Journal of Neuro-Ophthalmology, March 1995, Volume 15, Issue 1

Left Dural to Right Cavernous Sinus Fistula

Direct carotid-cavernous sinus fistulas that present with signs and symptoms contralateral to the arterial supply of the fistulas are not uncommon. We present a thoroughly documented case of a dural-cavernous sinus fistula with symptoms exclusively contralateral to the arterial source, a rarer entity. The patient presented with a red, proptotic right eye and a history of transient horizontal diplopia and a "feeling of fullness" in that eye. Magnetic resonance imaging (MRI) of the brain and orbits performed at another hospital had shown no abnormalities. Carotid angiography performed on the right side was normal; carotid angiography performed on the left side showed a dural-cavernous sinus fistula, with shunting from branches of the left external carotid artery directly to the right cavernous sinus. Orbital duplex color-flow sonography showed reverse flow in a dilated right superior ophthalmic vein. This unusual manifestation of a dural-cavernous sinus fistula offers insight into the pathophysiology of arteriovenous fistulas involving the cavernous sinus, and is a reminder that bilateral injections are required when performing carotid angiography to characterize these disorders.

journal of ~ Neuro- Ophthalmology 15( 1): 31- 35, 1995. © 1995 Raven Press, Ltd., New York Left Dural to Right Cavernous Sinus Fistula A Case Report Timothy J. Martin, M. D., B. Todd Troost, M. D., Lawrence E. Ginsberg, M. D., Charles H. Tegeler, M. D., and Richard G. Weaver, M. D. Direct carotid- cavernous sinus fistulas that present with signs and symptoms contralateral to the arterial supply of the fistulas are not uncommon. We present a thor­oughly documented case of a rfwra/- cavernous sinus fis­tula with symptoms exclusively contralateral to the ar­terial source, a rarer entity. The patient presented with a red, proptotic right eye and a history of transient hori­zontal diplopia and a " feeling of fullness" in that eye. Magnetic resonance imaging ( MRI) of the brain and or­bits performed at another hospital had shown no abnor­malities. Carotid angiography performed on the right side was normal; carotid angiography performed on the left side showed a dural- cavernous sinus fistula, with shunting from branches of the left external carotid artery directly to the right cavernous sinus. Orbital duplex color- flow sonography showed reverse flow in a dilated right superior ophthalmic vein. This unusual manifesta­tion of a dural- cavernous sinus fistula offers insight into the pathophysiology of arteriovenous fistulas involving the cavernous sinus, and is a reminder that bilateral in­jections are required when performing carotid angiogra­phy to characterize these disorders. Key Words: Arteriovenous fistula- Dural- cavernous si­nus fistula. Manuscript received December 2, 1993; accepted May 25, 1994. From the Departments of Ophthalmology, Neurology, and Radiology, Bowman Gray School of Medicine, Wake Forest University Eye Center, Winston- Salem, North Carolina, U. S. A. Address correspondence and reprint requests to Dr. Timothy J. Martin, Wake Forest University Eye Center, Medical Center Boulevard, Winston- Salem, NC 27157- 1033, U. S. A. Arterial- cavernous sinus fistulas may result from a direct communication between the intracavern-ous carotid artery and the venous channels of the cavernous sinus ( direct carotid- cavernous sinus fistula) or between the smaller meningeal branches from either the internal or the external carotid ar­teries and the sinus ( dural- cavernous sinus fis­tula). The direct fistula is often the result of trauma or rupture of an intracavernous aneurysm, and generally presents with sudden, marked signs and symptoms of orbital vascular engorgement. Dural-cavernous sinus fistulae are associated with gener­alized vascular disease ( 1), and may present with slowly evolving, subtle clinical signs. Grove ( 2) speculated that this disorder arises from congenital vascular abnormalities that become symptomatic due to alterations in blood flow caused by venous thrombosis. We report the case of a dural-cavernous sinus fistula fed by left dural arteries, which presented with exclusively right- sided signs and symptoms. Although this unusual manifesta­tion of findings solely contralateral to the arterial source has been reported for direct carotid-cavernous sinus fistulas, it is less common with dural- cavernous sinus fistulas. CASE REPORT A 64- year- old woman noted the gradual onset of redness in her right eye in December 1992. Within 2 weeks she developed a horizontal diplopia, which lasted for 1 week. At that point she had pulsatile tinnitus, and a " feeling of fullness" in the right eye. On January 7, 1993, she underwent mag­netic resonance imaging ( MRI) of the brain and orbits at an outside institution; the findings were read as normal ( Fig. 1). Concern about an arterial-cavernous sinus fistula prompted conventional 31 32 T. /. MARTIN ET AL. FIG. 1. Postcontrast axial T1- weighted ( 500/ 25) MR image shows normal- appearing cavernous sinuses ( arrowheads). Note that the right superior ophthalmic vein is not enlarged ( black arrow). The curvilinear hy-pointense structure posterior to the pituitary gland may represent a dilated posterior intercavernous si­nus ( white arrows). cerebral angiography at another institution on March 26, 1993: the right common, right external, and right internal carotid arteries were injected via a right femoral approach but showed no abnormal­ities ( Fig. 2). We first examined the patient on April 1, 1993: her best corrected visual acuity was 20/ 30 in the right eye and 20/ 20 in the left eye; she had no rel­ative afferent pupillary defect, her visual fields were full to confrontation, and her left eye ap­peared normal. In contrast, the conjunctival ves­sels were markedly dilated and tortuous in the right eye ( Fig. 3), and exophthalmos was present ( Hertel exophthalmometer measured 20 mm on the right and 15.5 mm on the left); ocular motility was normal. Slit lamp examination showed clear corneas, with normal