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Neuroradiology Case of the Week

Case 53

Ravinder Sidhu MD, Lawrence Buadu, MD, PhD, Sven Ekholm MD, PhD,
and P-L Westesson MD, PhD, DDS

Clinical Presentation: An 8-year-old female with nephrotic syndrome presented with a one-day history of headache.

Radiological Findings: Axial and sagittal T1-weighted MR images revealed an iso to hypointense signal at inferior and posterior aspects of the left superior sagittal sinus, extending into transverse, sigmoid, and jugular sinus (Fig.1 A-C). Axial T2-weighted MR images show the lesion to be hypointense in nature, thereby suggestive of acute thrombus (Fig. 2). MR venography confirmed the thrombosis of transverse sinus with extension into superior sagittal, transverse, and sigmoid sinus (Fig. 3).

Diagnosis: Left transverse sinus thrombosis extending into superior sagittal, sigmoid and jugular sinus

Discussion:  

Clinical Discussion: The superior sagittal sinus is a midline venous channel located between the inner and outer dural laminae. It receives blood from many tributaries, including the cortical cerebral, meningeal, emissary, and scalp veins. These channels can provide a collateral pathway that bypasses the thrombosis of the superior sagittal sinus [1].
   Many predisposing factors have been implicated in the development of superior sagittal sinus thrombosis. Trauma, infection, tumors, dehydration, hypercoagulable states such as pregnancy, oral contraceptives and nephrotic syndrome are the most common causes. Unusual causes include Behcet disease, acquired immunodeficiency syndrome, ulcerative colitis, chemotherapy (particularly with asparginase and cytarabine), and the blastic crisis of chronic myelogenous leukemia, lupus and jugular vein catheterization. In addition, dural sinus thrombosis has also been associated with congenital heart disease, antiphospholipid syndrome. Nearly 20% of cases of dural sinus thrombosis are idiopathic [2]. Superior sagittal sinus thrombosis is an extremely rare complication of nephrotic syndrome and is associated with hypercoagulable state due to factors like elevated levels of plasma fibrinogen, and factors V, VII, VIII, X [3].
    Dural sinus thrombosis manifests with diverse clinical findings. Early symptoms include headaches and lethargy. As the disease progresses, seizures, decreased mentation, and focal deficits can occur. Strokes (hemorrhagic) may develop secondary to poor venous drainage. These strokes are often bilateral and outside the normal arterial distribution, reflecting the pattern of venous drainage.
    Veno-occlusive disease of the brain most commonly affects the superior sagittal sinus, followed by the transverse, sigmoid, and straight sinuses.

Imaging Discussion: Imaging findings can be grouped into those related to:

1. intraluminal thrombus (e.g. empty delta sign,”cord sign”),
2. venous collateral flow, (e.g. gyral and tentorial enhancement),
3. brain involvement (e.g. hemorrhage, infarcts, edema), and
4. changes in flow dynamics, which are most evident on MR imaging.

    Non-contrast CT scan may demonstrate increased attenuation in thrombosed veins (cord sign). Contrast enhanced CT may demonstrate,”empty delta sign”, which occurs when the thrombus fails to enhance within the dural sinus and is outlined by enhanced collateral channels in the falx. This sign is seen in only about 25%-30% of cases but is highly diagnostic for sagittal sinus thrombosis. False positive causes of delta sign include subdural hematoma, and arachnoid granulations. If sagittal sinus thrombosis is suspected, one should look for outward bowing of the superior sagittal sinus wall, which is an abnormal finding [1].
    MR imaging has several advantages over CT in detection of sinus thrombosis. The flow voids routinely seen in the large veins and sinuses make visualization of venous thrombosis easier. The hyper acute thrombus has low signal intensity on both T1-and T2-weighted MR images. The effect is more pronounced on T2-weighted MR images. At about 3 weeks period, the clot may have low signal on all sequences and may recanalize with or without thrombus signal. MR venography may show loss of vascular flow signal or a frayed appearance of the venous sinus. Indirect signs of thrombosis include the presence of collateral flow [4].

References:

1. Virapongse C, Cazenave C, Quisling R, Sarwar M, Hunter S. The empty delta sign: frequency and significance in 76 cases of dural sinus thrombosis. Radiology 1987; 162:779-785.
2. Yuh WT, Simonson TM, Wang AM, Koci TM, Tali ET, Fisher DJ, Simon JH, Jinkins JR, Tsai F. Venous sinus occlusive disease: MR findings. AJNR Am J Neurorad 1994; 15:309-316.
3. Ptullu MS, Deshmukh CT, Save SU, Bhoite BK, Bharucha BA. Superior sagittal sinus thrombosis: a rare complication of nephrotic syndrome. J Postgrad Med 1999; 45:120-122.
4. Provenzale JM, Joseph GJ, Barrborial DP. Dural sinus thrombosis: findings on CT and MR imaging and diagnostic pitfalls. AJR Am J Roentgenol 1998; 170:777-783.