Hypointense thrombus on T2-weighted MR imaging: a potential pitfall in the diagnosis of dural sinus thrombosis

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Abstract

Purpose: To determine the frequency of hypointense appearance of dural sinus thrombosis on T2-weighted images, which may mimic a normal flow void, and when possible correlate with appearance on T1-weighted images. Methods and Materials: Retrospective review of radiology files showed 51 patients with a discharge diagnosis of dural sinus thrombosis who underwent MR imaging during the period 1986–1998. These images were reviewed by an experienced neuroradiologist for appearance on T2-weighted images. This process yielded five cases in which a hypointense appearance on this pulse sequence simulated a normal flow void. An additional two cases were added from the teaching files of two other institutions giving a total of seven cases (13% of studies). The resulting study population consisted of five women and two men (mean age 27.1 years). T1 weighted images were available in five patients. In two patients MR venography was available, but not T1-weighted images. The diagnosis of dural sinus thrombosis was based solely on absence of flow void on T1-weighted images in one case, solely on absence of flow void on MR venography in two cases and absence of flow void on T1-weighted images in conjunction with MR venography or gradient echo findings in 4 patients. All images were obtained on a 1.5 T magnet (GE Medical Systems; Milwaukee, Wisconsin). Results: In all patients hypointense signal of thrombus was isointense with normal flow voids in other dural sinuses on T2-weighted images. In all cases in which T1-weighted images were available, the signal intensity of thrombus was isointense to gray matter. Conclusion: Hypointense appearance of thrombus on T2-weighted images is a potential pitfall in the MR diagnosis of dural sinus thrombosis. Because thrombus in this stage of evolution appears isointense to gray matter on T1-weighted images, careful attention must be paid to other sequences to avoid this pitfall.

Introduction

Dural sinus thrombosis (DST) is an entity characterized by thrombosis of one or more dural sinuses and often accompanied by nonspecific complaints of headache, visual disturbance and, on occasion, decreased level of consciousness. One important potential complication of dural sinus thrombosis is retrograde extension of thrombus into deep cerebral veins or adjacent cortical veins, which can result in venous infarction and is thought to account for 2% of strokes in young adults [1]. Treatment consists of systemic anticoagulation with heparin or, in advanced cases, direct endovascular therapy. Because the prognosis of untreated central venous thrombosis is grave [2], [3], prompt diagnosis is essential. Clinical features of dural sinus thrombosis are nonspecific, and imaging plays an important role in establishing the diagnosis. Consequently, the radiologist may be the first individual to suggest the diagnosis.

CT signs of dural sinus thrombosis may not always be present or may be difficult to identify due to technical factors, resulting in lower sensitivity [3], [4], [5]. Consequently, magnetic resonance (MR) imaging and MR venography are currently considered the imaging studies of choice for evaluation of dural sinus thrombosis because CT is an insensitive test[3], [4], [5]. Typical findings of dural sinus thrombosis on MR imaging are reported to be lack of flow void on spin echo images and absence of signal on magnetic resonance venography [3], [4]. However, diagnosis by MR is not without difficulty, as potential pitfalls have been suggested [3], [4], [5], [6]. One such pitfall consists of hypointense signal of acute thrombus on T2-weighted images, which may be mistaken for a normal flow void if attention is not paid to ancillary findings on other imaging sequences. We set out to determine the frequency of hypointense appearance of dural sinus thrombosis on T2-weighted images and possible correlate this finding with appearance on T1-weighted images.

Section snippets

Subjects and methods

Search of computer files by discharge diagnosis of patients seen at our institution during the period 1986–1998 showed 51 patients with a discharge diagnosis of dural sinus thrombosis, who had also undergone MR imaging. These cases were reviewed by a board certified neuroradiologist for appearance on T2-weighted MR images, which revealed five cases in which a hypointense appearance on this pulse sequence simulated a normal flow void. An additional two cases were added from the teaching files of

Results

In all patients, hypointense signal of thrombus in the dural sinuses mimicked a normal flow void on T2-weighted images. Locations of thrombus included solely the superior sagittal sinus in one case, solely transverse sinus in three cases (Fig. 1, Fig. 2), transverse sinus and superior sagittal sinus in one case, solely straight sinus in one case and superior sagittal sinus and the straight sinus in 1 case (Fig. 3). In all cases in which T1-weighted images were available, the signal intensity of

Discussion

Dural sinus thrombosis can result from a variety of conditions, including: intracranial infection, dehydration, compression by tumor, pregnancy and the puerperium, hypercoagulable states, oral contraceptives, polycythemia, sickle cell disease and trauma [2]. Patients often present with nonspecific signs and symptoms such as headaches, nausea and vomiting. In advanced cases, papilledema, seizures and diminished level of consciousness can be seen [2].

Radiologic diagnosis of dural sinus thrombosis

Conclusion

The signal of acute intraluminal thrombus on T1 and T2-weighted images results in a potential pitfall in MR imaging of dural sinus thrombosis. Appearance of thrombus on T2-weighted images, which mimicked a normal flow void, was encountered in 13.2% of cases images over a 12-year period. This finding was seen relatively frequently in our study, suggesting that it is likely commonly encountered in clinical practice.

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