J Neurosurg Volume 122 • April 2015 literature review J Neurosurg 122:883–903, 2015 D ural arteriovenous fstulas (DAVFs) are abnor- mal communications between dural arteries and dural venous sinuses, meningeal veins, or cortical veins. 20 They account for 10%–15% of intracranial arte- riovenous malformations and are classifed according to the location of the involved sinus, that is, transverse, sig- moid, or cavernous sinus DAVFs. 20 These fstulas can also occur at the skull base, in which case a dural venous sinus may not be directly involved. Grading DAVFs is based on the direction of venous fow within the dural venous sinus (anterograde vs retrograde) and the presence of cortical venous refux. 7,14 Dural arteriovenous fstulas of the hypoglossal canal: systematic review on imaging anatomy, clinical fndings, and endovascular management Björn Spittau, MD, 1 Diego San Millán, MD, 2 Saad El-Sherif, MD, 3 Claudia Hader, MD, 3,4 tejinder Pal Singh, MD, 5 edith Motschall, 6 werner vach, PhD, 6 Horst urbach, MD, 3 and Stephan Meckel, MD 3 1 Institute for Anatomy and Cell Biology, Department of Molecular Embryology, Albert-Ludwigs-University Freiburg; 3 Department of Neuroradiology, University Hospital Freiburg; 6 Center for Medical Biometry and Medical Informatics, Medical Center–University of Freiburg, Germany; 2 Neuroradiology Unit, Department of Diagnostic and Interventional Radiology, Centre Hospitalier du Centre du Valais, Hôpital de Sion; 4 Neuroradiology Unit, Institute of Radiology, Kantonsspital St. Gallen, Switzerland; and 5 Neurological Intervention and Imaging Service of Western Australia, Sir Charles Gairdner & Royal Perth Hospitals, Nedlands, Western Australia, Australia Dural arteriovenous fstulas (DAVFs) of the hypoglossal canal (HCDAVFs) are rare and display a complex angiographic anatomy. Hitherto, they have been referred to as various entities (for example, “marginal sinus DAVFs”) solely described in case reports or small series. In this in-depth review of HCDAVF, the authors describe clinical and imaging fndings, as well as treatment strategies and subsequent outcomes, based on a systematic literature review supplemented by their own cases (120 cases total). Further, the involved craniocervical venous anatomy with variable venous anastomoses is summarized. Hypoglossal canal DAVFs consist of a fstulous pouch involving the anterior condylar confuence and/ or anterior condylar vein with a variable intraosseous component. Three major types of venous drainage are associated with distinct clinical patterns: Type 1, with anterograde drainage (62.5%), mostly presents with pulsatile tinnitus; Type 2, with retrograde drainage to the cavernous sinus and/or orbital veins (23.3%), is associated with ocular symptoms and may mimic cavernous sinus DAVF; and Type 3, with cortical and/or perimedullary drainage (14.2%), presents with either hemorrhage or cervical myelopathy. For Types 1 and 2 HCDAVF, transvenous embolization demonstrates high safety and ef fcacy (2.9% morbidity, 92.7% total occlusion). Understanding the complex venous anatomy is crucial for planning alternative approaches if standard transjugular access is impossible. Transarterial embolization or surgical disconnection (morbidity 13.3%–16.7%) should be reserved for Type 3 HCDAVFs or lesions with poor venous access. A conservative strategy could be appropriate in Type 1 HCDAVF for which spontaneous regression (5.8%) may be observed. http://thejns.org/doi/abs/10.3171/2014.10.JNS14377 Key worDS dural arteriovenous fistula; hypoglossal canal; anterior condylar confluence; anterior condylar vein; skull base vein; endovascular therapy; transvenous embolization; vascular disorders aBBreviatioNS ACC = anterior condylar confluence; ACV = anterior condylar vein; AIVVP = anterior internal vertebral venous plexus; CTA = CT angiography; DAVF = dural arteriovenous fistula; DSA= digital subtraction angiography; EVT = endovascular treatment; HCDAVF = hypoglossal canal DAVF; ICAVP = internal carotid artery venous plexus (of Rektorzik); IJV = internal jugular vein; IPS = inferior petrosal sinus; LCV = lateral condylar vein; MEV = mastoid emissary vein; MRA = magnetic reso- nance angiography; NBCA = N-butyl cyanoacrylate; PCV = posterior condylar vein; PT = pulse-synchronous tinnitus; PVA = polyvinyl alcohol; SOV = superior ophthalmic vein; TAE = transarterial embolization; TOF = time-of-flight; TVE = transvenous embolization; VA= vertebral artery; VAVP = vertebral artery venous plexus; VVP = vertebral venous plexus. SuBMitteD February 18, 2014. aCCePteD October 7, 2014. iNCluDe wHeN CitiNg Published online November 21, 2014; DOI: 10.3171/2014.10.JNS14377. DiSCloSure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. 883 ©AANS, 2015