Venous sinus thrombosis and associated hemorrhagic infarction.
CT - Ill-defined area of low-attenuation in the right
temporo-occipital region with irregular high attenuation,
consistent with hemorrhagic infarction. CTA - Severe paucity of
blood flow in the right temporo-occipital region. Lack of filling
in the right sigmoid and transverse sinuses. Note the patency of
the superior sagittal and left transverse sinuses. MRI - TSE T2WI
demonstrates high signal intensity in the right temporo-occipital
region, as well as soft tissue in the sagittal sinus, indicative of
thrombus. DWI demonstrates corresponding restricted diffusion. GRE
T2WI (not shown) would demonstrate blooming, consistent with
hemorrhage. MRV - Evidence of disease progression from the CTA,
with lack of filling in the posterior superior sagittal and
bilateral transverse sinuses.
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.
1. Grossman, Robert I. Yousem, David M. The Requisites:
Neuroradiology. Mosby, Philadelphia, 2003. 2. Patel, Maresh R.
Brain, Venous Sinus Thrombosis. eMedicine.