Microsurgical obliteration of a high-flow intraorbital arteriovenous malformation fed by the ophthalmic artery: Illustrative case

Abstract

Background:

Intraorbital arteriovenous malformations (AVMs) are exceedingly rare high-flow vascular lesions that pose a direct threat to visual function through progressive proptosis, optic nerve compression, and retinal ischemia. When the ophthalmic artery (OA) constitutes one of the arterial feeders, endovascular embolization carries a prohibitive risk of permanent visual loss, making microsurgical resection the treatment of choice.

Case Description:

An 18-year-old female presented with progressive right-eye proptosis, complete ophthalmoplegia, and reduced visual acuity of 20/70. Multimodal imaging confirmed an intraconal AVM supplied predominantly by the OA. Given the unacceptable risk of retinal ischemia associated with OA embolization, the patient underwent microsurgical resection through a fronto-orbital craniotomy. Stepwise feeder-by-feeder devascularization achieved complete lesion obliteration with significant visual recovery and an excellent cosmetic outcome.

Conclusion:

Microsurgical resection is the definitive treatment for intraorbital AVMs when the OA is the dominant feeder and endovascular intervention is contraindicated. Operative success depends on adequate cranio-orbital exposure, disciplined feeder-by-feeder devascularization, and meticulous preservation of retinal perfusion throughout. Classification of the lesion according to the International Society for the Study of Vascular Anomalies framework guides triage and informs the risk-benefit analysis of each therapeutic modality.

INTRODUCTION

Intraorbital arteriovenous malformations (AVM) are rare congenital vascular anomalies defined by a direct high-flow shunt between arterial and venous channels through a dysplastic nidus that lacks an intervening capillary bed.[19,23] They are typically supplied by branches of both the internal and external carotid arteries and may present as isolated intraconal lesions – an exceptionally uncommon configuration – or in continuity with scalp and periorbital malformations.[13,21,23] Their true prevalence is unknown; however, under the modified International Society for the Study of Vascular Anomalies (ISSVA) classification, AVMs represent approximately 14% of all orbital vascular malformations (OVM), constituting the only high-flow subtype within this nosologically framework.[7,25]

The clinical course of orbital AVMs is variable. Patients may present acutely with sudden visual loss from hemodynamic decompensation, or more commonly with an indolent progression of proptosis, restriction of ocular motility, orbital pain, elevated intraocular pressure, and conjunctival injection.[14,23] Because these features overlap substantially with those of carotid-cavernous fistulas (CCFs), orbital cavernous venous malformations, and venous congestion secondary to remote intracranial AVMs, diagnostic precision is essential to avoid misclassification and inappropriate treatment.[6,7,16,24]

Management of intraorbital AVMs is technically demanding and must be individualized according to the angioarchitecture of the lesion, the identity of the dominant arterial feeder, and the degree of visual compromise.[1,10,17,23] When the ophthalmic artery (OA) constitutes the primary supply, endovascular embolization carries a well-documented risk of permanent retinal ischemia through inadvertent occlusion of the central retinal artery or posterior ciliary arteries.[9,12,20] In such cases, microsurgical resection represents the safest and most definitive therapeutic strategy.[1,19] We present an illustrative case of a high-flow intraconal AVM fed by the OA and terminal branches of external carotid artery, managed by microsurgical obliteration through a fronto-orbital craniotomy, with complete lesion obliteration and significant visual recovery.

CASE DESCRIPTION

An 18-year-old female with no relevant medical or family history presented to our neurosurgical service with a 6-month history of progressive, painless right-eye proptosis accompanied by worsening diplopia and blurred vision. On examination, Hertel exophthalmometry demonstrated 7 mm of axial proptosis of the right globe [Figure 1]. Neuro-ophthalmological assessment revealed complete ophthalmoplegia of the right eye with restriction of movement in all directions of gaze, and best-corrected visual acuity (VA) of 20/70 in the affected eye (20/20 in the left). Intraocular pressure was mildly elevated at 22 mmHg on the right. Fundoscopic examination showed mild disc edema without hemorrhage. There was no audible orbital bruit and no pulsatile component to the proptosis.

