Aneurysms that involve the internal carotid artery and posterior communicating artery junction and incorporate a fetal posterior cerebral artery are known as fetal posterior communicating artery aneurysms. We report the outcomes of four patients with fetal posterior communicating artery aneurysms who underwent treatment with the pipeline embolization device with or without adjunctive coil embolization. In our study, all four patients failed to achieve aneurysm occlusion at the last follow-up evaluation. Based on our results, we currently do not recommend the use of the flow diverter for the treatment of fetal posterior communicating artery aneurysms.
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Aneurysms of the internal carotid artery (ICA) and posterior communicating artery (PCOMA) junction, commonly known as PCOMA aneurysms, are among the most frequently encountered cerebral aneurysms, comprising about 30% of all intracranial aneurysms and more than 50% of all ICA aneurysms.1–4 The incidence of the fetal posterior cerebral artery (PCA) variant is reported to be between 4% and 29%,5 ,6 and among PCOMA aneurysms, 10% are associated with a fetal PCA variant.7 The pipeline embolization device (PED) was originally approved by the US Food and Drug Administration for the treatment of intracranial aneurysms proximal to the PCOMA; however, since its approval, its use for the treatment of intracranial aneurysms in more distal locations has grown.
In this study, we report the outcomes of four patients with PCOMA aneurysms incorporating a fetal PCA who underwent flow diversion treatment with a PED.
We report the cases of four patients with fetal PCOMA aneurysms who underwent treatment with a PED. Each of the patients had a PCOMA aneurysm incorporating a fetal PCA (fetal PCOMA aneurysm) treated with a PED, and had at least 12 months of angiographic follow-up. A fetal PCA was defined as one with a primary supply from the ICA on angiography, with an absent P1 segment. Patients with PCOMA aneurysms occurring on the ICA separate from the fetal PCA were excluded. The study was approved by the local institutional review board (Pro00019619).
All patients were treated with dual antiplatelet therapy comprising 325 mg of aspirin daily and 75 mg of clopidogrel daily for 7 days prior to the procedure. The degree of P2Y12 inhibition and aspirin response were tested with VerifyNow (Accumetrics, San Diego, California, USA) on the day of treatment. An aspirin response unit value of ≤550 and a Plavix response unit value of ≤220 were considered to indicate an appropriate level of platelet inhibition for treatment. All procedures were performed under general anesthesia. Systemic heparin was used to achieve an activated clotting time of ≥250 s. To ensure robust proximal support, a triaxial system was used through femoral access in each case. This consisted of a 6 F shuttle sheath (Cook Medical, Bloomington, Indiana, USA) placed in the common carotid artery prior to the bifurcation, a 5 F Navien distal access catheter (Covidien Vascular Therapies, Mansfield, Massachusetts, USA) placed proximal to the neck of the aneurysm, and the delivery microcatheter for the PED.
Case No 1
An elderly patient initially presented with a subarachnoid hemorrhage from a large left fetal PCOMA aneurysm. After coil embolization as the initial treatment, the aneurysm recurred at 6 months (figure 1A–D). The patient was retreated with a single PED (3.75×20 mm) with no untoward events (figure 1E). A follow-up angiogram at 3 years, however, showed persistent filling of the recurrence with no significant change (figure 1F–H).
Case No 2
This elderly patient presented with an unruptured multilobulated left fetal PCOMA aneurysm (figure 2A–C). Given the irregular morphology of the aneurysm, the patient underwent coil embolization of the fundus of the aneurysm first followed by placement of two overlapping PEDs (each 4×12 mm) in the same setting (figure 2D). The follow-up angiogram at 18 months showed persistent filling of the base of the aneurysm (figure 2E, F), which was unchanged from the final angiographic run at the end of the initial treatment.
Case No 3
An elderly patient was found to have an incidental large right fetal PCOMA aneurysm after suffering from a fall (figure 3A). The patient underwent placement of two coils jailed against a 4.5×14 mm PED in the same treatment (figure 3B). The follow-up angiogram at 18 months showed coil compaction and filling of the base of the aneurysm (figure 3C–E).
Case No 4
An elderly patient presented with a large unruptured right fetal PCOMA aneurysm along with a wide neck right middle cerebral artery aneurysm (figure 4A–C). The middle cerebral artery aneurysm was treated with a 3.5×14 mm PED and the fetal PCOMA aneurysm was treated with two overlapping PEDs (5×25 mm followed by a 5×20 mm) in the same setting (figure 4D). The follow-up angiogram at 18 months demonstrated persistent filling into both aneurysms with little change (figure 4E, F).
Treatment of PCOMA aneurysms incorporating the origin of the fetal PCA deserves special attention because of a higher treatment risk. Unlike in the non-fetal circulation where occlusion at the ostium will likely be asymptomatic because of ipsilateral P1 collaterals, injury or occlusion of the fetal PCA may result in occipital infarcts as well as midbrain or thalamic infarct if perforators were involved. Traditionally, fewer fetal PCOMA aneurysms than other PCOMA aneurysms were treated with endovascular therapy to avoid occlusion of the fetal PCA. More recently, balloon and stent-assisted techniques have made the treatment safer by reducing the risk of coil herniation into the fetal PCA lumen. With the advent of flow diversion, the concept of partial coiling to protect the dome of the aneurysm and to reduce the risk of fetal PCA compromise followed by potential definitive treatment with flow diversion is attractive. Our series results suggest, however, that flow diversion for fetal PCOMA aneurysms is ineffective and does not lead to aneurysm occlusion.
A fetal PCA is an end vessel with no distal collaterals. The demand of this large vessel will maintain flow and patency even after placement of a flow diverter because of the pressure gradient across the ostium. This is unlike the case of the non-fetal PCA, which has significant distal collaterals through the ipsilateral P1 segment that can in turn oppose flow and neutralize gradient in the PCOM artery after the flow diverter is placed across the PCOMA ostium, leading to potential vessel and aneurysm occlusion.8 It follows then that the part of the fetal PCOMA aneurysm incorporating the origin of the fetal PCA or close to it will remain patent, as seen in all of our cases. All patients at the final follow-up were taking only 81 mg of aspirin daily (since their 6 month follow-up), thus eliminating the effect of dual antiplatelet therapy as a contributing factor to aneurysm patency.
The main limitation of our study is the small number of patients with fetal PCOMA aneurysms. We are confident, however, that the minimum follow-up of 18 months represents sufficient time to assess aneurysm occlusion, as most studies with flow diversion use a 1 year angiographic result to define success or failure. Another concern is that three of our patients received either concomitant or previous coil embolization of the dome of the aneurysm, making it hard to draw conclusions on the efficacy of flow diversion on the dome of fetal PCOMA aneurysms; however, in the last case, flow diversion was performed without coil embolization and there was no change in the dome of the aneurysm at the last follow-up.
Based on our observations, we do not recommend the use of flow diversion for treatment of fetal PCOMA aneurysms. It appears not only to be ineffective for complete aneurysm occlusion, but it also limits future surgical and intrasaccular treatment options.
Contributors Each of the authors contributed substantially to this paper. Study design, data acquisition, data analysis and interpretation, and editorial revisions were done by all of the authors. PK completed the literature review. The manuscript was prepared by PK, ED, AP, and AW. All authors approved the final version.
Competing interests None declared.
Ethics approval The study was approved by the institutional review board of Baylor College of Medicine (Pro00019619).
Provenance and peer review Not commissioned; externally peer reviewed.
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