anterior chambers, irides, and lenses bilaterally. Intraocular pressures were 28 mmHg in the right eye and 18 mmHg in the left eye with applanation tonometry. Applanation tonometry showed wide swings in the mires when measuring the intraocular pressure of the right eye, which were not evident when measuring the left eye. Auscultation identified a pulsatile bruit, heard best over the right temple. The optic nerves, maculas, vasculature, and periphery appeared normal bilaterally. Orbital duplex color- flow sonography was per­formed on the same day, using a 7.5- MHz trans- FIG. 2. ( A) Right internal carotid arteriogram, lateral view and ( B) right external carotid arteriogram, lateral view. No evidence of an arterial- cavernous sinus fistula could be identified. ; Neuro- Ophthnlmol, Vol. 15, No. 1, 1995 CAVERNOUS SINUS FISTULA 33 FIG. 3. External photographs of the patient on the day of her initial examination at the Wake Forest University Eye Center. Dilated conjunctival vessels are evident in the right eye, the left eye is nor­mal. ducer on a P- 700 Color Velocity Imaging system ( Phillips Ultrasound International, Santa Anna, CA). Study of the right orbit showed marked en­largement of the superior ophthalmic vein with flow in an arterial direction ( Fig. 4). Enlargement of the right ophthalmic artery also was identified. The left side was normal. These findings with or- FIG. 4. Axial color- flow B- mode image of the right or­bit, obtained on the day of initial consultation. An en­gorged right superior ophthalmic vein is identified ( ar­row), with high velocity flow in an arterial direction. ( The globe is outlined with arrowheads.) bital color- flow sonography suggested an arterial-cavernous sinus fistula ( 3). Left carotid arteriogra­phy was performed on April 23, 1993, showing a dural- cavernous sinus fistula fed by left external carotid branches ( Fig. 5). The left cavernous sinus did not opacify during the arterial phase, and there was immediate shunting of blood to the right cav­ernous sinus via the intercavernous sinuses. The right cavernous sinus did opacify, and there was obvious drainage anteriorly through a dilated su- FIG. 5. Left external carotid arteriogram, AP view. Nu­merous small feeders ( brackets) can be seen supply­ing the fistula, which does not opacify the left cavern­ous sinus. Instead, flow appears in the intercavernous sinus ( small arrowhead) and then in the right cavern­ous sinus ( large arrowhead). Finally, flow is seen in an enlarged superior ophthalmic vein ( small arrow), an­gular vein ( curved arrow), and facial vein ( large ar­row). } Neuro- Ophthahnol, Vol. 15, No. 1, 1995 34 T. ]. MARTIN ET AL. perior ophthalmic vein, as well as the angular and facial veins. Later sequences demonstrate normal filling of the left cavernous sinus, without evi­dence of thrombosis ( Fig. 6). There was minimal contribution to the fistula from the left internal ca­rotid artery. DISCUSSION This patient demonstrated many of the classic clinical signs and symptoms of an arterial-cavernous sinus fistula, including exophthalmos, pulsatile tinnitus, " arterialization" of the conjunc­tival vessels of the right eye, elevated intraocular pressure in the right eye, and a history of horizon­tal diplopia that may have represented transient sixth cranial nerve dysfunction ( 1,4,5), but the ini­tial ancillary studies did not support such a diag­nosis. MRI performed early in the course of the disorder was thought to be normal, despite the presence of striking clinical signs. Angiography performed only on the symptomatic side was un­remarkable, even in the face of worsening symp­toms. The suspected diagnosis was confirmed by orbital duplex color- flow sonography, which had shown marked abnormalities only of the right or­bit. Subsequent angiography on the left showed an unusual fistula originating from the left external carotid dural vessels, with immediate shunting through the intracavernous sinus to fill the right FIG. 6. Left carotid arteriogram, lateral view. Venous phase demonstrates normal filling of the left cavern­ous sinus { arrow) and connecting venous pathways, without evidence of thrombosis. cavernous sinus. Dilated intercavernous sinuses with MRI have been reported in carotid- cavernous sinus fistulas ( 6). In retrospect, our patient's orig­inal MRI study may indeed have demonstrated an enlarged posterior intracavernous sinus ( Fig. 1). There are many reported cases of direct carotid-cavernous sinus fistulas with signs predominantly or exclusively contralateral to the arterial source ( 7- 12). It has been theorized that contralateral flow is the result of thrombosis of the ipsilateral cavern­ous sinus and/ or its communicating venous chan­nels ( 7- 12). Although anecdotal reports exist, there is a scarcity of well- documented cases of exclu­sively contralateral flow in dural- cavernous sinus fistulas ( 12). As with direct fistulas, thrombosis of the ipsilateral cavernous sinus is thought to be the mechanism by which blood is directed to the con­tralateral cavernous sinus via the intercavernous sinuses ( 12). In our patient, the blood was imme­diately and exclusively channeled to the right cav­ernous sinus via the posterior communication, de­spite normal patency and lack of identifiable thrombosis of the left cavernous sinus or associ­ated dural sinuses. These findings suggest that the position of the left arterial communication and its relation to venous channels in the cavernous sinus that communicate with the right cavernous sinus may be sufficient to explain this unusual flow in­dependent of thrombotic mechanisms. In summary, we have presented an unusual case of a dural- cavernous sinus fistula with manifesta­tions that were exclusively contralateral to the ar­terial supply. The case is instructive as contralat­eral flow appears to occur despite patency of ipsi­lateral cavernous sinus. The case also serves to reiterate the importance of injecting both the right and the left carotid systems in the angiographic exploration of suspected fistulas. REFERENCES 1. Miller NR. 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