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Title: Imaging of indirect carotid cavernous fistula comparing advanced mri sequences with digital subtraction angiography
Authors: Sathish K
Issue Date: Dec-2019
Publisher: SCTIMST
Abstract: Carotid-cavernous fistulas (CCFs) are abnormal arteriovenous communications either directly between the internal carotid artery (ICA) and the cavernous sinus or between the dural branches of the internal and external carotid arteries. Several classification schemes have categorized CCFs according to aetiology (traumatic or spontaneous), hemodynamic features (high versus low flow), or the angiographic arterial architecture (direct or indirect). Direct CCFs usually arise after trauma or a ruptured aneurysm. These fistulae are less likely to resolve spontaneously and may require intervention if symptomatic. The remaining types are indirect and are best described as dural arteriovenous malformations. Their rate of flow and exact aetiology are variable. They have been associated with pregnancy, cavernous sinus thrombosis, sinusitis, and minor trauma. Most of the patients are managed conservatively and may require intervention if there is any deterioration during follow up. (1) Intra-arterial digital subtraction angiography (DSA) is the standard of reference for the diagnosis of CSDAVFs. Its high spatial and temporal resolution facilitates the accurate analysis of feeders, venous drainage, and fistula sites. However, DSA is invasive and not without possible complications; morbidity of 0.03% and mortality of 0.06% have been reported for patients undergoing diagnostic cerebral angiography(2,3). Therefore, a noninvasive, reliable method is needed for the appropriate selection of patients with CSDAVF with high risk (aggressive symptoms), exclusion of patients with CSDAVF considered benign and for follow-up. Carotid cavernous fistula descriptions are with type, location, laterality, size of fistula, feeding arteries, draining veins and cortical venous reflux. 7 Recently few studies are published on cranial dural arteriovenous fistulas (cDAVF) comparing the efficacy of advanced vascular MR imaging with DSA. Comparison of 3D-TOF (3T) with DSA in the evaluation of intracranial DAVF showed good intermodality agreement in the gross characterization of DAVF(4). Few studies showed SWI can reliably detect the fistulous point, presence of cortical venous reflux in cases of DAVF and also helps in differentiating nidus from haemorrhage and calcification in cases of brain AVM(5,6). Susceptibility-weighted angiography (SWAN) is a new 3D T2*- based gradient-echo sequence generating several echoes that are read out at different TE times, allowing high resolution visualization of both cerebral veins and arteries. SWAN sequence has a potential role for the diagnosis of intracranial DAVF in visualising intracranial arteriovenous shunt(7). Silence Magnetic resonance angiography is a relatively new technique available in 3.0 Tesla Magnetic Resonance scanners. The advantages of this arterial spin labelling (ASL) based ultra-short echo-time technique is that it is less affected by susceptibility effects and has excellent background suppression. Few preliminary studies have found that the vascular anatomy is better depicted on Silence magnetic resonance(8). To our knowledge, there are no systematic studies on the reliability of unenhanced 3T 3D TOF MRA, Silent MRA and SWAN for assessing feeders, fistula sites, and venous drainage of CSDAVFs. Thus, this intended to study the utility of these noninvasive magnetic resonance angiography techniques to determine the angiomorphology of CCF, in treatment planning and follow up. If found reliable it may supplant DSA in follow up imaging.
Appears in Collections:Imaging Sciences and Intervention Radiology

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