Cerebral Venous Thrombosis Workup

Lumbar puncture (LP) is helpful in evaluating for meningitis as an associated infectious process in cerebral venous thrombosis (CVT). However, a large, unilateral hemispheric lesion or posterior fossa lesion demonstrated on CT or MRI scan is a contraindication for LP.

In the past, compression of the jugular vein unilaterally with pressure measurement was utilized. Pressure may be elevated if thrombosis of the contralateral transverse sinus is present. However, collateral circulation or incomplete compression of the jugular vein may yield a false-negative result. Moreover, elevation of the intracranial venous pressure is a concern, as it may precipitate herniation. As the maneuver adds little to the diagnosis, it usually is not performed.

The diagnosis of cerebral venous thrombosis (CVT) is made on the basis of clinical presentation and imaging studies (see the images below), while clinical laboratory studies are useful for determining the possible causes of CVT.

Lab studies

A complete blood count (CBC) is performed to look for polycythemia as an etiologic factor. Decreased platelet count would support thrombotic thrombocytopenic purpura; leukocytosis might be seen in sepsis. (If heparin is used as treatment, platelet counts should be monitored for thrombocytopenia.)

Antiphospholipid and anticardiolipin antibodies should be obtained to evaluate for antiphospholipid syndrome. Other tests that may indicate hypercoagulable states include protein S, protein C, antithrombin III, lupus anticoagulant, and Leiden factor V mutation. These evaluations should not be made while the patient is on anticoagulant therapy.

Sickle cell preparation or hemoglobin electrophoresis should be obtained in individuals of African descent.

Erythrocyte sedimentation rate and antinuclear antibody studies should be performed to screen for systemic lupus erythematosus, Wegener granulomatosis, and temporal arteritis. If levels are elevated, further evaluation, including of complement levels, anti-deoxyribonucleic acid (DNA) antibodies, and neutrophil cytoplasmic antibodies (ANCA), could be considered.

Urine protein should be checked and, if elevated, nephrotic syndrome considered. Liver function studies should be performed to rule out cirrhosis.

EEG

An electroencephalogram (EEG) may be normal, show mild generalized slowing, or show focal abnormalities if a unilateral infarct occurs. An EEG is helpful in evaluating a seizure focus.

D-dimer values may be beneficial in screening patients who present in the emergency department for headache evaluation.

In a study of 18 patients with cerebral venous thrombosis (CVT), Tardy et al reported that D-dimer levels of less than 500 ng/mL had a negative predictive value for ruling out the diagnosis in patients with acute headache.^[17]

In a prospective study of 54 consecutive patients with headache suggestive of CVT, Lalive found that 12 had CVT and, of those, 10 had D-dimer levels greater than 500 ng/mL.^[18] The 2 patients with confirmed CVT and a D-dimer level of less than 500 ng/mL had a history of chronic headache lasting longer than 30 days.

In a study by Kosinski et al, D-dimers were positively correlated with the extent of thrombosis and negatively correlated with the duration of symptoms in patients with cerebral sinus thrombosis. The investigators prospectively studied 343 patients with symptoms suggesting cerebral sinus thrombosis.^[19] The diagnosis was confirmed in 35, with 34 of these patients showing elevated D-dimer levels greater than 500 mcg/L. Of the 308 patients not having CVT, 27 had positive values. Sensitivity was 97.1%, with a negative predictive value of 99.6%. Specificity was 91.2%, with a positive predictive value of 55.7%.

The D-dimer test does not establish the diagnosis of CVT, and more definitive studies, such as magnetic resonance venography (MRV), are necessary. Likewise, if a high suspicion for CVT exists, the test cannot definitely exclude the diagnosis but can indicate that the presence of CVT is very unlikely.

Computed tomography (CT) scanning is an important imaging technique, as it is often the first imaging study obtained. It may show evidence of infarction that does not correspond to an arterial distribution. However, in the absence of a hemorrhagic component, demonstration of the infarct may be delayed for as long as 48-72 hours. (See the image below.)

CT scanning is also useful for ruling out other conditions, such as neoplasm, and in evaluating coexistent lesions, such as subdural empyema. CT scanning of the sinuses is useful in evaluating sinusitis, while CT scanning of the mastoids may be helpful in lateral sinus thrombosis.

An empty delta sign appears on contrast scans as enhancement of the collateral veins in the superior sagittal sinus (SSS) walls surrounding a nonenhanced thrombus in the sinus. However, the sign is frequently absent. Early division of the SSS can give a false delta sign. The dense triangle sign formed by fresh coagulated blood in the SSS and the cord sign representing a thrombosed cortical vein are extremely rare.

CT angiography

CT angiography has also been used to visualize the cerebral venous system. Ozsvath et al compared CT and MR projection in the identification of cerebral veins and thrombosis.^[20] CT venography was superior to MR in identification of cerebral veins and dural sinuses. CT was equivalent to MR in identification of dural sinus thrombosis and therefore is a viable alternative to MRV in the examination of patients with suspected dural sinus thrombosis. The maximum-intensity-projection technique used, however, did not allow direct visualization of the thrombus by CT or MR technique.

MRI shows the pattern of an infarct that does not follow the distribution of an expected arterial occlusion. It may show absence of flow void in the normal venous channels. Mas et al described MRI findings of increased intraluminal signal on all planes and with all pulse sequences in patients with lateral sinus thrombosis. (See the image below.)^[21]

MRV

MRV is an excellent method of visualizing the dural venous sinuses and larger cerebral veins. (See the images below.)

Since thunderclap headaches are not limited to SAH and may be seen with cerebral venous thrombosis (CVT), lack of evidence of SAH in a patient with such headaches should prompt examination with MRV.

SSPCA

Single-slice phase-contrast angiography (SSPCA) takes less than 30 seconds and provides rapid and reliable information. Many neurologists now consider it to be the procedure of choice in diagnosing cerebral venous thrombosis. In a study of 21 patients, Adams demonstrated a specificity and sensitivity of 100% for SSPCA when compared with alternative imaging techniques.^[22]

Flow gap versus thrombosis in MRV

Ayanzen described transverse sinus flow gaps in 31% of patients with normal MRI findings who were studied with MRV; 90% of these were in the nondominant transverse sinus, and 10% were in the codominant sinuses. None was seen in the dominant sinus.^[23] These should not be mistaken for thrombosis.

Carotid arteriography with delayed filming technique to visualize the venous system was the procedure of choice in the diagnosis of venous thrombosis prior to the advent of MRV. It is an invasive procedure and is therefore associated with a small risk.

If MR studies are not diagnostic, conventional angiography should be considered. Direct venography can be performed by passing a catheter from the jugular vein into the transverse sinus, with injection outlining the venous sinuses.