Presentation

83M who presented with orbital congestion

Diagnosis

Mild left globe proptosis, with increased size, edema, and enhancement of the ocular muscles and intra-conal soft tissues including the optic nerve sheath. Associated preseptal periorbital soft tissue edema extending to the left zygoma.
Asymmetrically dilated left superior ophthalmic vein with preserved flow void.
Fusiform ectasia and heterogeneous T2 flow-void signal intensity of the bilateral cavernous carotid arteries, compatible with turbulent flow.
TOF sequence images demonstrate arterial flow signal within the left cavernous sinus and superior opthalmic vein
Left sided pachymeningeal enhancement in the anterior and middle cranial fossa

Mild global cerebral volume loss and prominent sulci
Bilateral symmetric prominent perivascular spaces
Left thalamic chronic lacunar infarct
Irregularity of the bilateral V4 segments, especially on the left, likely atherosclerotic. Irregularity of the basilar artery, also likely due to atherosclerosis.

Time-of-flight (TOF) MRA shows arterial flow signal within the left cavernous sinus and an asymmetrically enlarged left superior ophthalmic vein, consistent with a carotid-cavernous fistula (CCF) most likely arising from the left internal carotid artery.
Partially visualized smooth pachymeningeal enhancement overlying the left anterior and middle cranial fossa. Possible etiologies include abnormal flow-related enhancement due to ipsilateral CC fistula or less likely meningeal infection/inflammation.
CCFs can be classified as either direct (usually the result of trauma) or indirect (can be related to Ehlers-Danlos or fibromuscular dysplasia)
TOF angiography is way to image vessels without the use of contrast An excellent review on the physics of TOF can be found here: youtube.com/watch?v=kBrLUaEJaLU.