Figure 1:

Preoperative external photographs of the right orbit. The right eye demonstrates axial proptosis (7 mm by Hertel exophthalmometry), lower-eyelid fullness, and conjunctival congestion with a restricted, abnormally positioned globe consistent with complete ophthalmoplegia, whereas the left eye is normal. Both orbits for comparison.

Magnetic resonance imaging (MRI) of the orbits with gadolinium demonstrated a heterogeneous, avidly enhancing intraconal mass with flow voids consistent with a high-flow vascular lesion, located medial to the optic nerve and displacing it laterally [Figure 2]. Computed tomography angiography confirmed a compact nidus with early venous drainage into the superior ophthalmic vein (SOV). Digital subtraction angiography (DSA) of the internal and external carotid circulations bilaterally identified the OA as an arterial feeder, with contribution from external carotid branches [Figure 3]. There was no evidence of a CCF or intracranial AVM component. The lesion was classified as an orbital AVM under the modified ISSVA scheme.

Figure 2:

Preoperative magnetic resonance imaging of the orbital arteriovenous malformation (AVM). (a) Axial T1-weighted image after gadolinium shows a heterogeneous, avidly enhancing intraconal mass in the right orbit (white arrow), medial to the optic nerve and displacing it laterally, with associated proptosis and prominent contrast uptake consistent with an AVM nidus. (b) Axial T2-weighted image showing a flow-void signal within the right orbit (yellow arrow) and apex characteristic of a high-flow vascular malformation with no surrounding edema. (c) Coronal T1-weighted post-contrast image revealing the craniocaudal extent of the AVM with marked enhancement and dilated vascular structures within the right orbital region, with evidence of a partially thrombosed vein (orange arrow) demonstrating heterogeneous signal intensity, and no intracranial extension.

Figure 3:

Preoperative cerebral digital subtraction angiography (DSA) demonstrating the angioarchitecture of the orbital arteriovenous malformation (AVM). (a) Lateral projection of cerebral DSA following internal carotid artery injection demonstrating a markedly dilated ophthalmic artery (green arrow), consistent with arterial enlargement secondary to high-flow arteriovenous shunting within the orbital AVM nidus, with evidence of early venous return (blue arrow). (b) Anteroposterior projection demonstrating dual arterial supply to the AVM, with additional contribution from the external carotid artery system, notably through branches of the superficial temporal artery, indicating a complex, multi-pedicle angioarchitecture with both internal and external carotid arterial feeders supplying the nidus.

Given the implication of OA supply, the multidisciplinary team – comprising neurosurgery, interventional neuroradiology, and ophthalmology – determined that endovascular embolization carried an unacceptable risk of central retinal artery occlusion and permanent blindness.[9,12,20] Microsurgical resection was, therefore, selected as the primary treatment modality.

Surgical technique

The patient was positioned supine with the head fixed in a three-point Mayfield clamp, rotated 30° to the contralateral side and slightly extended to allow gravity-assisted frontal lobe retraction. A right-sided supraorbital-pterional craniotomy was performed using the technique described by Al-Mefty[2] providing simultaneous access to the anterior cranial base, the orbital roof, and the intraconal space. The temporal muscle was reflected anteriorly and inferiorly, and a single bone flap incorporating the orbital rim was elevated to maximize the working angle toward the orbital apex. The cranio-orbital exposure achieved with this approach, including the margins of the orbitotomy and the frontal and Sylvian dural folds, is illustrated in [Figure 4a].

