From the Guidelines
Isolated cortical venous thrombosis on MRI FLAIR sequences typically appears as a hyperintense signal within the affected cortical vein, representing the thrombosed blood. This hyperintensity follows the course of the vein and may be accompanied by surrounding vasogenic edema in the adjacent brain parenchyma, also appearing hyperintense on FLAIR 1. The affected cortical vein may appear enlarged compared to normal veins. Additional findings may include localized gyral swelling and subtle hemorrhagic changes, though these might be better appreciated on other sequences like susceptibility-weighted imaging (SWI) or gradient echo sequences.
In the subacute phase, the thrombus may demonstrate mixed signal intensity. The hyperintense signal in the vein represents methemoglobin in the thrombus, while the surrounding edema results from venous congestion and local ischemia due to impaired venous drainage 1. These FLAIR findings are important to recognize because isolated cortical venous thrombosis can be subtle and easily missed without careful attention to the cortical veins and their signal characteristics.
Key characteristics of isolated cortical venous thrombosis on MRI FLAIR include:
- Hyperintense signal within the affected cortical vein
- Surrounding vasogenic edema in the adjacent brain parenchyma
- Enlarged cortical vein compared to normal veins
- Localized gyral swelling and subtle hemorrhagic changes
- Mixed signal intensity in the subacute phase due to methemoglobin in the thrombus.
It is crucial to consider these findings in the context of the patient's clinical presentation and other imaging sequences to establish an accurate diagnosis and guide appropriate management, as outlined in the guidelines for the diagnosis and management of cerebral venous thrombosis 1.
From the Research
Isolated Cortical Venous Thrombosis MRI FLAIR Findings
- MRI FLAIR findings in isolated cortical venous thrombosis (ICVT) include hypointense signal intensity on FLAIR images, as reported in 6 out of 8 patients in a study 2.
- Parenchymal hyperintensities on FLAIR images were observed in close vicinity to the thrombosis in 6 out of 8 patients, indicating vasogenic edema or other parenchymal changes 2.
- FLAIR images may show signal-intensity changes, which can decrease both in volume and intensity during follow-up, as observed in a study of 8 patients with ICVT 2.
- T2-weighted MRI, including FLAIR sequences, was found to be a useful diagnostic tool in patients with ICVT, particularly in those with new-onset seizures 3.
Diagnostic Value of MRI FLAIR in ICVT
- MRI, including FLAIR sequences, is one of the most frequently used diagnostic modalities for ICVT, with 73% of cases diagnosed using MRI 4.
- The diagnostic value of MRI FLAIR in ICVT is high, particularly when combined with other MRI sequences such as T2*GE imaging, which can detect magnetic susceptibility effects (MSE) at the site of the thrombosis 2.
- Susceptibility-weighted imaging, which includes T2*GE imaging, was found to be the most sensitive imaging technique in diagnosing ICVT in a case series of 7 patients 5.