Headache, Altered Mental Status

John R. Gaughen, Jr., M.D.

April 22, 2005

Discussion

Venous sinus thrombosis is a relatively elusive diagnosis. Clinical presentation is extremely variable, ranging from nonspecific findings, such as headache, nausea, or vomiting, to focal neurologic findings such as seizures. It can also present as psychiatric symptoms. When complicated by infarction, stroke symptoms are observed. Because of its amorphous presentation, a high level of suspicion is often needed for prompt diagnosis. Multiple predisposing factors exist, including (but not limited to) hypercoagulable state, extrinsic compression or invasion, dehydration, and pregnancy. It should be noted, however, that 25% of patents with venous sinus thrombosis have no identifiable predisposition. CT and MRI (including CTA and MRA/MRV) are the imaging modalities of choice for diagnosis. On unenhanced CT, the thrombosis will appear hyperattenuating (the "delta" sign), while on enhanced scans, a filling defect can be identified within the thrombosed sinus (the "reverse delta" sign). Associated infarcts are variable, and as many as 50% have associated hemorrhage. Venous sinus thrombosis should be an etiologic consideration in bilateral infarcts, infarcts not conforming to an arterial territory, or hemorrhagic infarcts. MRI detects hemorrhagic infarcts with exquisite sensitivity, showing restricted diffusion on diffusion-weighted images and blooming of hemorrhage on gradient-echo images. Findings in uncomplicated thrombosis are less obvious, manifesting as absence of the normal sinus flow voids on spin-echo T1-weighted images. The signal intensity of the clot will vary depending on its age. MRV is the best noninvasive test for diagnosis of venous sinus thrombosis, using either time-of flight or phase contrast techniques.

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