Some minimal flow signal intensity was seen surrounding the thrombus (arrowhead, C), likely related to collateral flow within dural cavernous spaces or peripherally within the sinus. CONCLUSION. Nonetheless, in some cases, the determination of DST using spin-echo techniques (i.e., without MR venography) can be difficult. CE-MRV (relative to TOF-MRV) more accurately depicts recanalized channel morphology and produces a clearer picture of the degree of patency of thrombosed segments. Nevertheless, in some cases, the discrepant size of the transverse sinuses could be misinterpreted as thrombosis, particularly in light of the fact that MRI may underrepresent the size of a vessel lumen and may cause a small venous sinus or a sinus with slow flow to appear absent. Dural venous sinus thrombosis is a rare yet major cause of stroke and mortality, especially affecting young women and children. The thrombosed segments enhance intensely and can demonstrate internal flow voids, best seen on T2WI. A hypoplastic transverse or sigmoid sinus is often associated with alternative venous outflow pathways such as a persistent occipital sinus and mastoid emissary veins [22] (Fig. Cavernous Sinus Sinus Thrombosis Superior Sagittal Sinus Dural Sinus Cortical Vein These keywords were added by machine and not by the authors. In 1 patient, the duration of symptoms was not obtainable from the medical record. 7A, 7B, and 7C). The presence of the empty delta sign on contrast material-enhanced computed tomographic (CT) scans of the brain is considered pathognomonic of sagittal sinus thrombosis (SST); however, a valid explanation for its appearance is lacking, despite several hypotheses. The morphology of the thrombosed segments does not change on follow-up imaging. The purpose of this article is to bring some of the potential causes of false-positive and false-negative interpretations of dural sinus thrombosis (DST) on cross-section imaging studies to the attention of radiologists. OBJECTIVE. Six patients were imaged with both TOF-MRV and CE-MRV, and 3 were imaged by TOF-MRV only. The cases were selected in part by imaging criteria, though clinical exclusion criteria were also used. 4A and 4B). On unenhanced CT, one of the major findings of DST is that of a hyperdense sinus. Most (27/32, 84.4%) enhanced to an equal or greater degree than the same adjacent or contralateral dural sinus segments, shown to be normal on MR venography (Table 2). Type I. This prevented hypoplastic but normal sinus segments from being incorrectly categorized as thrombosed. Evolution of acute thrombosis: 43-year-old woman (patient 4) presented for imaging 2 days after onset of severe headache (A–C). This treatment was once controversial because the use of anticoagulants to promote blood flow was thought to exacerbate the cerebral hemorrhaging associated with the disease. Another confounding factor is the presence of hypointense thrombus on T2-weighted images simulating a flow void; in one study, this finding was found in approximately 10% of the cases of DST [12]. Introduction Dural sinus thrombosis (DST) is a disease entity in which early diagnosis can make an important difference with regards to patient outcome. Both axial and coronal TOF-MRV source images were assessed. Cerebral Venous Sinus Thrombosis Radiology. There were no prominent cortical veins, leptomeningeal vascular enhancement, or areas of persisting brain parenchymal signal intensity abnormalities. Nonetheless, because thrombus is occasionally hypodense on unenhanced CT, confusion with arachnoid granulations that are hypodense compared with blood can occur. More detailed MRV evaluation of each thrombosed segment was also performed on a separate workstation (Vitrea 2; Vital Images, Minnetonka, Minn). An occipital sinus has been reported to be present in 10% of normal brains on MR venography [19] (Fig. In many cases, false-negative interpretations of DST imaging studies are not due to misinterpretation of findings that clearly indicate abnormal flow. The inferior dural sinuses comprise the cavernous sinuses, which are connected through the anterior and posterior intercavernous sinuses, and the superior and inferior petrosal sinuses, which drain toward the sigmoid sinus and then toward the jugular bulb . This bright signal intensity probably relates to the vascularized connective tissue thrombus components or potentially slowly flowing oxygenated blood within small recanalized channels within the thrombus. Eventually, the thrombus is entirely replaced by vascularized connective tissue and converted to a fibrous mass, covered with endothelium, and traversed by endothelial lined channels.7 The endothelial lined channels, when large enough, probably