Endovascular intervention was planned, but by the time it was to occur 2 weeks later, the patient had experienced spontaneous improvement of all clinical manifestations. Examination now demonstrated visual acuities of 20/30 in both eyes, no afferent pupillary defect, intraocular pressures of 16 mmHg bilaterally with no medications, normal ocular motility and alignment, and a normal retinal examination. TRICKS MRA demonstrated resolution of the CCF (Fig. 6).
These 2 patients are remarkable for the fact that dural CCFs gave rise to optic neuropathy and sufficiently severe orbito-ocular manifestations to prompt consideration of endovascular intervention. In the interval between the intent and the readiness to intervene, however, the patients' clinical manifestations dramatically improved, so that no procedures were necessary.
The florid and vision-threatening manifestations displayed by our patients are uncommon in dural CCF (2,5,11,12). Optic neuropathy, present in both of our patients, was reported in 13% of 80 patients with dural CCFs (13). Our first patient developed almost complete ophthalmoplegia, angle closure, and elevated intraocular pressure. We found only 1 case report (9) describing angle closure from choroidal detachment in dural CCF. Choroidal detachment in dural CCF has only been described in 3 cases (9,10,14).
The main clinical indication for endovascular treatment of dural fistulas is progressive visual loss, with other possible indications being intractable headache, elevated intraocular pressure refractory to medication, diplopia, or an intolerable cosmetic deformity (2-4). The indications for therapy found on neuroimaging include the presence of a pseudoaneurysm, large varix of the cavernous sinus, venous drainage to cortical veins, and thrombosis of venous outflow pathways distant from the fistula (15).
Endovascular intervention is usually successful in closing a dural CCF. In a review of 133 patients with dural CCFs, Meyers et al (3) showed that 97% had good recovery and 90% achieved complete cure. Such intervention may, however, be complicated by allergic dye reactions, impairment of renal function, cranial nerve palsy, and stroke (11).
In the diagnosis of CCF, digital subtraction angiography (DSA) has been the gold standard. This study permits temporal resolution, which allows dynamic visualization of feeding arteries, venous drainage patterns, and assessment of flow rate, factors that are important not only for definitive diagnosis but also for management strategies. The drawbacks of DSA are its invasive nature and associated complications (22). Several time-resolved MRA techniques have been introduced to allow acquisition with temporal resolution simulating DSA (23-25). One such technique, TRICKS (24), was used in both of our patients to define the location and flow characteristics of the fistula.
The form of TRICKS we used provides a whole-head 3-dimensional image at a frame rate of approximately 1 image every 2 seconds. This magnetic resonance technique exploits several data acquisition and reconstruction concepts, including variable rate k-space sampling, temporal interpolation, and zero-filling in the slice dimension (24). This allows more rapid sampling of data and temporal resolution beyond the capabilities of conventional MRI and MRA, which provide only static images. TRICKS allows dynamic visualization of contrast bolus passage from arterial to venous phases, helping to detect vascular lesions that might remain occult on static MRI or CTA. In CCF, TRICKS provides assessment of fistulous sites of early venous filling and venous drainage rates, useful in predicting outcome and directing management. Other advantages are relatively high signal-to-noise-ratio and data acquisition in any orientation, independent of direction and rate of flow (24). TRICKS has also been useful in the imaging and management of arteriovenous malformations and tumors with high flow rates such as hemangiopericytomas (26-28).
We thank Dr. Iqbal Ahmed, Department of Ophthalmology, University of Toronto, for providing the images of the Visante OCT and ultrasonic biomicroscopy.
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