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Brain, Venous Sinus Thrombosis Last Updated: July 28, 2005 |
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| Synonyms and related keywords: sinus thrombosis, venous infarcts, cerebral venous thrombosis |
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AUTHOR INFORMATION
| Section 1 of 12   |
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| Author: Mahesh R Patel, MD, Chief of MRI, Department of Radiology, Santa Clara Valley Medical Center |
| Mahesh R Patel, MD, is a member of the following medical societies:
Radiological Society of North America |
| Editor(s): Hugh J Robertson, MD, DMR, FRCPC, FRCR, FACR, Professor Emeritus, Department of Radiology, Section of Neuroradiology, Louisiana State University School of Medicine; Clinical Professor, Department of Radiology, Tulane University School of Medicine, Consulting Staff, Department of Radiology, University Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand;
Georges M Salamon, MD, Visiting Research Professor, Department of Radiology, David Geffen School of Medicine, University of California at Los Angeles;
Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute;
and James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences |
Disclosure
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INTRODUCTION
| Section 2 of 12   |
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Background: Cerebral venous thrombosis is an elusive diagnosis because of its nonspecific presentation and its numerous predisposing causes. It is more common than previously thought. Imaging plays a key role in the diagnosis.
Cerebral venous thrombosis often presents with hemorrhagic infarction in areas atypical for arterial vascular distribution. Magnetic resonance venography (MRV) in conjunction with conventional MRI can accurately diagnose cerebral venous thrombosis. With careful interpretation and a high degree of clinical suspicion, CT also may lead to the diagnosis. Pathophysiology: Cerebral venous thrombosis results from occlusion of a venous sinus and/or cortical vein and usually is caused by a partial thrombus or an extrinsic compression that subsequently progresses to complete occlusion. Once the vein is occluded, the thrombus may extend to veins draining into the sinus. This results in cortical venous infarction with petechial or overt hemorrhagic perivascular venous infarction.
Multiple pathophysiologic mechanisms and predisposing factors exist, including the following:
- A hypercoagulable state
- Extrinsic compression or local invasion of a venous by tumor or an adjacent infectious process (eg, mastoiditis)
- A low-flow state within the venous sinus
- Dehydration
- Pregnancy and the postpartum state
As many as 25% of patients present with no predisposing risk factor; however, in some patients, an etiologic factor is discovered subsequently.
When occlusion of a venous sinus occurs, the resulting venous congestion can lead to regional ischemia and infarction. Venous infarctions frequently are hemorrhagic and commonly occur within the white matter or at the gray-white matter junction. Involvement of the deep cerebral veins (eg, basal vein of Rosenthal) can progress to bilateral thrombosis of the internal cerebral veins with thalamic hemorrhagic infarction. Frequency:
- In the US: A range of occurrence in less than 1-9% of subjects has been suggested based on a limited autopsy series. The higher percentage may apply to older patients with concordant debilitating disease. Venous thrombosis is believed to be less common than arterial occlusive disease.
- Internationally: No current data are available. It is likely to be underdiagnosed since the availability of MR in developing countries is limited, and patients are not studied often by cerebral arteriography.
Mortality/Morbidity:
- A mortality range of 10-80% has been reported although the higher rate is based on older data.
- Recent studies estimate a morbidity range of 6-20%, including residual focal neurologic deficits and blindness secondary to optic nerve atrophy.
- The prognosis for return of function is believed to be somewhat better than for arterial stroke.
Age:
- Elderly or debilitated patients (eg, those with an underlying illness) are more likely to have spontaneous cerebral venous thrombosis.
- Neonates and infants suffering from dehydration may develop cerebral venous thrombosis.
Clinical Details: The signs and symptoms of cerebral venous thrombosis occasionally are nonspecific and protean, making the clinical diagnosis difficult.
- Patients may have generalized or focal neurologic symptoms and signs.
- Headaches
- Nausea
- Vomiting
- Possible seizures
- Occasionally venous thrombosis may be mistaken for a psychiatric disorder (neurosis, hysteria, depression)
- Physical examination findings may include the following:
- Papilledema may be seen.
- Forehead skin and eyelid edema, ocular chemosis, proptosis, and cranial nerve III, IV, and VI compromise can result from cavernous sinus thrombosis.