correspond to recanalized channels visible as flow voids on T2-weighted sequences, flow-related signal intensity on TOF-MRV, and enhancing channels on CE-MRV. For instance, localizer images obtained using gradient-echo technique often show flow-related enhancement in dural sinuses (Figs. In 1 patient, thrombosis was identified on routine imaging follow-up after metastatic tumor resection. The prompt diagnosis of DST can be important in many cases and a false-positive diagnosis can cause a delay in establishing the correct diagnosis as well as lead to implementation of inappropriate therapy. Two cases were identified on follow-up of previously identified thrombosis. Hormonal changes, such as those caused by the oral contraceptive pill, pregnancy, steroids, or hypothyroidism 2. Copyright © 2013-2020, American Roentgen Ray Society, ARRS, All Rights Reserved. The empty delta sign: frequency and significance in 76 cases of dural sinus thrombosis. Standard maximum intensity projection (MIP) images were performed with right to left and anterior to posterior 180° rotations. Heterogeneity was related to hypoenhancing thrombus and intrinsic flow voids in each segment. Thrombosis of the cerebral dural venous sinuses, cortical draining veins, and deep cerebral veins is a rare clinical finding. Prognosis of cerebral vein and dural sinus thrombosis: results of the International Study on Cerebral Vein and Dural Sinus Thrombosis (ISCVT). The problem of a normal hyperdense appearance of the dural sinuses is also frequently encountered in infants and young children, in whom the relative density of the dural sinus compared with brain tissue is typically high for two reasons: first, a usually higher hematocrit value than in adults and, second, a typically lower brain density than in adults. Leach JL, Strub WM, Gaskill-Shipley, et al. On occasion, these structures can be elongated and can extend along the length of the dural sinus, simulating thrombus [17]. The filling defect is typically seen on multiple sections in contrast-enhanced CT and MR … Radiology 1987; 162:779-785 [Google Scholar] 5. On CE-MRV, 3 patterns were observed that correlated well with the TOF-MRV appearances. doi: 10.1161/01.STR.0000117571.76197.26 Link Google Scholar; 8. On T1-weighted images, acute thrombus may be isointense to brain and thus less conspicuous compared with subacute thrombus, which is hyperintense on T1-weighted images. The thrombus was hypointense on T2-weighting (arrows, A) and isointense on T1-weighted images, without enhancement (arrows, B). Flow voids were identified on parenchymal sequences (arrows in A–C) that correspond to recanalized channels on MRV techniques (arrows in D and E). The fact that arachnoid granulations are isointense with CSF (unlike thrombus) is a helpful distinguishing feature on MRI. Sinus thrombosis can be well imaged by both TOF-MRV and CE-MRV.9 TOF-MRV is a flow sensitive technique and many pitfalls associated with this technique are related to in-plane saturation or turbulent flow effects.9,13 CE-MRV is a more flow insensitive technique relying on vascular enhancement for vessel detection. To determine the frequency of the sign and its prognostic significance, 76 reported cases (112 CT manifestations) of SST and SST … Eight of 9 (89%) thrombosed lateral transverse sinus segments exhibited heterogeneous thrombus morphology. In the limited number of cases of chronic thrombosis described in the literature the internal signal intensity is typically isointense to hyperintense on T2WI and isointense on T1WI,4,8,9 although they can be variable.9 In this study, most (97%) of chronically thrombosed segments appeared markedly hyperintense relative to brain on T2WI. The imaging appearance in our cases may overlap with the appearance of dural arteriovenous fistula (DAVF),21 which is not surprising, given that the cause of many DAVFs may be episodes of prior dural sinus thrombosis.22 3D TOF-MRA was performed in 2 patients and did not demonstrate any evidence of fistula. 8). Arachnoid granulations have density that is isodense with CSF and are usually round. We sought to more fully characterize the imaging findings of this entity on MR imaging, time-of-flight MR venography (TOF-MRV), and elliptic centric-ordered contrast-enhanced MR venography (CE-MRV). An ongoing data base of cases of cerebral venous thrombosis was created in 2002, after Institutional Review Board approval. In the 8 segments that had no visible flow on TOF techniques, there was peripheral enhancement with clearly defined peripheral channels and central filling defects demonstrated on CE-MRV (Fig 3). However, in that study readers were specifically asked to examine unenhanced CT scans of patients with confirmed DST, which is a situation very different from a clinical environment in which the diagnosis is rarely previously known and, often, unanticipated. Follow-up imaging (scans used in evaluating the partially recanalized thrombosis) was performed 51 days after initial diagnosis (55 days after symptom onset) and 196 days after initial diagnosis (198 days after symptom onset). There are a lot of potential causes of dural venous sinus thrombosis, but the main risk factors include: 1. 