A case of falx cerebelli dural arteriovenous fistula with perimedullary venous reflux after occipital bone fracture.

Intracranial dural arteriovenous fistulas (dAVFs) with perimedullary venous reflux are uncommon but can lead to progressive myelopathy. Although most dAVFs are idiopathic or associated with dural sinus thrombosis, a falx cerebelli dAVF developing after an occipital bone fracture is exceedingly rare and clinically important. We report a 77-year-old patient who presented with 1 month of progressive bilateral lower-extremity weakness, urinary retention, and hiccups, 1 year after an occipital bone fracture. Magnetic resonance imaging showed longitudinal T2-weighted imaging hyperintensity from the medulla to the C4 level with ventral perimedullary flow voids. Cerebral angiography demonstrated a falx cerebelli dAVF fed by bilateral occipital arteries traversing the fracture line with retrograde reflux to intracranial and spinal veins (Borden type III, Cognard type V). Transarterial embolization with n-butyl-2-cyanoacrylate achieved complete angiographic obliteration, and the magnetic resonance imaging abnormalities resolved by 9 months. Falx cerebelli dAVFs after skull fracture are extremely rare but should be considered in patients with progressive myelopathy.