Figure 4:

(a) Intraoperative view following right supraorbital-pterional cranio-orbitotomy demonstrating the surgical corridor: margins of the orbitotomy (yellow line), frontal dura (yellow arrow), and Sylvian dural fold (blue arrow). (b) On opening the periorbita, the orbital compartment was massively expanded by very high intraconal pressure, with mass effect from the arteriovenous malformation (AVM) nidus and markedly dilated, ectatic draining veins (black arrows) distorting the normal orbital anatomy. (c) Resection of the orbital roof toward the apex (black arrow) to widen the surgical corridor and decompress the congested soft tissue within the intraconal space. (d) Identification of the ophthalmic artery (blue arrow) on entering the orbit at the orbital apex. (e) Distal to the origins of small perforating branches, including the posterior ciliary and central retinal arteries, as well as the lacrimal artery, the ophthalmic artery continues as medial orbital branches (yellow arrow). (f) A major AVM feeding artery (yellow arrow) arising from the medial branch of the ophthalmic artery distal to the origin of the posterior ciliary and central retinal arteries – making it a safe site for proximal control. (g) Feeder-by-feeder devascularization: each feeding vessel (yellow arrows) was identified and isolated with a teardrop dissector, then coagulated and divided.

Following dural opening and gentle subfrontal retraction, the periorbita was incised along the orbital roof and the intraconal fat was carefully dissected under high-power microscopic magnification. On opening the periorbita, the orbital compartment was noted to be massively expanded by very high intraconal pressure, with mass effect from the nidus and markedly dilated, ectatic draining veins distorting the normal orbital anatomy [Figure 4b]. The orbital roof was resected toward the apex to widen the surgical corridor and decompress the congested soft tissue within the intraconal space [Figure 4c]. The nidus was identified as a compact, reddish-purple tangle of arterialized vessels with a characteristic thrill on palpation. The OA was identified at its origin from the internal carotid artery (ICA) and traced distally [Figure 4d]. The OA was then followed along its medial branch, with careful preservation of the small perforating branches – the posterior ciliary and central retinal arteries – as well as the lacrimal branch [Figure 4e]. A major feeding artery arose from this medial branch distal to the origin of the posterior ciliary and central retinal arteries, providing a safe site for proximal control, and gave rise to multiple feeders to the nidus [Figure 4f]. Feeding branches to the nidus were individually identified, temporarily occluded with micro-aneurysm clips, and confirmed to be non-retinal before permanent coagulation and division – a strict feeder-by-feeder devascularization sequence designed to prevent inadvertent sacrifice of the central retinal artery or posterior ciliary arteries [Figure 4g].

Once all feeding vessels were secured, the draining vein into the SOV was coagulated and divided, and the nidus was resected en-bloc. Meticulous hemostasis was achieved, the periorbita was closed, the bone flap was replaced, and the wound was closed in anatomical layers. The complete intraoperative sequence – from exposure of the surgical corridor to identification, isolation, and division of each feeding vessel – is documented in the intraoperative photographic series [Figure 4a-g].

Postoperative course

The patient was extubated uneventfully and transferred to the intensive care unit. Immediate postoperative examination demonstrated resolution of proptosis and improvement in ocular motility. VA improved in the right eye by postoperative day 3. Postoperative MRI confirmed complete resection of the nidus with no residual flow voids. DSA performed at 72 h confirmed complete angiographic obliteration of the AVM with no residual shunting and preserved OA patency [Figure 5]. The patient was discharged with no new neurological deficits. At 3-month follow-up, VA had further improved to 20/25, proptosis had fully resolved, and extraocular movements were intact in all directions [Figure 6]. Cosmetic outcome was excellent with no visible temporal hollowing or orbital asymmetry [Figure 7].

Figure 5:

Postoperative digital subtraction angiography at 72 h. (a) Lateral internal carotid artery injection confirms complete obliteration of the AVM with no residual nidus or early venous shunting and a preserved ophthalmic artery. (b) Lateral external carotid artery injection shows no abnormal filling, confirming the absence of recruited external carotid supply.

Figure 6:

Postoperative magnetic resonance imaging (a: axial view; b: coronal view) shows no residual AVM nidus.

Figure 7:

Postoperative photograph of the face showing excellent cosmesis.

DISCUSSION

Intraorbital AVMs are among the rarest entities in orbital surgery, and their management remains challenging due to the limited published experience and the high anatomical complexity of the orbital compartment.[10,18,23] The present case illustrates several features that are characteristic of this lesion type and that directly informed the therapeutic decision-making.

