Transverse dural sinuses: incidence of anatomical variants and flow artefacts with 2D time-of-flight MR venography at 1 Tesla.

PURPOSE

This study sought to identify imaging criteria useful in discriminating anatomical variants from thrombosis of the posterior intracranial venous system.

MATERIALS AND METHODS

A total of 102 patients underwent coronal unenhanced two-dimensional time-of-flight (2D ToF) magnetic resonance (MR) venography. Transverse sinus (TS) calibre and asymmetry were considered. Oval (O-FG) and linear (L-FG) flow gaps were recorded. Several slices of the 2D ToF sequence were applied perpendicularly to the TS within each FG to avoid in-plane saturation.

RESULTS

Mean calibre of the right TS was significantly greater than the contralateral sinus (6.5 mm+/-1.84 vs 5.1 mm+/-1.72). Right and left dominance was observed in 61% and 17% of cases, respectively. The mean right-left TS diameter was 5.77 mm. Among 204 TS, 44 L-FG and 42 O-FG were observed. Partial L-FG (<2/3 of TS) never involved the distal TS. No L-FG was observed in a dominant TS. Supplementary sagittal 2D ToF images disclosed blood flow in all but two L-FGs. O-FGs were mostly observed laterally (91%).

CONCLUSIONS

L-FGs in a dominant TS, partial L-FGs in the distal part or O-FG in the medial part of any TS, a left-right mean diameter <3 mm and absence of flow even in ToF images perpendicular to the direction of blood flow should raise the suspicion of sinus pathology.