A dural arteriovenous fistula corresponding to the abnormality identified on MRI is noted within the posterior fossa to the right of midline. It receives multiple arterial branches from the right external carotid artery with the largest contribution seemingly from the enlarged ascending pharyngeal artery. Further branches from the internal maxillary artery are also noted.
Moderate contribution from meningohypophyseal arteries from the left ICA are also noted. There is a minor contribution from meningohypophyseal branches of the right internal carotid artery.
There is a small fistulous clump draining into a plexus of veins including a 12 mm venous varicosity. Drainage to multiple cortical veins is evident extending to the sigmoid sinus but also the deep system extending to the straight sinus.
Minimal contribution from the posterior circulation and none from left external carotid artery.