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Show Issues in the Diagnosis and Management of the Papilledema Shunt Neeraj Chaudhary, MD, Julius Griauzde, MD, Joseph J. Gemmete, MD, Aditya S. Pandey, MD, Jonathan D. Trobe, MD Background: Dural arteriovenous fistulas (DAVFs) that shunt blood into the transverse or superior sagittal venous sinuses cause papilledema by raising intracranial pressure ("the papilledema shunt"). Such fistulas pose unique diag-nostic and therapeutic challenges. Methods: Case report and literature review. Results: In a patient presenting with papilledema, non-invasive brain vascular imaging disclosed subtle signs of a DAVF. Digital angiography delineated the DAVF and revealed cortical venous reflux. After three transarterial emboliza-tions with ethylene vinyl alcohol, the DAVF was closed and papilledema resolved. Conclusions: The imaging features of a DAVF that cause papilledema may be subtle on non-invasive vascular imaging. If overlooked, and lumbar puncture is performed, there is a substantial risk of brain herniation. Cortical venous reflux, which may be relatively common in these DAVFs, impels the need for endovascular closure. The transvenous route, often employed for closing cavernous sinus DAVFs, should be avoided because of the dangers of dural venous sinus thrombosis. Journal of Neuro-Ophthalmology 2014;34:259-263 doi: 10.1097/WNO.0000000000000118 © 2014 by North American Neuro-Ophthalmology Society Dural arteriovenous fistulas (DAVFs, arteriovenous shunts), comprised typically meningeal arteries abnor-mally communicating with a dural venous sinus or other cerebral veins, constitute about 10%-15% of intracranial vascular malformations (1-6). Three DAVFs have predom-inantly ophthalmic manifestations: 1. The "red eye" shunt, a fistula located in or near the cavernous sinus that drains primarily into the orbit. It can cause reduced visual acuity owing to retinal venous stasis or steal from optic nerve circulation, elevated intra-ocular pressure, periocular pain, ptosis, and ophthalmo-plegia largely due to orbital and ocular venous congestion. 2. The "white eye" shunt, a fistula also located in or near the cavernous sinus but draining posteriorly into the petrosal and pterygoid venous sinuses. Accordingly, the presentation is usually without any features of orbital venous congestion but with reduced visual acuity owing largely to vascular steal from the intracranial optic nerve and ophthalmoplegia owing to vascular steal from vasa nervorum of ocular motor cranial nerves (7). 3. The "papilledema" shunt, a fistula located in the sagittal, transverse, or sigmoid sinus. "Arterialization" of these major draining sinuses raises venous and intracranial pressure (9). The cavernous red eye and white eye shunts are well described. The transverse and superior sagittal sinus shunts have long been recognized (9), but the fact that they can give rise to vision-threatening papilledema has largely escaped notice. An authoritative review of ophthalmic man-ifestations of intracranial vascular abnormalities did not mention them (10). These shunts present unique diagnostic and management challenges. To highlight those challenges, we present a typical case and describe its management. CASE REPORT A 35-year-old woman reported episodic bright spots in the field of vision of her right eye. They lasted less than a minute and were usually precipitated by assuming the upright posture. She had had no other medical problems but acknowledged a 20-lb weight gain over the preceding 6 months. She was taking no medications and had no pertinent family history. The patient had a body mass index of 29 kg/m2, normal vital signs, and the remainder of her physical examination Departments of Radiology (Neurointerventional Radiology) (NC, JG, JJG, ASP), Neurosurgery (NC, JJG, ASP), Ophthalmology (JDT), and Neurology (JDT), University of Michigan Health System, Ann Arbor, Michigan. The authors report no conflicts of interest. Address correspondence to Jonathan D. Trobe, MD, Kellogg Eye Cen-ter, 1000 Wall Street, Ann Arbor, MI 48105; E-mail: jdtrobe@umich.edu Chaudhary et al: J Neuro-Ophthalmol 2014; 34: 259-263 259 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. was unremarkable. Visual acuity was 20/20 in each eye. The pupils constricted normally to light without relative afferent defect. The external ocular examination was normal, includ-ing eye movements and alignment. Biomicroscopic examina-tion was normal, and intraocular pressures were 14 mm Hg in each eye. Automated visual fields showed mean deviations of 22.4 dB