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Abstract
The Pipeline Embolization Device (PED) is a flow diverting stent used in the treatment of a wide variety of intracranial aneurysms. The device differs from traditional stents used in stent-assisted coil embolization in that it has a tighter lattice structure with smaller cell sizes designed specifically to disrupt blood flow into aneurysms rather than only to retain coils within aneurysms. While the PED has been shown to be safe and effective, it has a unique risk profile that includes side branch and perforator vessel occlusion. Side branch occlusion in particular has been noted in several articles to occur at a relatively high rate with coverage of the ophthalmic artery origin by the PED. In this series, we present two cases of ophthalmic artery occlusion after PED placement with reconstitution of flow via an endoleak.
- Aneurysm
- Complication
- Flow Diverter
- Stent
- Angiography
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Background
The Pipeline Embolization Device (PED; ev3 Endovascular, Plymouth, Minnesota, USA) is a flow diverting stent approved for the treatment of large or giant wide-necked intracranial aneurysms of the internal carotid artery (ICA) from the petrous to the superior hypophyseal segments.1 While it was initially targeted at ICA aneurysms that are not amenable to traditional stent-assisted coiling techniques, it has also been shown to effectively treat small aneurysms,2–5 ruptured aneurysms,6–8 dissecting aneurysms,9–11 and aneurysms of different vascular territories.12–15 The PED is designed to disrupt blood flow into the aneurysm while maintaining blood flow through the parent artery and into side branches and perforating vessels whose ostia are covered by the PED. Once the PED is in place, stagnation of blood within the aneurysm promotes thrombosis, and the parent vessel undergoes remodeling as the PED becomes endothelialized.16 ,17 While studies of blood flow dynamics have supported these assumptions18 and short-term and intermediate-term follow-up studies have demonstrated the PED to be generally safe and effective,17 ,19 ,20 its long-term safety compared with conventional endovascular treatment techniques has not been fully explored. As such, clinicians must be aware of the potential risks of PED placement, including side branch/perforator vessel occlusion,21–24 in-stent thrombosis,25 intimal hyperplasia,26 stent migration/shortening,26–29 and delayed subarachnoid and intraparenchymal hemorrhage.16 ,17 To the best of our knowledge, no cases of ophthalmic artery occlusion after PED placement with reconstitution of flow via an endoleak have been described. In this article, we report two such cases.
Case presentation
Case 1
A 45-year-old man with a history of traumatic brain injury in 1999 presented to our hospital with hearing loss. MRI showed no cause for the patient's hearing loss, but incidentally demonstrated a large aneurysm arising from the cavernous segment of the right ICA. CT angiography (CTA) and a diagnostic angiogram confirmed an irregularly shaped 17×8×10 mm aneurysm arising from the right ICA at the C3–C4 junction, with focal severe stenosis of the right ICA immediately proximal to the neck of the aneurysm (figure 1A, B). The aneurysm was subsequently treated with a PED, which required coverage of the ophthalmic artery origin immediately distal to the neck of the aneurysm. Control angiography following PED deployment demonstrated good wall apposition of the stent, stagnation of contrast material within the aneurysm, and robust flow through the right ophthalmic artery (figure 1C). Six- and 12-month follow-up angiograms demonstrated patency of the right ophthalmic artery with evidence of an endoleak communicating with the origin of the ophthalmic artery. Given the patient's lack of visual symptoms, we elected to observe the endoleak. The 3-year follow-up angiogram demonstrated interval complete obliteration of the native ophthalmic artery origin with supply to the ophthalmic artery arising entirely through the mature endoleak passing through the residual aneurysm (figure 1D, E). Injection of the right external carotid artery (ECA) demonstrated no collateral supply to the ophthalmic artery. Of note, the patient continues to report normal vision.
(A) Cerebral angiogram demonstrating a large aneurysm arising from the right internal carotid artery (ICA) at the C3–C4 junction immediately proximal to the origin of the ophthalmic artery (solid white arrows). (B) Three-dimensional rotational reconstruction demonstrating the lobulated aneurysm and its relationship to the ophthalmic artery. (C) Cerebral angiogram showing the aneurysm immediately after PED deployment with stasis of contrast within the aneurysm and patency of the ophthalmic artery. (D) Follow-up cerebral angiogram and (E) three-dimensional rotational reconstruction demonstrating occlusion of the native origin of the ophthalmic artery with reconstitution of the patent ophthalmic artery via an endoleak channel (dashed white arrows) passing through the residual aneurysm.