First, the clinical presentation – progressive proptosis, ophthalmoplegia, and reduced VA in a young patient without trauma or prior intervention – is consistent with the natural history of orbital AVMs as described in the literature.[10,14,23] The absence of a bruit and the non-pulsatile character of the proptosis, while atypical for a high-flow lesion, have been reported previously and should not exclude the diagnosis. The differential diagnosis in this setting must include CCF, orbital cavernous venous malformation, orbital varix, and venous congestion from a remote intracranial AVM draining through the SOV.[7,16,24] DSA remains the gold standard for definitive characterization of the angioarchitecture and identification of arterial feeders from both the internal and external carotid systems.

Second, the exclusive OA supply in this case is a critical determinant of treatment strategy. The OA is a terminal vessel supplying the retina through the central retinal artery and the choroid through the posterior ciliary arteries; occlusion of any of these branch’s results in irreversible visual loss.[9,12,20] Published series of trans-OA embolization for AVMs report devascularization rates of up to 73%, but at the cost of significant visual morbidity, including retinal artery occlusion and choroidal ischemia.[22] A case of complete blindness following n-butyl cyanoacrylate embolization of an orbital AVM through the OA has been reported, underscoring the gravity of this risk.[20] Stereotactic-guided direct puncture and transvenous approaches have been described as alternatives in selected cases[16] but were not applicable here given the compact intraconal nidus and the absence of a suitable transvenous access route.[4,16]

Third, the ISSVA classification provides a clinically useful framework for stratifying OVMs and guiding treatment decisions.[3,7,15,25] Under this system, orbital AVMs are distinguished from the more common low-flow lesions – cavernous venous malformations (OVM1, associated with somatic GJA4 gain-of-function mutations[8]), varices (OVM2), and infiltrating venous malformations (OVM3) – by their high-flow hemodynamics and the consequent risk of acute visual loss from arterial steal or venous hypertension.[5,25] Accurate classification is therefore not merely academic; it directly determines the urgency of intervention and the choice of therapeutic modality.

The supraorbital-pterional craniotomy, as described by Al-Mefty[2] and subsequently refined for cranio-orbital vascular pathology,[7,15] provided the necessary exposure to access the intraconal space from above while maintaining proximal control of the OA at its ICA origin. This approach is particularly well-suited to intraconal AVMs located at or near the orbital apex, where transconjunctival or lateral orbitotomy approaches offer insufficient working depth and limited proximal vascular control.[1] The transcranial orbitotomy has been independently validated for this indication in a recently published operative video report.[11]

CONCLUSION

The management of intraorbital AVMs fed by the OA distills to three operative imperatives. First, proximal vascular control must be established before nidus dissection. The supraorbital-pterional approach uniquely allows the surgeon to identify and temporarily occlude the OA at its ICA origin if needed, providing a critical safety margin during devascularization. Second, feeder-by-feeder devascularization – with preservation of retinal flow after each step – is non-negotiable. Premature venous occlusion before complete arterial disconnection risks acute nidus engorgement and intraoperative hemorrhage. Third, the central retinal artery and posterior ciliary arteries must be positively identified and preserved throughout; their sacrifice, even inadvertent, results in permanent blindness.

From a broader perspective, this case reinforces the principle that the treatment of orbital AVMs must be individualized and multidisciplinary. Endovascular embolization, while valuable as a preoperative adjunct when the external carotid artery provides the dominant supply, is contraindicated as a primary modality when the OA is the sole feeder. The goal of treatment extends beyond angiographic obliteration to encompass full functional recovery, including restoration of VA, resolution of proptosis, and preservation of extraocular motility – outcomes that are achievable with meticulous microsurgical technique, as demonstrated in this case.

Ethical approval:

The Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their images and other clinical information to be reported in the journal. The patient understands that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The author(s) confirms that they have used artificial intelligence (AI)-assisted technology for proofreading.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.