Objective:Retrograde cannulation of the superior ophthalmic vein(SOV) is an important route for embolization of cavernous sinus dural fistulas(CDF) .We present our experience with technically difficult cases in which it was not possible to isolate or cannulate this vein.Design:Retrospective,noncomparative,interventional case series.Patients:All patients diagnosed with dural CDF at the University of California Los Angeles Medical Center between January,1993,and July,2005,and who were treated with embolization via the SOV.Methods:The clinical records of all patients were reviewed.Main Outcome Measures:Patient demographics,clinical presentation,and surgical findings.Results:Of 91 patients diagnosed with CDF during the study period,25 patients(16 females,9 males;mean age,59 years) were treated with embolization via the SOV.In 6 of them(24% ;4 women and 2 men;mean age,67 years) ,there were significant difficulties in cannulation of the SOV or in successful closure of the fistula with this approach.Three patients had a fragile or a very small vein that could not be cannulated,and 1 of the 3 also had a large,posteriorly located varix that bled extensively on attempted cannulation.In 2 other patients,the anterior segment of the SOV was clotted and the catheter could not be threaded.In 1 patient,an inferior location of the supraorbital vein resulted in difficulties in correct identification of the SOV.Conclusions:Although the SOV is a useful route for CDF embolization,the presence of fragile or clotted veins can preclude successful cannulation.Deeper orbital dissections carry a higher risk of uncontrolled bleeding and should be avoided,especially in older patients with fragile veins and those with recently diagnosed high-flow fistulas. Objective: Retrograde cannulation of the superior ophthalmic vein (SOV) is an important route for embolization of cavernous sinus dural fistulas (CDF) .We present our experience with technically difficult cases in which it was not possible to isolate or cannulate this vein. Design: Retrospective, noncomparative, interventional case series. Patients: All patients diagnosed with dural CDF at the University of California Los Angeles Medical Center between January, 1993, and July, 2005, and who were treated with embolization via the SOV. Methods: The clinical records Of all patients were reviewed. Main Outcome Measures: Patient demographics, clinical presentation, and surgical findings. Of 91 patients diagnosed with CDF during the study period, 25 patients (16 females, 9 males; mean age, 59 years) were treated with 24 hours; 4 women and 2 men; mean age, 67 years), there were significant difficulties in cannulation of the SOV or in successful closure of the fistula with this a pproach.Three patients had a fragile or a very small vein that could not be cannulated, and 1 of the 3 also had a large, posteriorly located varix that bled extensively attempted cannulation. In 2 other patients, the anterior segment of the SOV was clotted and the catheter could not be threaded. 1 patient, an inferior location of the supraorbital vein resulted in difficult in correct identification of the SOV. Conclusions: Although the SOV is a useful route for CDF embolization, the presence of fragile or clotted veins can preclude successful cannulation. Deeper orbital dissections carry a higher risk of uncontrolled bleeding and should be avoided, especially in older patients with fragile veins and those with recently diagnosed high-flow fistulas.