Variations in the cerebral venous anatomy and pitfalls in the diagnosis of cerebral venous sinus thrombosis: Low field MR experience

Background: Knowledge of variations in the cerebral venous anatomy and apparent signal abnormalities seen on Magnetic resonance (MR) angiography are essential to avoid over-diagnosis of cerebral venous sinus thrombosis (CVST), while interpreting the MR angiograms.
Aims: To evaluate the variations of cerebral venous anatomy and signal abnormalities by using 3D phase contrast MR angiography performed in a 0.5 Tesla MRI scanner.
Materials and Methods: One hundred patients who underwent MR imaging and MR angiography examinations at our institution from March 2004 to February 2005, with normal MR imaging of brain were studied retrospectively. Patients with clinical suspicion of CVST and patients who underwent color doppler evaluation for suspected deep vein thrombosis were excluded.
Results: The superior sagittal, straight sinus and the internal cerebral veins were visualized in all patients. There was hypoplasia of the right transverse sinus in 13 patients, left transverse sinus in 35 patients, right sigmoid sinus in 6 patients and left sigmoid sinus in 19 patients. Absence of transverse sinus on left side was observed in one patient and absence of sigmoid sinus in 2 patients on left side. Flow gaps were observed in non-dominant transverse sinus, sigmoid sinus as well as transverse sigmoid sinus junctions. The occipital sinus was visualized in 17 patients.
Conclusions: MR angiography done at low field strengths is also a reliable method, for assessing cerebral venous sinuses. Awareness of the normal anatomical variations of venous sinuses and apparent MR angiographic flow gaps prevent misdiagnosis of cerebral venous sinus thrombosis.

Keywords
MR angiography, cerebral venous anatomy, cerebral venous sinus thrombosis, cerebral venous thrombosis, Low field MR.