Purpose: The purpose of the study was to know the normal anatomy and its variants and identify the imaging criteria that discriminate normal anatomical variants from thrombosis and other pathological condition. To check the accuracy of non enhanced 3D phase contrast magnetic resonance venography (3D PC-MRV) vs contrast enhanced magnetic resonance venography (CE-MRV).

Material and Methods: It is a descriptive type of observational study done on 192 patients who were referred for investigation of part other than brain and who had normal results of MR imaging of the brain (having no manifestations of cerebrovascular diseases) were recruited into the study. The larger cerebral veins and all sinuses, including the occipital sinuses, were assessed by using oblique sagittal non enhanced 3D PC-MR venography. Among 192 cases, The 81 cases also had CE-MRV provided study material for comparisons with non contrast MR venography.

Results: Hypoplastic left TS was most common anatomical variation in 31.8% (61). Hypoplastic right TS 6.25% (12), aplastic right TS one (0.52%), aplastic left TS aplastic/atretic in 3.1% (6) cases, hypoplastic right SS 6 (3.1%) and hypoplastic left SS in 25 % (49) in cases. OFG/AG was seen in 21% (42) cases. Most common variation of SSS was hypoplasia of anterior one third in 18.8% (36) and bifurcated near lambdoid suture of the cranium in 11% (21). The deep venous system is invariably consistent, except small variations in BVOR. In 76 (41.5%) of 192 cases without occipital sinuses, absent or hypoplastic TS were found. Nine patients had occipital sinuses. In seven (78%) of nine patients with occipital sinuses, absent or hypoplastic transverse sinuses were shown.

Conclusion: These anatomical variants and artifacts can be a potential pitfall in the MRV diagnosis of CVST, especially when there are no supportive imaging features such as brain infarcts or appropriate clinical background. Therefore, it is essential for radiologist to be familiar with MRV characteristics and anatomy so that they are not misinterpreted as CSVT.  3D PC MRV is a great option for patients with gadolinium allergy/renal insufficiency/pregnant patients can provide comparable results to CE MRV.

Keywords: 3D phase contrast magnetic resonance venography, contrast enhanced magnetic resonance venography, superior sagittal sinus, transverse sinus, sigmoid sinus and arachnoid granulations.

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Dr Kirti Chaturvedy

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