in the right eye and 21.7 dB in the left eye without clusters of high threshold points. Ophthalmoscopy disclosed bilateral optic disc edema (Fig. 1). Although a diagnosis of idiopathic intracranial hyper-tension (IIH) was believed likely, brain magnetic resonance imaging (MRI) unexpectedly showed subtle findings of a vascular anomaly centered on the right transverse-sigmoid sinus junction (Fig. 2A), later confirmed on computed tomographic angiography (Fig. 2B). Catheter angiography delineated a DAVF centered on the right transverse-sigmoid sinus junction with multiple arterial feeders from branches of the right external carotid and right vertebral arteries (Fig. 3A). Cortical venous reflux (CVR) was present (Fig. 3B). The patient underwent staged transarterial embolization of the DAVF with ethylene vinyl alcohol (EVOH or Onyx; Covidien, Mansfield, MA) until all CVR was obliterated on 6-month follow-up angiography (Fig. 4). Thirteen months after final embolization, the patient's papilledema had resolved, and she remained free of visual symptoms. There were no procedure-related complications. DISCUSSION In the case presented here, a DAVF shunted blood into the right transverse-sigmoid sinus junction in a patient whose only clinical manifestations of headache and papilledema were attributable to increased intracranial pressure. In a pre-vious report of 2 such DAVFs, abnormally high pressure gradients were recorded manometrically across the dural venous sinuses before embolization and normalized after obliterative embolization and disappearance of papilledema (11). Because high intracranial pressure is not uniformly re-ported in all such DAVFs, these authors and others (9) spec-ulated that the presence of stenosis, thrombosis, or atresia in sinuses distal to the DAVF might be contributory factors. The DAVF that gives rise to papilledema (herein called the papilledema shunt) is actually the most common type of intracranial dural fistula (8). Its pathogenesis remains uncer-tain, although head trauma or surgery, the postpartum state, and previously documented dural venous sinus thrombosis are known triggers. It is somewhat more common in women, and relatively uncommon in children. Adults of any age are at risk (8). Our case highlights the diagnostic and management challenges of the papilledema shunt. The presumptive diagnosis before imaging was IIH. Because clinicians were not expecting a DAVF, they ordered the MRI and magnetic resonance angiography studies, standard in the evaluation of FIG. 1. At presentation, there is bilateral optic disc edema. FIG. 2. A. T2 axial brain magnetic resonance imaging demonstrates subtle serpiginous flow voids (arrows) in the right occipital region. B. Coronal computed tomography angiogram confirms that these are dilated vessels (arrows) suggestive of vascular malformation. 260 Chaudhary et al: J Neuro-Ophthalmol 2014; 34: 259-263 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. suspected IIH. Those studies showed only a subtle vascular abnormality that was fortunately identified by an astute radiologist and confirmed with computed tomographic venography. Had the fistula not been detected, the patient might have undergone lumbar puncture as part of a standard evaluation of suspected IIH, a procedure that this setting carries the risk of life-threatening cerebellar tonsillar herniation (8,12). As our case illustrates, initial imaging of patients with papilledema must rule out not only dural sinus thrombosis, but also DAVF. Noninvasive imaging may detect only subtle signs of the shunt, requiring special attention on the part of the radiologist. There are no clinical features that would aid the examiner in distinguishing increased intra-cranial pressure caused by DAVF from that caused by IIH except that patients with DAVF would less likely be young, female, and overweight. Noninvasive vascular imaging will not adequately delin-eate the architecture of a DAVF. Digital subtraction angiography is necessary to show the features that allow definitive diagnosis, treatment planning, and risk stratifica-tion (13). Risk stratification is partially based on whether CVR is present. There are critical differences in the features of cavernous and noncavernous DAVFs. The normal angioarchitecture of the cavernous sinus typically includes multiple outlets, which may explain the relatively low incidence of CVR in cavernous DAVFs as compared with noncavernous DAVFs (14). Satomi et al (15) classified cavernous DAVFs based on change in drainage pattern following thrombosis of the venous outlets. In a retrospective