Magnetic Resonance Imaging Evidence of an Occipital- Straight Sinus Dural Arteriovenous Fistula Causing Severe Bilateral Thalamic Oedema: A Case Report

An 81-year-old woman, with a 3-month history of tinnitus and vertigo, presented with a deterioration of symptoms. Magnetic resonance imaging (MRI) of the brain, using fluid attenuated inversion recovery (FLAIR) and T2 weighted (T2WI) images, demonstrated hyperintensity and swelling of the bilateral thalami, medial parietal lobes, occipital lobes, and left cerebellar hemisphere. She was referred to us with the suggestion of a brain tumour that had spread into the bilateral thalami, or encephalitis. A review of the MR images, however, demonstrated dilatation of a vein on the surface of the cerebellar hemisphere on the T2WI image. Susceptibility weighted imaging (SWI) revealed small and multiple hypointense lesions, indicating microhaemorrhages, in the bilateral thalami and left cerebellar hemisphere. The time of flight source imaging demonstrated small hyperintense dots in the wall of the occipital and straight sinus. Finally, a digital subtraction angiogram (DSA) revealed a dural arteriovenous fistula (DAVF) in the occipito-straight sinus with reflux flow into the straight sinus (Borden Type II). A transvenous embolization and trans-arterial embolization were performed, in an emergency setting, for the occipital sinus and dural shunt, respectively, with the aim of preserving the antegrade flow of the straight sinus. The DSA following the endovascular treatment showed the disappearance of shunt flow and recovery of the antegrade flow in the straight sinus. Therefore, this case report highlights that meticulous analysis of MRI scans help diagnose DAVF, which results in quick and radical treatment.