Comparison of the Risk of Oculomotor Nerve Deficits between Detachable Balloons and Coils in the Treatment of Direct Carotid Cavernous Fistulas

Discussion

Ever since the use of balloons for the treatment of DCCFs was described by Debrun et al⁵ and Serbinenko,⁶ transarterial balloon embolization has been the criterion standard treatment for most patients with DCCF. Higashida et al¹ reported preservation of the parent artery in 88% of patients with DCCFs treated by using detachable balloons; other authors have described a need for parent artery occlusion in as many as 20% of cases.^2,3 Technical difficulties are not uncommon and are related to the size of the fistula and the cavernous sinus. The fistula should be smaller than an inflated balloon but large enough to allow passage of a deflated or partially inflated balloon, and the CS should be large enough to accommodate an inflated balloon or balloons. Failure often occurs when the fistula orifice is too small to allow entry or when a large fistula is combined with a small CS, allowing retraction of the inflated balloon into the ICA.⁷ We previously developed a double-balloon technique for use in such difficult cases.⁸ In addition to these technical difficulties, complications related to detachable balloon embolization of DCCFs are not uncommon and include venous stasis, orbital congestion, cerebral ischemia (3%), cerebral infarction (4%), and permanent neurologic damage (3%).⁹ Third and sixth nerve palsy after balloon embolization has also been observed. Debrun et al¹⁰ reported a 20% incidence of transient oculomotor nerve palsy, which is usually attributable to sixth cranial nerve dysfunction.¹¹

For DCCFs that are not successfully treated with ICA preservation by using a detachable balloon, transarterial GDC embolization is an alternative treatment. In 1992, Guglielmi et al¹² successfully treated DCCFs by transvenous GDC embolization, and there have been several subsequent reports of transarterial GDC embolization of DCCFs with favorable results.^13–15 The advantages of using GDCs are the ability to control their placement and easy retrieval and repositioning or exchange if necessary. It is also technically easier to guide a microcatheter and microguidewire combination through a small fistula than a balloon. However, in some cases, the anatomy of the involved compartment of the CS may prohibit efficient and correct packing of coils, leaving a partially patent DCCF. Repeat embolization is, therefore, common in patients undergoing GDC embolization of DCCFs. Bavinzski et al¹⁴ reported a case of a DCCF treated with GDC embolization in which the patient developed a massive exophthalmos and had abducens palsy and a decrease in visual acuity 6 days after embolization, owing to thrombosis of the superior ophthalmic vein. Another disadvantage of the GDC is its cost. As noted above, in the past few years, there has been a lack of availability of detachable balloons worldwide; thus, the use of GDCs as the primary choice for the treatment of DCCFs has increased.

In this investigation, we found that the risk of oculomotor nerve deficit was significantly higher when using a detachable balloon than a GDC for the treatment of DCCF. A possible reason for the occurrence of oculomotor palsy may be overinflation or migration of the balloon, leading to direct compression of the cranial nerves. The structures within the CS are contained within a membranous structure, and the inferior and medial portions of the membranes are composed of periosteum and are continuous with the periosteal layer of dura covering the middle fossa and sella turcica. The superior and lateral portion of the membranes are continuous with the connective tissue sheaths of cranial nerves III, IV, and V and may indirectly affect the course of cranial nerve VI, which runs across the ICA and enters the superior orbital fissure beneath the ophthalmic division of the trigeminal nerve. Consequently, a space-occupying lesion or increased pressure within the CS, which can be caused by a tumor, a DCCF, a dural fistula, thrombosis, or a balloon, may compress or affect some of these structures. In contrast, a GDC is very pliable and adapts to the shape of the CS without exerting a significant mass effect on the cranial nerves.¹²

The average time between trauma and embolization for the 5 patients who developed oculomotor deficits after embolization was 94.0 ± 108.4 days, which was in between the averages for the balloon and coil groups. Oculomotor nerve deficit was noted immediately after the procedure in 3 patients and on the second day after embolization in 2 patients. Three patients recovered from oculomotor nerve deficit (60%), but the condition was still observed at 2 weeks after embolization in 2 patients and at 1 month after embolization in 1 patient. One patient had not recovered from the oculomotor deficit 3 months after embolization and was subsequently lost to follow-up; the other patient had not regained oculomotor nerve function by the 1-month clinical follow-up. This patient was angiographically cured after the first embolization with a detachable balloon but developed cranial nerve III and VI palsy. Recurrent symptoms of exophthalmos and conjunctival injection were noted 1 month after embolization, and recurrent DCCF was diagnosed and cured by endovascular trapping.

Transarterial n-BCA embolization of DCCFs has been reported to be an efficient treatment for DCCFs when a transarterial detachable balloon or GDC fails to seal the fistula; this procedure has the advantage of being relatively easy to deliver through a microcatheter, producing rapid induction of thrombosis and permanent occlusion after polymerization. Luo et al¹⁶ reported that 16.7% of patients who underwent n-BCA embolization experienced temporary impairment of cranial nerve function, which resolved completely in each case within 6 months. We did not include patients treated with n-BCA in this study because we were concerned that complications associated with n-BCA might confuse our conclusions. However, it is important to investigate the complications associated with n-BCA, especially if this procedure is routinely used for the embolization of DCCFs.

Finding no obvious differences in terms of patient characteristics, fistula location, procedure-related mortality/morbidity, or initial angiographic results between the 2 groups suggests that GDCs may be as feasible, effective, and safe for DCCFs as detachable balloons. However, we did not include long-term follow-up results in the statistical analysis because almost one-fifth of the patients included in this retrospective study were lost to follow-up after 3 months. This is a limitation of this study and further investigation is necessary.