Case 2
A 69-year-old woman with a history of coronary artery disease presented to our institution with sudden onset of severe headache. Initial non-contrast head CT demonstrated no evidence of subarachnoid hemorrhage. Brain MRI and time-of-flight MR angiography demonstrated three distinct intracranial aneurysms, the most suspicious of which was a large right paraclinoid ICA aneurysm. The other two aneurysms included a small right middle cerebral artery trifurcation aneurysm and a small anterior communicating artery aneurysm. CTA and a diagnostic angiogram confirmed a 13×11×11 mm aneurysm arising immediately distal to the origin of the ophthalmic artery (figure 2A,B). No distinct neck was identified, and the ICA was circumferentially dysplastic at the level of the aneurysm. The aneurysm was treated with a PED, which required coverage of the ophthalmic artery origin. Control angiography following PED deployment demonstrated good wall apposition of most of the stent, with the proximal end of the stent not fully apposed due to it terminating in the middle of a curve (figure 2C). Stagnation of contrast material within the aneurysm and robust flow through the right ophthalmic artery were observed. Six- and 12-month follow-up angiograms demonstrated patency of the right ophthalmic artery with progressive thrombosis of the aneurysm. The 3-year follow-up angiogram demonstrated an endoleak arising from the proximal aspect of the stent supplying a residual patent portion of the aneurysm. Additionally, the native origin of the ophthalmic artery appeared to be obliterated, and a channel from the residual aneurysm lumen supplied the ophthalmic artery, which demonstrated delayed filling (figure 2D, E). Injection of the right ECA demonstrated no collateral supply to the ophthalmic artery. Of note, the patient reported no vision loss or retro-orbital pain.
(A) Cerebral angiogram demonstrating a large right paraclinoid aneurysm arising immediately distal to the origin of the ophthalmic artery (solid white arrows). (B) Three-dimensional rotational reconstruction demonstrating the aneurysm and its relationship to the ophthalmic artery. (C) Cerebral angiogram showing the aneurysm immediately after PED deployment with stasis of contrast within the aneurysm and patency of the ophthalmic artery. (D) Follow-up cerebral angiogram and (E) three-dimensional rotational reconstruction demonstrating occlusion of the native origin of the ophthalmic artery with reconstitution of the patent ophthalmic artery via an endoleak channel (dashed white arrows) that is also supplying the residual aneurysm. Ophthalmic artery filling is poor on the early arterial phase.
Discussion
Numerous studies have demonstrated the short-term and intermediate-term safety and efficacy of the PED.16 ,17 ,19 ,20 As such, the PED has become an appropriate first-line treatment for many types of intracranial aneurysms, and the complication rates have been shown to be generally low. While most of the complications have been well-documented, including cases of ophthalmic artery occlusion,21 no cases of ophthalmic artery occlusion with reconstitution of flow via an endoleak have been reported.
The two cases described in this paper are very similar in their presentation. In both cases the ophthalmic artery was widely patent with robust flow after initial PED deployment and no evidence of significant collateral supply arising from branches of the ECA. Endoleak development was gradually observed over a series of follow-up angiograms, and obliteration of the native ophthalmic artery ostium eventually occurred with flow into the ophthalmic artery being maintained through channels arising from the endoleak. Additionally, neither patient reported any deleterious effects on their vision. In case 1 the endoleak developed directly through the interstices of the stent whereas, in case 2, the endoleak developed from the proximal end of the stent that was not fully apposed to the wall.
Occlusion of covered side branches and perforator vessels, including the ophthalmic artery, has been discussed in several studies.21–24 Interestingly, ophthalmic artery occlusion has been shown to occur at a much higher rate than occlusion of other branches, as much as 25% of the time in one study.21 It has been suggested that this may relate to the fact that the ophthalmic artery typically has a rich collateral supply compared with other side branches, so small reductions in flow caused by covering the origin of the ophthalmic artery with a flow diverting stent may promote increased flow through collaterals while allowing the native ophthalmic artery ostium to close over time.21 In light of this assertion, the fact that neither of the patients described here demonstrated significant collateral flow to their ophthalmic arteries on injection of their ECAs may explain why flow into their ophthalmic arteries was maintained via an endoleak rather than their ostia simply closing over time.
Conclusion
While the treatment of appropriately selected intracranial aneurysms with the PED has been shown to be safe and effective, it is important to be aware of the potential fate of covered side branches, particularly the ophthalmic artery. Despite the fact that both of the patients discussed in this series reported no deleterious effects on their vision, their cases illustrate the importance of evaluating the ophthalmic artery and its collateral supply closely prior to and following coverage by a PED and close monitoring of patients' vision postoperatively.
References
Footnotes
Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All additional patient data are part of the patients' electronic medical records.