Pejman Jabehdar Maralani
Abnormal signal intensity in dural venous sinuses on routine brain MRIs that do not contain dedicated MR venogram (MRV) sequences is a common occurrence in daily practice. Loss of flow void on T2 or high signal on FLAIR in dural venous sinuses can be due to slow flow or the presence of dural venous sinus thrombosis (DVST). Slow flow is usually due to stenosis or hyperplastic sinuses, which do not pose any immediate health risks, though sinus stenosis may be implicated in idiopathic intracranial hypertension. However, DVST can have significant consequences in terms of venous infarct and hemorrhage. We decided to design a study to see if any or a combination of imaging findings can favor slow flow over DVST or vice versa.
In an ideal world, we would have added MRV sequences to a large group of cases undergoing routine brain MRI, which would have been a very costly project. Therefore, we decided to design this as a retrospective study. We retrieved all MR venograms at our institution and separated the MRV sequences from the rest of the data. We also retrieved all CT venograms (CTVs) that were done within 48 hours of a routine MRI. We made sure these cases had not received anticoagulation between MRI and CTV. We came up with 3 datasets: MRV-only sequences, CTVs, and MRI without MRV sequences.
We looked at classic signs of DVST, including high signal on sagittal T1, loss of flow void on axial T2, loss of flow void or hyperintense signal on FLAIR, increased susceptibility effects on axial GRE and SWI, high signal on axial DWI, and the presence of filling defects on axial contrast-enhanced SE-T1WI and/or on contrast-enhanced 3D-T1WI. In each case, an evaluation of all sequences of interest was performed at the same time to reflect usual clinical practice.