Cerebral Venous Thrombosis (CVT)

Diagnosis Definition

• In order of frequency, cerebral venous thrombosis (CVT) involves the dural sinuses, deep venous system, and cortical veins; multiple locations are found in up to 90% of patients
• CVT results from local processes that alter venous flow (sinus trauma, regional infection such as mastoiditis, and neoplastic invasion/compression) or systemic causes (protein S/C deficiencies, peripartum state, oral contraceptive use, and hypercoagulable states secondary to malignancy); in 25% of cases the cause is unknown
• Generalized neurologic symptoms (most commonly headache) and focal neurologic deficits, including seizure, may result; clinical manifestations can fluctuate with concurrent thrombosis and recanalization

Imaging Findings

• CT venography (CTV) and MRV are the gold standards for the diagnosis of CVT
• Classically, CVT on noncontrast CT (NCCT) is a hyperattenuating thrombus in the occluded vessel; on MRI it is the absence of a flow void
• The signal intensity of CVT on MRI varies according to the paramagnetic effects of hemoglobin: (0–5 days) isointense on T1, hypointense on T2 (can mimic normal flow void); (6–15 days) hyperintense on T1 and T2 (most different from normal flow states and almost always abnormal); (>15 days) iso- or hyperintense on T2, isointense on T1
• The “empty delta sign” refers to a central filling defect on contrast CT or MRI and is typically seen in the superior sagittal sinus (SSS) or torcula
• The “cord sign” refers to a hyperdense cortical vessel on NCCT that is seen with cortical vein thrombosis
• “Flame-shaped” hemorrhage in the parasagittal frontal/parietal lobes is a typical finding in SSS thrombosis

KEY IMAGES

Pearls

• CVT mimics include venous anatomic variants (sinus atresia or hypoplasia), asymmetric/variant sinus drainage (occipital sinuses, sinus duplication), slow turbulent flow, and normal sinus filling defects (arachnoid granulations, intrasinus septa)
• Increased attenuation in the venous sinuses may also be seen with dehydration and elevated hematocrit

References

1. Leach JL, Fortuna RB, Jones BV, Gaskill-Shipley MF.  Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of Findings, and Diagnostic Pitfalls.  RadioGraphics 2006; 26:S19 –S43
2. Yuh WT, Simonson TM, Wang AM, et al. Venous sinus occlusive disease: MR findings. AJNR Am J Neuroradiol 1994; 15:309 –316