PMC4386113_01
Case 1. a MRA, before angiogram. Note abnormal signal (red arrow) within the posterior aspect of the right cavernous sinus behind the internal carotid artery (white arrow). b Axial T2 MRI after spontaneous thrombosis of the fistula. Note new-onset proptosis OD. c Right internal carotid angiogram, anterioposterior view, initial workup. Clival dAVF (blue arrow) posterior to cavernous sinus and venous drainage down the inferior petrosal sinus (red arrow). d Right internal carotid angiogram, anterioposterior view, after symptoms resolved. No further filling of fistula or petrosal sinus.
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F1
Brain MRA/MRV showed a small focus of high signal intensity within the posterior aspect of the right cavernous sinus suspected of being a venous structure (fig. 1a). Catheter angiography revealed early opacification of a venous network near the clivus just posterior to the cavernous sinus, consistent with a low-flow clival dAVF supplied bilaterally by branches from both the internal and external carotid arteries (fig. 1c). These findings were highly suggestive of thrombosis of the CCF secondary to angiogram contrast dye, but the MRI on that day showed no definite evidence of thrombosis of the cavernous sinus and no dilatation of the superior or inferior orbital veins (fig. 1b). A repeat catheter angiogram revealed a dramatic decrease in shunting of contrast through the vasculature to the clivus, confirming thrombosis of the clival dAVF (fig. 1d).
PMC4386113_02
Case 2. Medusa's head conjunctival venule arterialization. a, b Before embolization. Note the radial spoke-like appearance of the venules as they course away from the limbus, unique to this disease entity. c, d After embolization.
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F2
Slit lamp examination showed dilated, arterialized conjunctival vessels, OS greater than OD (fig. 2a, b). Following embolization, her conjunctival erythema and engorgement improved (fig. 2c, d), but 1 week later, she developed a complete right sixth nerve palsy that resolved over the next several months.
Case 2. a Axial FLAIR MRI, before embolization. Note edema of the right cerebellar tonsil and dentate nucleus (red arrow). b Axial T1 MRI with contrast, 2 weeks after embolization. Note decreased cerebellar enhancement. c Left internal carotid angiogram, anterioposterior view, initial workup. Early filling of vein draining into right cerebellum (arrow). d Left internal carotid angiogram, anterioposterior view, after embolization of the fistula. No further filling of the draining vein. Cast of embolic material in vein (arrow) is subtracted out.
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F3
These findings were suspicious for a dAVF on top of her existing Graves' orbitopathy, and a brain MRI/MRV was performed, which showed a new area of signal abnormality with mild mass effect involving both the right cerebellar tonsil and dentate nucleus, consistent with a subacute ischemic infarct and edema from associated venous congestion (fig. 3a). The patient was urgently referred to neurosurgery for catheter angiography, which revealed a dAVF near the clivus supplied by small branches of the right internal and external carotids as well as the left internal carotid (fig. 3c). The fistula appeared to be completely obliterated on postembolization angiography (fig. 3d). Follow-up brain MRI and MRA 2 months after embolization demonstrated resolving edema in the right cerebellum (fig. 3c).