2A and 2B). Anticoagulation is the mainstay of therapy; however, nearly 13% of the patients experience poor outcome with anticoagulation alone.1 In addition, nearly one thir … Thus, it is important that radiologists learn the clues that can be found on the requisition or in the electronic medical record that should raise suspicion of DST. No flow signal intensity was identified on TOF-MRV within the thrombosed left transverse and sigmoid sinuses (A). The thrombosed segments enhance intensely and can demonstrate internal flow voids, best seen on T2WI. The variable clinical and imaging follow-up is a limitation to this study, as is selection bias. TOF-MRV was performed in 9 patients (31 venous segments). The pathologic changes of chronic stage dural sinus thrombosis have been documented from 8 days to 6 weeks after symptom onset.7. False-negative causes of DST on CT venography are uncommon. CT of Dural Venous Sinus Thrombosis-- Non-contrast CT: – cord sign - cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain. 13A, 13B, 13C, and 13D). One patient of 51 with a lateral sinus thrombosis developed an asymptomatic dural arteriovenous fistula that was seen on follow-up angiography 12 months later. Dural venous sinuses are venous channels located intracranially between the two layers of dura mater. No treatment guidelines have been established based upon venous thrombus appearance on MR imaging. Recanalized channels were assessed on TOF-MRV by morphology (continuous or discontinuous) and location (peripheral or central) relative to the dural sinus margins. No patient in this study had contrast-enhanced CT imaging, CT venography, or angiographic evaluation because the diagnosis was clear based upon MR imaging. The additional 2 peripheral enhancement segments exhibited irregular discontinuous channels and central and peripheral continuous channel morphology on TOF-MRV. On that basis, it is important that the radiologist understand the relatively high rate at which obvious findings indicating DST are absent. Two patients were identified during follow-up of previously known acute venous thrombosis. Section thickness was 5.0 mm with an intersection gap of 1.0 mm. Section thickness and imaging parameters were the same as precontrast imaging. Radiographic features They are most commonly encountered in radiological practice as incidental osteolytic, sharply circumscribed indolent-appearing lucencies on skull CT or x-rays, or a filling defect in dural venous sinuses, which can be mistaken for dural venous thrombosis. A prospective, defined-interval, follow-up study of all cases of acute sinus thrombosis would be necessary to outline in more detail whether this appearance is characteristic for all cases of chronic thrombosis and is a goal of further research. Instead, misinterpretations are often due to lack of appropriate specific attention to the appearance of the dural sinuses. In the medical literature, this sign has been variably referred to as the “dense vein” sign [4], the “cord sign” [7], and the “triangle” sign [3]. Based upon our study, 3 major components of chronic partially recanalized thrombosed segments are proposed. Dural Venous Sinus Thrombosis Dr. Manmohan Bir Shrestha FOR RADIOLOGY 2. Small irregular recanalized channels were seen within the left transverse sinus (small arrows, B). MRV images were reformatted to match the exact image plane of the axial standard parenchymal images for detailed correlation. Nine patients underwent MR venography, all performed at 1.5T. Because thrombus can be hyperintense on unenhanced T1-weighted images, the signal produced by hyperintense thrombus can simulate flow within the dural sinus on TOF MR angiography and cause a false-negative finding (Figs. Areas of thrombus were seen as regions of signal intensity void on the MRV images (arrowheads, D and E). The overall venous morphology was better characterized on CE-MRV in each segment. Part of the difficulty in establishing the diagnosis of DST on MRI is that, in some circumstances, the signal intensity of the thrombosed sinus can simulate normal brain tissue or normal blood flow. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane such that it is visible on one image.