Dural arteriovenous fistulas (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 findings, 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 fistulous pouch involving the anterior condylar confluence 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 efficacy (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.
Keywords: 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 resonance 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; anterior condylar confluence; anterior condylar vein; dural arteriovenous fistula; endovascular therapy; hypoglossal canal; skull base vein; transvenous embolization; vascular disorders.