Normal Variations and Artifacts in MR Venography that may cause Pitfalls in the Diagnosis of Cerebral Venous Sinus Thrombosis.

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1 Normal Variations and Artifacts in MR Venography that may cause Pitfalls in the Diagnosis of Cerebral Venous Sinus Thrombosis. Poster No.: R-0005 Congress: 2015 ASM Type: Scientific Exhibit Authors: A. Pallewatte, N. Liyanage ; Colombo/LK, Melbourne/AU Keywords: Normal variants, Diagnostic procedure, MR-Angiography, Vascular, Neuroradiology brain, Artifacts DOI: /ranzcr2015/R Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply RANZCR's endorsement, sponsorship or recommendation of the third party, information, product or service. RANZCR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold RANZCR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies,.ppt slideshows,.doc documents and any other multimedia files are not available in the pdf version of presentations. Page 1 of 8

2 Purpose MR venography is a widely used non invasive imaging technique to diagnose Cerebral Dural Venous Sinus thrombosis (CVST) and intracranial venous abnormalities [1]. Time of Flight(TOF) is the most commonly used non contrast MRV technique[2]. The diagnosis of CVST on MRV primarily depends on non-visualization of a venous sinus or a segment appearing like filling defects. However there are many normal variations and technical artifacts occuring on MRV simulating filling defects which can mimic CVST causing diagnostic pitfalls. These include absent, hypoplasic or asymmetric venous sinuses and anomalous veins [3].Furthermore reconstruction artifacts can appear as flow gaps of different lengths[4,5].this study aims to study the frequencies, locations and imaging characteristics of these variations and artifacts on MR venography. Methods and materials We retrospectively reviewed 218 normal Cerebral MR venograms of adult patients who underwent MR Venography as a part of routine headache protocol (GE Signa XT 1.5T). Ethical approval was obtained from the Institution. Brain MRI scans of these patients were reported as normal by the staff neuro-radiologists. Furthermore CVST had been clinically and radiologically excluded in all. We studied radiological appearances of major dural sinuses, the visualized venous anatomy and extent of flow gaps (as percentage) using images available on PACS. Their individual Incidences were recorded. Transverse sinus flow gaps were analysed and documented on the site and percentage length compared to the total length of the ipsilateral transverse sinus. Anomalous patterns of venous drainage such as occipital sinus were recorded. Patients' demographic data and clinical information were also obtained from the hospital data base. Results The superior sagittal sinus(sss), the vein of Galen, the Internal Cerebral Vein and the straight sinus were observed constantly in almost all patients. Arachnoid granulations causing characteristic short flow gaps were seen in SSS in 4.6%(10/218) cases and in the straight sinus in 5.5(12/218) cases. These were common close to the Torcula Herophili and therefore could be misinterpreted as CVST. In the Transverse sinus, right dominance, left dominance and co-dominance were noted in 58%, 15% and 27% Page 2 of 8

3 respectively. Transverse sinus was hypoplastic in 25% and aplastic in 11% with the majority of them occurring on the left side. Flow gaps in the transverse sinuses were noted in 35/218 with 77% (27/35) on non dominant transverse sinus, 14% (5/35) in the dominant and only 9% (3/35 ) in co-dominant transverse sinus. Flow gaps were also found in Superior Sagittal Sinus (SSS) in 8.5%(18/218) and in straight sinuses in 3.1%(8/218). The Occipital Sinus was present in 6.6% (14/218) and was associated with a hypoplasic or aplastic transverse sinus providing alternative drainage pathways from the straight sinus to the Internal Jugular Vein. Table 1: Variations of the Superior Sagittal Sinus (SSS) References: The National Hospital of Sri Lanka - Colombo/LK Images for this section: Fig. 1: Dominance of Transverse Sinuses 1a Left dominant transverse sinus (15%) 1b Right dominant transverse sinus (58%) 1c Codominant transverse sinuses (27%) ( The frequency of variants as seen on our study of 218 cases is given within brackets) Page 3 of 8

4 Fig. 2: Occiptal Sinus (6.6%) ( with absence of right transverse sinuses) Fig. 3: Transverse Sinus Flow Gaps 3a.Flow gap of 50% in left transverse sinus 3b. Flow gap<25% in right transverse sinus Page 4 of 8

5 Fig. 4: Arachnoid granulations- Commonest locations and appearences Fig. 5: Superior Sagittal Sinus 5a Hypoplasia of anterior 25% of Superior Sagittal Sinus(3.3%) 5b Hypoplasia of anterior 50% of Superior Sagittal Sinus (2.4%) Page 5 of 8

6 Fig. 6: Normal Anatomy of the cerebral venous system Page 6 of 8

7 Conclusion As shown above, these variants and artifacts on MRV occur often, follow a constant imaging pattern. Furthermore their locations sometimes coincide with sites where CVST is also common and may cause diagnostic difficullties. Transverse sinus flow gaps are a common occurrence in MRV and found more frequently on the non-dominant transverse sinus. Combination of a small sinus size, a slow or complex flow pattern, an image acquisition plane not parallel to the sinus could be the likely causes for these findings[2,6]. Therefore these variants and artifacts can be potential pitfalls in the MRV diagnosis of CVST specially where there are no supportive imaging features such as brain infarcts [6,7]. It is important for the interpreting radiologist to be aware of relevant MRI characteristics to avoid misinterpretation of these variants and artefacts as CVST. It is also essential to assess the relevant source images carefully along with the MRV in order to accurately evaluate venous structures and reduce potential diagnostic errors[8]. Personal information References 1.Ayanzen RH, Bird CR, Keller PJ, McCully FJ, Theobald MR, Heiserman JE. Cerebral MR venography: Normal anatomy and potential diagnostic pitfalls. Am J Neuroradiol. 2000;21: Leach JL, Fortuna RB, Jones B V., Gaskill-Shipley MF. Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of Findings, and Diagnostic Pitfalls. Radiographics. 2006; S Tubbs, R.S. et al., The oblique occipital sinus: A review of anatomy and imaging characteristics. Surgical and Radiologic Anatomy.2011; 33: Pui MH. Cerebral MR venography. Clin Imaging. 2004;28: Essig, M. et al. High-resolution MR venography of cerebral arteriovenous malformations. Magnetic Resonance Imaging.1999;17: Fofi, L. et al. Cerebral transverse sinus morphology as detected by MR venography in patients with chronic migraine. Headache.2012; 52: Klingebiel R, Bauknecht HC, Bohner G, Kirsch R, Berger J, Masuhr F. Comparative evaluation of 2D time-of-flight and 3D elliptic centric contrast-enhanced MR Page 7 of 8

8 venography in patients with presumptive cerebral venous and sinus thrombosis. Eur J Neurol [Internet]. Wiley-Blackwell; 2007;14(2): : j x 8.Surendrababu N, Subathira, Livingstone R S. Variations in the cerebral venous anatomy and pitfalls in the diagnosis of cerebral venous sinus thrombosis: Low field MR experience. Indian J Med Sci 2006;60: Page 8 of 8