- An isolated cortical venous thrombosis can result in focal neurologic symptoms and signs (related to the anatomic location of the thrombosis).
- Predisposing factors include the following:
- Hypercoagulable states including the use of oral contraceptives
- Pregnancy and the postpartum period
- Local or distant infection, including mastoiditis, otitis media, paranasal sinus infection, generalized sepsis, and facial or scalp cellulitis
- Circulatory low-flow states resulting from blood volume depletion, dehydration, and/or cardiac disease
- Behçet syndrome
- Antiphospholipid antibody syndrome
- Factor V Leiden genetic mutation and other hereditary thrombotic conditions
- Arteriovenous malformations posttreatment
- Direct trauma
- Invasion of dural sinuses by adjacent tumor
- Numerous chronic illnesses with sepsis, dehydration
- In neonates and infants - Sepsis, dehydration, birth trauma, shock, and L-asparaginase therapy
- Dural arteriovenous fistulas - May develop after dural sinus thrombosis
- Intracranial hypotension - May occur in patients with extended thrombosis of the dural sinuses.
Preferred Examination: - MRI with MRV is preferred for diagnosis. Clinical manifestations and physical findings may be nonspecific.
- The diagnosis may be made or suggested by CT brain scan before and after intravenous contrast medium injection.
Limitations of Techniques: Two-dimensional time-of-flight (2D TOF) MRV is performed in the coronal plane; however, in-plane signal loss that mimics thrombosis may occur with this technique. Thus, a review of source data and conventional MRI brain scan is necessary. Phase-contrast MRV techniques may help since small cortical venous infarcts may not be observed on 2D TOF MRV.
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DIFFERENTIALS
| Section 3 of 12 |
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Brain, Capillary Telangiectasia
Brain, Contusion
Brain, Hypertensive Hemorrhage
Brain, MRI Appearance of Hemorrhage
Brain, Metastases
Brain, Stroke
Brain, Venous Vascular Malformations
Other Problems to be Considered:
Brain, vasculitis
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RADIOGRAPH
| Section 4 of 12 |
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Findings: Conventional skull radiography is not useful. No conventional radiographic findings are described. |
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Findings: The diagnosis occasionally can be made by CT scan with careful attention to the findings, which may be subtle (see Images 1-2 and Image 5). Diagnostic findings include the following:
- On noncontrast CT scan, the classic finding is the delta sign, which is observed as a dense triangle (from hyperdense thrombus) within the superior sagittal sinus. However, this is not specific, since high attenuation in the healthy nonthrombosed sinus can be observed occasionally and is common in neonates because of an elevated hematocrit.
- On contrast-enhanced CT scan, the reverse delta sign (ie, empty triangle sign) can be observed in the superior sagittal sinus from enhancement of the dural leaves surrounding the comparatively less dense thrombosed sinus.
- The presence of both the delta and reverse delta signs increases the likelihood of the diagnosis.
- On CT brain scan, infarctions in a nonarterial distribution in the white matter and/or cortical white matter junction, often associated with hemorrhage, should suggest the possible diagnosis of venous thrombosis. Bilateral cerebral involvement can occur, including the superior cerebral white matter of the convexities from superior sagittal sinus thrombosis, or the basal ganglia and thalami from internal cerebral vein thrombosis in which the internal cerebral veins appear hyperdense in the noncontrast scan.
- Indirect CT signs include focal cerebral cortical ischemia with gyral enhancement, small ventricles compressed by cerebral edema, and intense tentorial enhancement. Occasionally, the transcerebral medullary cortical veins can be observed.
Degree of Confidence: - The characteristic CT scan appearances and signs strongly suggest cerebral venous thrombosis but CT scans are seldom conclusively diagnostic. Because of the subtlety of the findings, the prospective diagnosis of venous thrombosis may not be made unless a high index of suspicion is maintained during interpretation of the CT study.
- CT venography also can confirm the diagnosis. It does not suffer from the in-plane flow artifact that causes signal loss on 2D TOF MRV.
- In most patients, MRI brain scan with MRV is recommended to establish the diagnosis. Cerebral arteriography and venography may be necessary when MRI scan and MRV are not available.
False Positives/Negatives: - A false-positive delta sign may occur in a trauma setting because of an adjacent subdural hematoma.
- The dural sinus normally may appear hyperdense relative to adjacent tissues. Both the delta and reverse delta signs may need to be present to establish the diagnosis.
