Thrombosis of the cerebral veins: A review
Among the causes of “stroke,” cerebral ischemia accounts for nearly 80-85% of all cases, intracerebral hemorrhage about 10-15%, and subarachnoid hemorrhage 5-10%. Cerebral venous sinus thrombosis (CVST) only numbers about 0.5% in most cohorts. But it is important to recognize because it is very often missed and can lead to significant neurological deterioration if not appropriately and quickly managed. In this week’s BrainWaves podcast, Ali Hamedani turns the tables on me. Instead of me getting to ask him the questions, this time he conducts the interview.
Terminology. Ali asked me to distinguish what is meant by cortical vein and dural sinus thrombosis. And this is an important distinction to make when you suspect a patient of having a cerebral venous occlusion. I’ll refer the reader to the NEJM review by Stam from 2005 here, but to summarize it briefly, I’ll say that a cerebral vein thrombosis produces more local neurologic deficits whereas a dural sinus thrombosis can produce local deficits but also causes global cerebral dysfunction due to rapidly progressive intracranial hypertension. A cortical vein thrombosis can cause local vasogenic edema, followed by cytotoxic edema and venous infarction—which, if untreated, can also lead to intracerebral hemorrhage. Patients often complain of focal neurologic deficits, and on examination these may not localize to a single arterial distribution. For instance arm and leg numbness without weakness, or bilateral leg weakness would not commonly fit with an arterial cerebral infarction. The second location of venous injury would be an occlusion of the larger dural sinuses, which are responsible for the outflow of CSF from the arachnoid granulations. Whereas a cerebral vein thrombosis causes local injury, a dural sinus thrombosis may cause no local injury but will block drainage of reabsorbed CSF leading to a rise in intracranial pressure. In this situation, the ventricles will not dilate, and there may be no neuroimaging evidence of infarct or hemorrhage.
Who is at risk? Epidemiology studies have shown that a precipitating factor is recognized in 85% of cases. But this means 1 in 7 patients won’t have a history to raise your suspicion for a CVST. Obviously a patient with a history of hypercoagulability (known cancer, prior venous thromboembolism, family history, oral contraception) would be a concern. But you should consider Virchow’s triad and consider other subtle risk factors:
- Vaginal ring (higher risk of CVST than oral contraceptives)
- Tobacco use (causes endothelial injury)
- Nephrotic syndrome
- Inflammatory Bowel Disease
- Head injury (including lumbar puncture)
- Meningitis or sepsis
Neuroimaging features. As always, your first neuroimaging study in an adult patient with a new acute focal neurologic deficit that localizes to the central nervous system, with or without headache, with or without seizure, that first image will be a non-contrast CT scan. It’s a basic neurologic principle, but you need to get this image as soon as possible in order to rule out an intracerebral hemorrhage. On your non-contrast CT, there can be absolutely nothing abnormal—especially in the case of an acute dural sinus thrombosis when symptoms are only attributable to intracranial hypertension. There can be abnormal patterns of cytotoxic and vasogenic edema from venous infarction, and sometimes these vasogenic patterns can fluctuate or even move depending on the location and propagation of the venous occlusion. In rare cases, you can even see a “cord sign” which is the venous equivalent to the hyperdense MCA or hyperdense basilar artery in an acute arterial thrombosis. There can be focal or multifocal intraparenchymal hemorrhage, which is often disproportionate to the surrounding edema (often much more early edema). There can also be subdural and subarachnoid extension of the hemorrhage as well, which might confuse you for an underlying vascular malformation. To confirm a CVST, dedicated venous imaging is often obtained, either via CT venogram or MR venogram. These studies have comparable efficacy, but risks of contrast and radiation should be weighed in conjunction with accessibility and timing when selecting the study. The “empty delta” sign is a classic finding when the thrombosis involves the confluence of the sinuses in the occipital region, but any filling defect should be identified.
Management. Early anticoagulation has been strongly recommended by experts, even in the presence of intracerebral hemorrhage, according to American Heart Association Guidelines. This is the principal method for relieving venous obstruction and preventing propagation of thrombosis. In refractory cases, mechanical intervention (with thrombectomy) may be considered. In patients with dural sinus thrombosis and intracranial hypertension, osmotic therapy (e.g., mannitol or hypertonic saline) or diuresis (furosemide or acetazolamide) have been attempted with some success. In patients with severe venous infarctions or hemorrhage, decompression may relieve intracranial pressure by allowing the brain to swell. Neurosurgery should be consulted for each of these cases in order to coordinate the most optimal management. For secondary symptoms, these are typically managed pharmacologically. E.g., for seizures, experts recommend anti-epileptic therapy for a minimum of 6 months, however AEDs should not be initiated prophylactically. Headache due to intracranial hypertension is managed by relieving the venous obstruction (anticoagulation), but refractory head pain can be managed with over-the-counter non-steroidals, and sometimes adjunctive therapies like metoclopramide and vitamin supplements can be helpful. Patients with new neurologic deficits should be evaluated and supported with physical and occupational therapy, and neurologic follow-up as an outpatient—with or without repeat intracranial venous imaging—is important to assist in the ongoing care of these patients.
As usual, the BrainWaves podcast and online content are intended for medical education and entertainment purposes only. If you are looking for formal guidelines on the management of CVST, please read your institutional guidelines or this statement from the American Heart Association.
- Stam J. Thrombosis of the cerebral veins and sinuses. The New England journal of medicine. 2005;352:1791-8.
- Khandelwal N, Agarwal A, Kochhar R, Bapuraj JR, Singh P, Prabhakar S and Suri S. Comparison of CT venography with MR venography in cerebral sinovenous thrombosis. AJR Am J Roentgenol. 2006;187:1637-43.
- Ferro JM, Canhao P, Bousser MG, Stam J, Barinagarrementeria F and Investigators I. Early seizures in cerebral vein and dural sinus thrombosis: risk factors and role of antiepileptics. Stroke; a journal of cerebral circulation. 2008;39:1152-8.
- Saposnik G, Barinagarrementeria F, Brown RD, Jr., Bushnell CD, Cucchiara B, Cushman M, deVeber G, Ferro JM, Tsai FY, American Heart Association Stroke C, the Council on E and Prevention. Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke; a journal of cerebral circulation. 2011;42:1158-92.