Delayed Oculomotor Nerve Palsy After Coil Embolization of Carotid-Cavernous Fistula: Case Report and Literature Review

Dear Editor,

Carotid-cavernous fistula (CCF) is an acquired arteriovenous shunt between the internal or external carotid arteries and the venous channels of the cavernous sinus.¹,² Patients with CCF can present with various symptoms and signs such as headache, diplopia, blurred vision, and proptosis.¹,² Transvenous embolization (TVE) is the primary option for endovascular CCF treatment due to its safety and efficacy in obliterating the fistula, but it can occasionally induce several complications including venous congestion, sinus perforation, and ocular motor nerve palsy.³,⁴ Ocular motor nerve palsy mostly occurs immediately after a TVE procedure, and while delayed onset has been rarely reported in this disease, most of the reported cases had abducens nerve palsy.⁵,⁶,⁷,⁸

We describe a unique patient who presented with delayed isolated oculomotor nerve palsy at 8 years after successful coil embolization of CCF, and review the literature along with analyzing the clinical features of 11 additional patients.

A 45-year-old female presented with diplopia 8 years previously. She had conjunctival injection, exophthalmos, and oculomotor nerve palsy of the right eye for 1 week, and was diagnosed as indirect CCF. She received TVE for CCF, which completely resolved her symptoms and signs. She then developed ptosis of the right eye and diplopia 9 months previously. A neurological examination revealed a partial oculomotor nerve palsy that was affecting the pupil, and lid lag in the right eye (Fig. 1A). The prism cover test excluded the presence of right abducens nerve palsy. Laboratory evaluations for thyroid disease, myasthenia gravis, and other autoimmune disorders were unremarkable. Orbit MRI revealed dense embolization coils filling the right cavernous sinus (Fig. 1B), and cerebral angiography did not reveal any evidence of CCF recurrence (Fig. 1C). She did not receive specific treatment, and there was no improvement in the partial oculomotor nerve palsy 6 months later.

Fig. 1. The patient presented incomplete ptosis, mydriasis, and partial limitations of adduction, elevation, and depression to indicate a partial oculomotor nerve palsy, and lid lag in the right eye (A). Axial T1-weighted orbit MRI (B) and cerebral angiography (C) reveal dense embolization coils (arrow in B) in the right cavernous sinus without carotid-cavernous fistula recurrence.

Our patient presented isolated oculomotor nerve palsy 8 years after successful coil embolization of CCF. She presented development of oculomotor nerve palsy on the same side as the CCF, pupillary involvement with aberrant regeneration, was young without vascular risk factors, had no other systemic symptoms or abnormal laboratory evaluations for autoimmune disorders, and did not improve over 6 months. These factors supported a delayed complication of coil embolization of CCF rather than other diseases that cause oculomotor nerve palsy such as microangiopathy and autoimmune disorders.

A literature review revealed 11 additional cases with delayed ocular motor nerve palsy after successful coil embolization of CCF (Supplemental Table 1 in the online-only Data Supplement).⁵,⁶,⁷,⁸ The incidence of delayed ocular motor nerve palsy has ranged from 0.8% to 5.5%. Isolated abducens nerve palsy was present in 9 of the 11 cases, and the remaining 2 had abducens and partial oculomotor nerve palsies at 3–65 months after the TVE procedure. Delayed ocular motor nerve palsy resulted in permanent deficits in all of the cases. Remarkably, our patient presented with isolated oculomotor nerve palsy 8 years after successful coil embolization of CCF, which has not been described previously.

A plausible mechanism for delayed ocular motor nerve palsy after TVE is direct compression by the coil mass.⁵,⁶,⁷,⁸,⁹ This hypothesis can explain why most of the reported cases presented delayed abducens nerve palsy. Since the abducens nerve runs in the narrow lateral compartment of the cavernous sinus and runs freely rather than within the dura mater leaves of the cavernous sinus, it is more prone to injury due to a local mass effect. Lid lag due to aberrant regeneration and mydriasis supported the presence of chronic direct compression in our patient.

Thrombus formation is another possibility.⁵,⁶,⁷,⁸,⁹ The coils form a thrombophilic nidus for clot formation that is not resolved by fistula closure. Actually, excessively packing the cavernous sinus with coils can lead to postoperative cranial nerve palsies, and patients who had denser coil packing in the lateral portion of their cavernous sinus were more likely to develop abducens nerve palsy.⁵,⁹ However, this assumption can hardly explain the new development of ocular motor nerve palsy after complete resolution of an initial ocular motor nerve palsy via TVE.

Availability of Data and Material

The datasets generated or analyzed during the study are available from the corresponding author on reasonable request.

Supplementary Materials

The online-only Data Supplement is available with this article at https://doi.org/10.3988/jcn.2022.0351.

Supplementary Table 1

Summary of clinical findings in 12 cases with delayed OMNP after TVE of CCF