- Occasionally, the superior sagittal sinus may bifurcate proximal to the torcular herophili, resulting in a confluens sinuum and an empty delta sign without the presence of a venous thrombosis.
Findings: MRI in conjunction with MRV is both sensitive and specific enough to provide the best noninvasive method of diagnosing cerebral venous thrombosis (see Images 3-4and Images 6-8). The diagnosis usually can be made without intravenous contrast although contrast enhancement can aid in confirming the diagnosis. MR imaging findings are as follows:
- A thrombus can be directly visualized within a vessel.
- Secondary venous infarctions and foci of hemorrhage can be seen with gradient-echo images. Susceptibility induced signal loss from deoxyhemoglobin provides a basis for detection of even small foci of hemorrhage, which tend to occur in the subcortical white matter, thalami, and basal ganglia.
- Dilated venous collaterals such as transcortical medullary veins provide indirect evidence of venous thrombosis. The appearance of intravenous thrombus on conventional MRI depends on the age of the blood clot within the vessel.
- In acute venous thrombosis, loss of flow void on T1-weighted images occurs along with hypointensity on T2-weighted images, making the determination of sinus occlusion difficult.
- In the subacute phase, blood clot can result in loss of normal flow void on T1-weighted images and T1 hyperintensity; conversely, on T2-weighted images blood clot can be of low signal intensity, thus mimicking flowing blood. In this instance, blood is in the intracellular methemoglobin stage. Flow-related enhancement phenomena created by slow flow can occur in veins and cause T1 hyperintensity.
- To circumvent this problem, flow-sensitive imaging techniques can be used (ie, 2D TOF or phase-contrast MRV) to accurately assess the venous sinuses; 2D TOF MRV pulse sequence is sensitive to slow flow. Maximum signal is produced when blood flows orthogonal to the imaging plane, and since many cerebral veins course in an anteroposterior direction, coronal acquisition is often used with an inferior saturation pulse to eliminate arterial signal.
- Restricted diffusion may or may not be seen in cerebral venous thrombosis and, when present, may occasionally be reversible.
Degree of Confidence: - Variants of venous anatomy are common, and a hypoplastic sinus or prominent arachnoid granulations may simulate venous sinus thrombosis.
- With 2D TOF MRV techniques, thrombus in the intracellular or extracellular methemoglobin stage can present with increased signal and falsely simulate blood flow.
- Phase-contrast MRV may avoid this error.
False Positives/Negatives: - Hypoplasia or severe attenuation of a transverse sinus, which are normal anatomic variants, may simulate venous sinus thrombosis.
- In-plane flow-induced signal loss in 2D TOF MRV also can mimic intravenous thrombus.
- Prominent arachnoid granulations may simulate thrombus. A careful review of the MRV images and conventional MRI may lead to the correct diagnosis.
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ULTRASOUND
| Section 7 of 12 |
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Findings: In general, ultrasonography is not useful except as follows:
- In neonates, the diagnosis of venous sinus thrombosis may be made by color Doppler ultrasound. An isolated case diagnosed with power Doppler was reported in the literature.
- A published series from Germany reported 14 patients with transverse sinus thrombosis studied by transcranial color duplex ultrasonography and concluded that without contrast media administration, ultrasonography is "almost useless."
- The use of Levovist imaging agent (ie, transpulmonary stable microbubbles formed in galactose suspension) results in a signal increase of 25 dB and offers improved diagnostic capability.
Degree of Confidence: Ultrasonography is not considered a good modality for evaluation of cerebral venous thrombosis; better noninvasive modalities include MRI with MRV and CT venography. False Positives/Negatives: Similar to other imaging modalities, differentiation of the normal anatomic variant of hypoplastic sinus from a thrombosed sinus can be difficult.
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NUCLEAR MEDICINE
| Section 8 of 12 |
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Findings: Nuclear medicine has no significant role in the evaluation of cerebral venous thrombosis; however, localized reduced perfusion in the affected venous distribution can be observed. Degree of Confidence: Radionuclide studies are of limited use; MR and CT venography are preferred. False Positives/Negatives: - Radionuclide study may result in a false-positive finding in partial thrombosis.
- Because of the low spatial resolution of the radionuclide study, collateral vessels adjacent to a thrombosed venous sinus may mimic a patent sinus.
