Endoscopic Endonasal Orbital Apex Decompression for Carotid Cavernous Fistula

Abstract

Significance Statement

This case report demonstrates a novel approach to treating a rare indirect carotid cavernous fistula (CCF) and associated abducens palsy. Although endovascular treatment is the standard of care in the management of CCFs, it was contraindicated in this patient. Instead, she underwent an endoscopic endonasal approach (EEA) with decompression of the medial orbital apex, including the cavernous sinus and optic nerve, with complete resolution of headache, lateral gaze palsy, and diplopia within 2 months.

Rhinoscopic Clinic

A 43-year-old female with a past medical history of migraines, hyperlipidemia, and rosacea presented to the hospital with a 1-week history of headache and vertigo, as well as a 2-day history of diplopia. She had no prior similar symptoms and no prior history of facial trauma or stroke. Initial imaging, including head computed tomography without contrast, was unremarkable. Ophthalmologic examination demonstrated 30° esotropia and a complete left abducens nerve palsy (Figure 1A). There was no loss of central, color, or peripheral vision.

Figure 1.

Extraocular movements. The extraocular function is shown in the primary, superior, inferior, and lateral gazes 1 week before (A), 1 week after (B), and 2 months after (C) surgery.

Cerebral angiogram showed a low-flow, indirect CCF from the meningohypophyseal trunk of the internal carotid artery (ICA) with backflow to the cavernous sinus through the superior petrosal sinus (Figure 2). Maximum medical treatment was attempted for 48 hours, which included timolol drops and high-dose steroid therapy; however, the patient showed no improvement of symptoms. Given the location and characteristics of the CCF, traditional surgical methods, including endovascular embolization, carried a high risk for complications including stroke and blindness. To alleviate the symptoms, the patient underwent surgical decompression of the left cavernous sinus, orbital apex, and optic canal via EEA with the assistance of intraoperative navigation.

Figure 2.

Preoperative cerebral angiogram. the left internal carotid artery (ICA) angiography is shown in the lateral view, with posterior to the left hand of the reader, anterior to the right hand of the reader, superior up, and inferior down. A dural arterial-venous fistula arises from the meningohypophyseal trunk of the ICA with backflow to the cavernous sinus. The black arrow shows the fistulous arterial branches of the meningohypophyseal trunk of the ICA. The black asterisk marks the fistulous venous pouch of the superior petrosal sinus, which is thrombosed. The white asterisk shows the normal vascular anatomical origin of the left ophthalmic artery.

During the procedure, a left middle turbinate resection, total ethmoidectomy and wide maxillary antrostomy, and bilateral sphenoidotomies were performed to visualize orbital floor back to apex for landmarks. The left ICA, lateral opticocarotid recess, pterygoid canal, and foramen rotundum were identified. A standard endoscopic medial orbital decompression was performed by removing the lamina papyracea, leaving the periorbita intact initially to the orbital apex. The sphenopalatine artery was ligated and the pterygoid canal and Vidian nerve were identified. Following the Vidian nerve back to the lacerum segment of the carotid canal, the maxillary strut of the sphenoid was removed. We then further exposed the foramen rotundum and removed the bone overlying the cavernous sinus. The optic canal was thinned using a drill and blunt dissection with a Cottle dissector. With the entire apex decompressed, a free mucosal graft from the middle turbinate was applied to the sella and lateral orbital apex to provide cover for the cavernous sinus and carotid artery. There were no intraoperative complications.

Postoperatively, the patient showed immediate improvement in diplopia and lateral gaze restriction. On follow-up at one week, there was a complete resolution of the patient’s headache. She still had mildly restricted abduction in the left eye −0.5 (of a 0-4 scale), and her diplopia was only present in far leftward gaze (Figure 1B). On follow-up at 2 months, there was a complete resolution of the patient’s headache, diplopia, and left cranial nerve (CN) VI palsy (Figure 1C). The patient gave consent for the publication of the case report.

Discussion

Modern day interventional treatment paradigms for most CCFs rely on endovascular treatment, with identification and occlusion of the fistulous track while maintaining normal blood flow through the ICA. ¹ Selection of approach is guided by angiographic features, such as feeding vessels and venous drainage pattern. ^2,3 Unfortunately, indirect CCFs can have multiple arterial-venous connections, requiring multiple endovascular treatments and the risk of a residual fistula. ⁴ The standard surgical treatment for indirect CCFs not amenable to routine endovascular intervention has thus far not been proposed. We discuss endoscopic decompression as the sole treatment of an indirect CCF with cranial nerve sixth palsy with significant ophthalmologic improvement. We postulate ophthalmologic improvement may have occurred through bone removal adjacent to the medial cavernous sinus and optic canal, relieving compression of the abducens nerve and/or its microvasculature. ⁵ Decompression may additionally have altered flow and turbulence within the cavernous sinus, allowing self-thrombosis of the fistulous vessels. An additional possibility is that auto-thrombosis occurred with watchful waiting in the absence of surgical intervention. ¹ Given the immediate postoperative improvement in diplopia, we hypothesize direct decompression of the medial cavernous sinus improved either direct pressure on the abducens nerve within Dorello’s canal or relief of pressure on the nerve’s microvasculature was achieved. Future studies of this rare problem and the role of endoscopic decompression are indicated.