study of 65 cavernous DAVFs, these investigations showed that drainage initially was through the petrosal sinuses or the superior and inferior ophthalmic veins in 61 patients (Stages 1 and 2). As these outlets thrombosed, CVR became the drainage pattern (Stage 3), seen in only 4 patients. Cavernous DAVFs tend to close spontaneously more often than noncavernous DAVFs (16-18). FIG. 3. A. Right vertebral artery angiogram in anteroposterior projection performed before embolization demonstrates enlarged posterior meningeal artery (arrow) that shunts blood into right transverse-sigmoid sinus junction. B. Right external carotid artery angiogram in lateral projection demonstrates shunting into sigmoid and transverse sinuses (arrow). Reflux into cortical venous system is present (arrowhead). FIG. 4. A. After Stage 1 embolization, right external carotid artery (ECA) angiogram demonstrates persistent arterial feeder (white arrow), faintly seen ethylene vinyl alcohol (Onyx) cast (arrowhead), and persistent cortical venous reflux (black arrow), the reason for performing additional embolization. B. After Stage 2 embolization, right ECA angiogram demonstrates per-sistent cortical venous reflux (arrows), the reason for needing yet another embolization. C. After Stage 3 embolization, right ECA angiogram shows no residual arterial feeders or cortical venous reflux. Chaudhary et al: J Neuro-Ophthalmol 2014; 34: 259-263 261 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Noncavernous DAVFs are associated with significantly greater morbidity than cavernous DAVFs, perhaps because of the higher likelihood of having CVR (13,19,20). Untreated patients with DAVF associated with CVR are estimated to have a yearly incidence of 7% for hemorrhagic neurological deficit, 9%-13% for intracranial hemorrhage, and a 10% mortality rate (13,21,22). A recent report doc-umenting the natural history of 75 DAVFs with a 90-year follow-up (pooled data of total patient cohort) showed a doubling of the risk of hemorrhage if venous ectasia were added to CVR (14% with CVR alone and 27% with CVR and venous ectasia) (21). The strategy used in endovascular embolization of cavernous sinus and noncavernous sinus DAVFs differs. Fistulas of the cavernous sinus are typically fed by multiple arteries, including branches of the meningohypophyseal and ascending pharyngeal arteries. Embolization of these branches carries a substantial risk of cranial nerve palsies due to inadvertent occlusion of vasa nervorum (19,23,24). Because of their strong dural lining, DAVFs of the cavern-ous sinus can be approached transvenously, the preferred route. Transvenous embolization is performed effectively in DAVFs with coils (25,26). Liquid embolic agents such as EVOH are avoided because the inflammatory reaction gen-erated could result in cranial nerve damage. By contrast, the dural lining of the sagittal and transverse sinuses, the site of the papilledema shunt, is fragile enough to predispose to venous thrombosis if the shunting vein is approached endovascularly. The middle meningeal artery, the typical feeder of DAVFs located in the region of the transverse and sigmoid sinuses, can be readily cannulated with relatively low risk of cranial nerve damage and is the preferred route for treatment (23,27,28). Occluding the multiple feeding arterial branches often takes several hours. The duration of each embolization session must be limited to avoid overexposure to x-ray and contrast agents. Staged embolization is therefore employed when there are multiple feeders, as illustrated by our case. Treatment is considered successful when angiography shows complete elimination of all CVR. There are some reported small series of successful transvenous embolization (26,29), but we believe that the venous approach is hazardous because of the possibility of vessel rupture and extensive uncontrolled venous thrombo-sis. Moreover, arterial embolization helps to maintain nor-mal venous drainage through cortical veins into the large venous sinuses after shunt occlusion. Arterial embolization of noncavernous DAVFs with EVOH produces generally favorable outcomes. One series reported a 92% occlusion rate in patients not previously embolized (23). Carlson et al (28) reported continued occlu-sion of EVOH-treated DAVFs at angiography performed as far out as 4 months. There are also several short-term out-come reports of successful embolization of noncavernous DAVFs with EVOH (23,27-30). A total of 54 patients have been reported with angiographic obliteration. 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