- Congenital variations in venous anatomy (eg, unilateral transverse sinus) are not discernible from venous sinus occlusion.
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ANGIOGRAPHY
| Section 9 of 12 |
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Findings: Prior to the advent of MRI, the diagnosis was confirmed by contrast arteriography.
- Classic findings include the following:
- Filling defects from thrombus within the venous sinus
- Occlusion of a draining sinus
- Secondary indirect angiographic findings are as follows:
- Decreased focal venous circulation around a thrombosed venous sinus
- Visualization of collateral circulation
- Narrowing of arteries in the involved region
- Prolonged contrast blush in the brain parenchyma
- Tortuous vessels in the capillary and venous phases
- Collateral flow in dilated anastomotic vessels
Degree of Confidence: With classic findings the diagnosis is certain; however, several pitfalls exist.
- Prolonged venous circulation can arise from other etiologies (eg, local mass effect).
- A dural venous sinus can be congenitally hypoplastic or absent.
- Prominent arachnoid granulations at the junction of the vein of Galen and straight sinus may simulate thrombus. This is also a diagnostic problem with MR and CT venography.
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INTERVENTION
| Section 10 of 12 |
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Intervention: - Treatment of dural sinus thrombosis usually requires anticoagulant drugs. Some authors believe heparin is effective, since it saves brain tissue that may be reversibly damaged in venous thrombosis and is more effective than in the treatment of arterial cerebrovascular disease where the ischemic penumbra is smaller. In a series of 42 patients, 36 had partial or complete venous sinus recanalization following heparin therapy.
- Direct infusion of thrombolytic drugs into the thrombosed sinus using an endovascular microcatheter may result in sinus recanalization. This may be used for patients who deteriorate despite systemic anticoagulation therapy.
- Venous thrombosis may be associated with a subsequent dural arteriovenous fistula. There is a case report of endovascular recanalization of the left transverse and sigmoid sinuses and subsequent balloon angioplasty with stent placement via the left internal jugular vein.
- A 1-year follow-up report of 57 patients with sinus thrombosis revealed 8 deaths and 35% of remaining patients with cognitive impairment.
- In the rare patient who develops coma, fixed and dilated pupils, and brain herniation, early intervention by emergency decompressive craniectomy may be helpful.
Medical/Legal Pitfalls:
- Signs and symptoms of venous sinus thrombosis are somewhat nonspecific. A high degree of clinical suspicion and a comprehensive list of differential diagnoses can facilitate diagnosis.
- Dural venous sinus thrombosis can occur during pregnancy and the postpartum period. Include sinus thrombosis in the differential diagnosis of patients presenting with neurologic disorders and hypertensive encephalopathy.
- Third-generation oral contraceptives result in increased risk of cerebral venous sinus thrombosis and venous thromboembolism, although the risk is small (approximately 4 in 1 million). Patients with additional risk factors for venous thrombosis, such as hereditary clotting disorders or a strong family history, have an increased risk factor of 30. Such patients are advised not to use oral contraceptives.
- Venous sinus thrombosis was described in a young male body builder who used androgenic steroids. The thrombosis was believed to occur from platelet activation or from an increase in coagulation factors. Androgen use may be frequent and covert in athletes.
- Due to the widespread use of the recreational drug Ecstasy (3,4-methylenedioxymethamphetamine [MDMA]), patients may present with a variety of neurologic complications. A 22-year-old woman ingested a single tablet of Ectasy and danced for 8 hours without ingesting fluids. Subsequently, she developed cerebral venous thrombosis. Dehydration resulting from drug-induced heat production and excessive perspiration was a probable cause of the venous thrombosis.
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PICTURES
| Section 11 of 12 |
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| Caption: Picture 7. Axial MR venogram demonstrates occlusion of the left transverse sinus, sigmoid sinus, and internal jugular vein.
|  |  View Full Size Image |
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Picture Type: MRI |
| Caption: Picture 8. Sagittal T1-weighted image demonstrates T1-hyperintense thrombus (arrows) within the superior sagittal sinus consistent with thrombus. Courtesy of James G. Smirniotopoulos and MedPix.
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Picture Type: MRI |
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BIBLIOGRAPHY
| Section 12 of 12 |
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Brain, Venous Sinus Thrombosis excerpt |
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