C.M. Benson , D.M. Pelz and S.P. Lownie
Departments of Medical Imaging and Clinical Neurological Sciences
University Hospital
London, Ontario, Canada

In their recent publication “Parent Artery Occlusion in Large, Giant, or Fusiform Aneurysms of the Carotid Siphon: Clinical and Imaging Results,” Labeyrie et al¹retrospectively reviewed 56 patients treated with aneurysm trapping by using detachable platinum coils. The authors make 2 controversial statements, neither of which is referenced, and with which we take issue:

1. “Proximal occlusion without trapping (surgical or endovascular) has a lower rate of aneurysmal retraction and should not be performed for carotid aneurysms.”

2. “Endovascular parent artery occlusion with trapping of the aneurysm has long been considered the reference treatment for large, giant, or fusiform aneurysms of the carotid siphon.” [Italics added for emphasis.]

Several large series of giant aneurysms treated with parent artery occlusion have, in fact, demonstrated the safety and efficacy of this treatment alone. Even in the setting of initial retrograde filling, these aneurysms often progress to complete thrombosis. In 1994, Drake et al² published a series of 160 anterior circulation giant aneurysms treated with Hunterian proximal occlusion. Eighty of 82 petrous and cavernous aneurysms were obliterated with proximal occlusion, only 4 of which required trapping. In 1987, Fox et al³ reported 58 patients with anterior circulation giant aneurysms, with all 37 aneurysms below the ophthalmic segment and 10 of 21 supraclinoid aneurysms obliterated with proximal occlusion alone without the need for trapping. We have been unable to find evidence in the literature demonstrating the inferiority of proximal occlusion as a first-line procedure. Furthermore, the addition of distal occlusion may have contributed to the authors’ increased rate of ischemic events in 27% of patients, because the origins of perforating vessels will, by definition, be occluded across any trapped segment. We would argue that proximal occlusion of the parent artery without trapping remains a viable time-honored treatment option for giant saccular and fusiform carotid aneurysms.

References

1. Labeyrie MA, Lenck S, Bresson D, et al. Parent artery occlusion in large, giant, or fusiform aneurysms of the carotid siphon: clinical and imaging results. AJNR Am J Neuroradiol 2015;36:140–45 » Abstract/FREE Full Text
2. Drake CG, Peerless SJ, Ferguson GG. Hunterian proximal arterial occlusion for giant aneurysms of the carotid circulation. J Neurosurg 1994;81:656–65 » Cross Ref » Medline
3. Fox AJ, Vinuela F, Pelz DM, et al. Use of detachable balloons for proximal artery occlusion in the treatment of unclippable cerebral aneurysms. J Neurosurg 1987;66:40–46 » CrossRef » Medline

Reply

M.A. Labeyrie, J.P. Saint-Maurice and E. Houdart
Department of Interventional Neuroradiology
Lariboisière Hospital
Paris, France

We would like to thank Benson et al for their thoughtful reading of our recent work and their comments. We do agree with them that there is no evidence demonstrating the inferiority of proximal occlusion versus trapped occlusion of large or giant carotid aneurysms because there is no controlled study in the literature. Our 2 “controversial statements” certainly have to be nuanced because they reflect personal considerations based on our own (unpublished) practical experience of proximal occlusion.

The comparison between the series of Drake et al¹ and ours² has several limitations. If we consider this exploratory comparison, we observed similar rates of complete aneurysmal occlusion (99% versus 97% for cavernous and 74% versus 73% for ophthalmic aneurysms, respectively). However, in the series of Drake et al, an additional trapping was performed in 5% of patients with carotid cavernous aneurysms and in 21.7% of patients with ophthalmic aneurysms. The comparison of the severe morbidity rate is uncertain because the available outcome criteria are different in the series of Drake et al and ours. This rate may be 1.3% versus 2.5% (or 0% if we consider only patients with a modified Rankin Scale score of >2) for cavernous and 8.6% versus 14.3% (7% if we consider only patients with a modified Rankin Scale score of >2) for ophthalmic aneurysms, respectively. In the series of Drake et al, the mortality rate seems to be higher because we observed no death in our series. In the same series of Drake et al, the severe morbidity and mortality rates were equal to zero for both carotid cavernous and ophthalmic aneurysms if we consider only the proximal occlusions performed with detached balloons (including 19/63 [30%] extra-/intracranial bypasses).

We do not share the assumption of Benson et al that, “The addition of distal occlusion may have contributed to … the increased rate of ischemic events in 27% of patients [of our series], because the origins of perforating vessels will by definition be occluded across any trapped segment.” Actually, in our series, no perforating vessel was occluded with coils and no ischemic event was attributed to this mechanism because, “When the upstream segment was too short to set up coils, an occlusion of the aneurysm and of the parent artery was performed in opposition and downstream.”²Therefore, we do not think that this trapping technique presents a higher risk of adverse events compared with proximal occlusion alone. On the contrary, we consider that the trapping technique may have 2 potential (albeit unproven) benefits compared with the proximal occlusion alone, especially in carotid ophthalmic giant aneurysms. These potential benefits are the following:

1. To prevent a massive embolism coming from the occluded segment by trapping the thrombus (2.5%/0% of the carotid cavernous/ophthalmic aneurysms in the series of Drake et al¹ versus none in our series).

2. To prevent the risk of bleeding of the untrapped aneurysm until it is completely excluded from the arterial flow (no patients in the series of Drake et al¹ but several cases are reported in the literature³).

In conclusion, despite our personal preferences for proximal occlusion versus trapped occlusion, we can only share the opinion of Benson et al that “proximal—as well as trapped—occlusion of the parent artery without trapping remains a viable time-honored treatment option for giant saccular and fusiform carotid aneurysms.”

References

1. Drake CG, Peerless SJ, Ferguson GG. Hunterian proximal arterial occlusion for giant aneurysms of the carotid circulation. J Neurosurg 1994;81:656–65 » CrossRef » Medline
2. Labeyrie MA, Lenck S, Bresson D, et al. Parent artery occlusion in large, giant, or fusiform aneurysms of the carotid siphon: clinical and imaging results. AJNR Am J Neuroradiol 2015;36:140–45 » Abstract/FREE Full Text
3. Vincent F, Weill A, Roy D, et al. Carotid ophthalmic aneurysm rupture after parent vessel occlusion. AJNR Am J Neuroradiol 2005;26: 1372–74 » Abstract/FREE Full Text