Dural sinus thrombosis

Neuro-radiology

Neuroradiology(1991) 33:165-167

9 Springer-Verlag1991

Case Reports Dural sinus thrombosis Diagnosis and follow-up by magnetic resonance angiography and imaging T. S. Padayachee, J. B. Bingham, M. J. Graves, A. C. F. Colchester, and T. C. S. Cox Division of RadiologicalSciences,UMDS, London,UK Received: 9 April 1990

Summary. Magnetic resonance imaging has been reported to have advantages over conventional angiography in the diagnosis of dural sinus thrombosis. A case report is presented describing the application of MR techniques including MR angiography, to diagnose and monitor therapy for dural sinus thrombosis.

echoes instead of the usual signal void. Complications such as infarction, both haemorraghic and non-haemorraghic, are readily shown. A case report is presented describing the application of MR techniques including MR angiography, to diagnose and monitor therapy for dural sinus thrombosis.

Key words: Dural sinus thrombosis - Magnetic resonance imaging - Angiography

Case report

Thrombosis of a dural sinus may be encountered with no obvious underlying cause but may be precipitated by mastoid infection, dehydration, trauma, use of oral contraceptive and may be a consequence of a neoplasm. A number of haematological disorders such as polycythaemia, sickle cell anaemia and leukemia may also be predisposing factors. Symptoms of this condition are frequently non-specific, often related to raised intracranial pressure and include lethargy, headaches, sickness, transient weakness and disturbances of vision. The morbidity and mortality are high particularly in the presence of cerebral infarction. Diagnosis may be made by computed tomography (CT) but a high index of suspicion is necessary as the findings may be subtle. Abnormalities identified include the so called "empty" delta sign following enhancement [1-3] and haemorraghic venous infarction. The former is thought to arise from congestion of dural vascular collateral channels surrounding thrombus in the sinus [2]. Thin sections and coronal reformatting may be necessary to make the diagnosis. The configuration of the cisterna magna may mimic thrombus at the torcula and both arachnoid cysts and epidural abscesses may simulate this finding. The CT diagnosis is dependent on the density of the contrast bolus and scanning during the vascular phase [4-5]. Magnetic resonance (MR) imaging has been reported to have advantages over conventional angiography in the diagnosis of dural sinus thrombosis and has been advocated as the investigation of first choice for definitive diagnosis of dural sinus thrombosis [6-10]. High intensity signal is seen from thrombus within the dural sinus on all

A 28-year-old female presented with persistant severe frontal and lower occipital headaches associated with vomiting as well as paraesthesiae in the left hand. There was bilateral papilloedema, a left homonymous hemianopia and some left arm weakness. A C T scan was performed which showed small undisplaced ventricles with a low attenuation region in the right temporoparietal region and an empty delta/triangle sign suggesting sagittal sinus thrombosis. MR imaging was subsequently performed using a clinical imaging system (Philips Gyroscan, 1.5 Tesla with 10 m T . m -1 gradients). Transaxial T2-weighted images were obtained using a repetition time of 2,000 ms, echo times of 30,80 ms and two signal averages. The section thickness was 112 mm consisting of 14 contiguous 8 mm slices. A wedge shaped area of altered signal intensity was detected in ~the temporo-parietal region on the right with no associated mass effect (Fig. 1 a) and increased signal in the sagittal and right transverse sinuses consistent with thrombus formation. Increased signal was also noted in the right mastoid region (Fig. lb) which was attributed to mild inflammatory disease of the mastoid, though clinically no mastoid disease was detectable. At the same examination, MR angiograms were obtained using an Inflow method [11] which relies on the flow-related enhancement obtained with short repetition time, velocity compensated, field-echo pulse sequences to provide high contrast between moving blood and stationary tissue. A stack of 40, overlapping 2 mm slices (slice factor 0.7) was acquired in the sagittal plane using 2D acquisition. The repetition time was 39 ms, echo time 17 ms,

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Fig.la, b. Transaxial T2-weightedimages through the head showing: a infarction in the fight temporo-parietal region and thrombus in the superior sagittal sinus, and b inflammatory disease in the right mastoid Fig.2. Initial magnetic resonance angiogram in the sagittal plane, with absent flow in the sagittal and straight sinuses Fig.3 a, b. MR angiograms after 4 weeks of anticoagulation showing: a considerable return of blood flow to the venous sinuses, and b slight restriction of flow in the right transverse sinus

radiofrequency flip angle 45 ~and two signal averages were acquired. The angiographic projections of the data were then constructed by reformatting and applying a maximum intensity ray tracing algorithm (Analyze, BRU, Mayo Foundation, Rochester, USA). Multiple projections at different angles were combined to provide a cine sequence. Acquisitions in other planes were not possible due to time constraints imposed by the patient's condition. The M R angiogram clearly demonstrated no significant flow in the sagittal or straight sinuses (Fig. 2). A diagnosis of intracranial venous sinus thrombosis was made, associated with a right parietal infarct giving localising signs. The patient was treated with intravenous heparin and during the period of anticoagulation her headaches gradually reduced in frequency and severity. The focal signs improved and papilloedema showed early improvement. A C T scan performed 10 days later showed no evidence of haemorrhage and no increase in the size of the infarction. The M R T2-weighted images showed no change in the size of the infarct and the inflammatory mastoid disease remained. However, a signal void in the superior sagittal sinus indicated venous blood flow and there-

fore increasing patency of the dural sinuses. The MR angiogram showed a dramatic change from the first study with blood flow visualised in the sagittal, straight and transverse sinuses. An additional M R angiogram was obtained in the axial plane to visualise the transverse sinuses. Reduced, irregular signal was noted in the right transverse sinus indicating persistent thrombus and restricted blood flow. She was started on oral anticoagulation and a second follow-up M R study was performed 7 days later which showed similar T2-weighted images but the M R angiogram (Fig. 3 a) showed a marked increase in venous flow with visualisation of the cortical veins. An additional transaxial M R angiographic series however showed that there was still slight residual reduction of flow in the right transverse sinus (Fig. 3 b).

Discussion

The superiority of MR over CT in the detection of dural sinus thrombosis has been previously reported [7]. However, in acute thrombosis high field strengths can give rise

167 to decreased signal intensity which can be confused with patent dural sinuses [7]. Although the use of medium field strengths can overcome this problem, M R angiography provides conclusive visualisation of flow in the dural sinuses rather than relying on flow-related enhancement effects in imaging sequences [12]. The combined imaging and angiographic M R study provides sufficient information to obviate the need for conventional techniques with their associated hazards of ionising radiation, vessel puncture and intravenous contrast media. Applications of appropriate sequence parameters enables visualisation of venous flow alone whilst quantitative flow information may be obtained by use of additional pulse sequences [13]. The atraumatic nature of this imaging modality enables repeat studies to be performed, without risk, to evaluate the efficacy of medical treatment and resolution of the dural sinus thrombosis. We suggest that this combined M R study is advantageous compared to conventional imaging modalities and should become the imaging technique of choice for assessing dural sinus thrombosis.

Acknowledgements. We gratefully acknowledge the assistance of Mrs R E. Graves, Miss M. Tarnawski and Dr M. G. Taylor.

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T. S. Padayachee, Ph.D. Division of Radiological Sciences UMDS, Guy's Compus 3rd Floor Guy's Tower St. Thomas's Street London SE1 9RT UK