Transvenous Embolization for a Diploic Arteriovenous Fistula Presenting With Tinnitus: A Case Report.

Intraosseous arteriovenous fistula (AVF) is rare, and diploic AVF is an even rarer subtype with very few reported cases. We describe a 30-year-old man who presented with bilateral pulsatile tinnitus. Magnetic resonance imaging (MRI) revealed abnormal signals in the occipital region, prompting digital subtraction angiography (DSA), which demonstrated arteriovenous shunting from transosseous branches of both occipital arteries (OAs) converging at a single point within the diploë. The shunted flow drained into the transverse sinus via a diploic vein. Although venous drainage was antegrade without cortical reflux, the patient experienced intolerable tinnitus. Transvenous embolization (TVE) was performed targeting the outflow vein immediately distal to the shunt point, where all shunted flow converged. This resulted in rapid resolution of tinnitus without neurological deficits. This case highlights an exceedingly rare instance of occipital diploic AVF in the posterior fossa and emphasizes that early recognition and definitive endovascular embolization can achieve a curative outcome before complications develop.