that familiar with venous infarctions, weoften think of them as infarctions in an atypical location or ina non-arterial distribution.
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.
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
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.
Another typical venous infarctionis due to thrombosis of the veinof Labbé.On the left images demonstratinghypodensity in the white matterand less pronounced in the graymatter of the left temporal lobe..Notice that there is some lineardensity within the infarcted area.This is due to hemorrhage.In the differential diagnosis wealso should include a venousinfarct in the territory of the veinof Labbe.The subtle density in the area ofthe left transverse sinus (arrow) isthe key to the diagnosis.This is a direct sign of thrombosisand the next step is a CECT,
On the left images of apatient with hemorrhagein the temporal lobe.When the hemorrhagiccomponent of theinfarction is large, it maylook like any otherintracerebral hematomawith surroundingvasogenic edema. The clue to thediagnosis in this case isseen on the contrastenhanced image, whichdemonstrates the fillingdefect in the sigmoidsinus (blue arrow).
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
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
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
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 dont 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.
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.
Transverse MIP image of a Phase-Contrast angiography.The right transverse sinus and jugular vein have no signal due to thrombosis.
Acute thrombus in a 35-year-old woman with a severe headachefor 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).
Angiography is only performed in severe cases, when anintervention 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).
Arachnoid granulations Arachnoid granulations of Pacchioni play a major role in theresorption of cerebrospinal fluid. They are most commonly foundwithin the lacunae laterales of the superior sagittal sinus Arachnoid granulations can also protrude directly into thesinus lumen, adjacent to venous entrance sites, and should notbe mistaken for sinus thrombosis. Arachnoid granulations arepresent in the superior sagittal sinus, transversesinus, cavernous sinus, superior petrosal sinus, and straightsinus in decreasing order of frequency Arachnoid granulations produce well-defined focal fillingdefects within the dural venous sinuses and measure 2–9 mm indiameter. They are isoattenuating (one-third) or hypoattenuating(two-thirds) relative to brain parenchyma
Arachnoid granulationsof Pacchioni in thevenous sinuses. (a)Sagittal 2D MIP imagefrom CT venographyshow arachnoidgranulations (arrows) inthe superior sagittalsinus and straight sinus.(b) Axial contrast-enhanced CT imageshows a well-limitedlobulateddefect (arrow) in theright transverse sinus.
Classic appearance ofarachnoid granulations.(a) Photograph from ananatomic dissection ofthe right transverse sinusdemonstrates focalprotuberances consistentwith arachnoid granulations(arrows). Intrasinus septa(chordae willisii)(arrowheads)also are depicted.(b, c) Axial contrast-enhanced CT image (b)andsuperoinferior MIP imagefrom contrast-enhanced MRvenography (c) show well-defined focal filling defectsconsistent with arachnoidgranulations in the lateralpart of the transverse sinus(arrow), the most commonsite of such findings.
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
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.
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).
Wrong bolus timingThree images of a patient with venous thrombosis in the superiorsagittal 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 thecontrast injection.There is arterial enhancement and it looks as if the superior sagittalsinus enhances, but in fact what we see is the shine through of thedense thrombus.Only on the image on the right, which was made 45 seconds aftercontrast injection there is an empty delta sign, which proves thepresence of a thrombus in the sinus.
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.
Variants of normal venous anatomy thatmay mimic sinus thrombosis have been welldescribedThese can be subdivided into venous anatomicvariants that mimic occlusion (sinus atresia orhypoplasia), asymmetric or variant sinusdrainage (occipital sinuses, sinusduplication),and normal sinus filling defects(arachnoid granulations, intrasinus septa).
Hypoplastic transverse sinus The transverse sinuses are commonlyasymmetric, with the right transverse sinusbeing dominant in the majority of cases. Aunilateral atretic posteromedial segment of theleft transverse sinus is also common
On the left a case thatdemonstrates that youcannot fully rely on phasecontrast imaging.The signal in the veindepends on the velocity ofthe flowing blood and thevelocity encoding by thetechnician.On the far left a patient withnon visualization of the lefttransverse sinus.This could behypoplasia, venousthrombosis or slow flow.On the contrast enhancedT1-weighted image it isobvious that the sinus fillswith contrast and is patent.
Flow gaps most commonly appear in thenondominant transverse sinus and are correlated witha normal but small sinus as depicted at conventionalangiography. The combination of a small sinus size, aslow or complex flow pattern, and an imageacquisition plane that is not perpendicular to thesinus likely results in this finding . A closeassessment of the source images is mandatory toaccurately evaluate venous structures and reduce thepotential for diagnostic error. The lack of a thrombussignal within the sinus on MR images is a helpful cluefor avoiding this pitfall. Flow gaps are a much lesscommon problem with the use of contrast-enhancedMR venographic or CT venographic techniques
Transverse sinus flow gap. (a) Coronal image from TOF MR venographyshows 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 enhancementindicative of normal flow in the medial part of the left transverse sinus (arrow).
An intrasinus thrombus in the subacute stagemay have markedly increased signal intensity onMR images that may be misinterpreted as evidenceof flow on TOF MR venograms. A close evaluationof MR venographic source images usually allowsdifferentiation, as the thrombus signal is typicallynot as intense as the flow related signal.T1-weighted MR images in such cases depict anabnormal increase in signal intensity within thesinus.
T1-shortening shine-through in a patient withthrombosis of thesuperior sagittal sinusand transverse sinuses.Lateral MIP image fromcoronal TOF MRvenography shows anarea of thrombosiswith a signal ofintermediate intensity(arrows) resembling thatof normal sinus flow butless intense than that inpatent cortical veins(arrowheads).
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.
We can conclude that MRI has many false positivesand negatives in the diagnosis of venous thrombosis.Contrast enhanced MR-venography is the most reliable MRtechnique. CT-venography is even more reliable, because itis easy and less sensitive to pitfalls
Cerebral venous thrombosis is a relatively uncommonbut serious neurologic disorder.Imaging plays a primary role in diagnosis. Prompt andappropriate medical therapy is important becausebrain parenchymal alterations and venous thrombusformation are potentially reversible. MR imaging,TOF MR venography, contrast-enhancedMR venography, and CT venography are themost useful techniques for diagnosis of this condition.Knowledge of normal venous variations andpotential pitfalls related to image interpretationare important for achieving an accurate diagnosis.