Anterior Cerebral Artery (A1 Segment) Aneurysm: Giant Partially Thrombosed A1 Aneurysm with Mass Effect, Treated with a Pipeline Embolization Device, Complete Resolution of the Mass Effect, and Modification of the Shape of the Implant During Long-Term Follow-Up

  • Rene VisoEmail author
  • Ivan Lylyk
  • Nicolas Perez
  • Esteban Scrivano
  • Pedro Lylyk
Living reference work entry


A giant A1 aneurysm exerting mass effect which was displacing both A1 arteries was found in a 64-year-old male patient who had presented with headaches and diplopia. The patient was treated with a Pipeline Embolization Device with good clinical and angiographic outcomes, with the singularity that the device changed shape as the mass effect from the aneurysm diminished. Actually, management of unruptured giant intracranial aneurysms is a matter of controversy among the neurovascular community. Several endovascular strategies have been used, such as stent-assisted coiling, flow diversion, and flow diversion and coils, with varying occlusion and complication rates reported. In this chapter, we present a case which shows the feasibility of using just one flow diverter stent as a sole treatment method for giant aneurysms. The various therapeutic options for treating of giant aneurysms are the main topic of this chapter.


Anterior cerebral artery ∙ Flow diversion ∙ Pipeline embolization device ∙ Giant aneurysm 


A 64-year-old male patient, a former smoker with a medical history of high blood pressure, who had experienced diplopia and headaches for 2 months prior to hospitalization.

Diagnostic Imaging

Brain MRI showed a giant, partially thrombosed aneurysm with an “onion skin” appearance inside the thrombus. This was exerting mass effect, resulting in partial compression of the third ventricle and mild ventricular dilatation. Subsequent DSA confirmed this right A1 aneurysm, with its mass effect displacing both A1 segments in a tent-like fashion (Fig. 1).
Fig. 1

Diagnostic MRI/MRA and DSA showing a right-hand partially thrombosed A1 aneurysm. Axial T2WI (a), coronal T2WI (b), and axial contrast-enhanced T1WI (c) MRI show the layered structure of the intra-aneurysmal thrombus, the thick aneurysm wall, and cysts forming adjacent to the aneurysm (asterisk). Note the elevation of the A1 segment of the right ACA (arrow). DSA in posterior-anterior projection (d) and working position (e) and rotational DSA with 3D reconstruction (f)

Treatment Strategy

The primary goal of the treatment was to stop the aneurysm growing any further and thus improve the clinical symptoms coming from the mass effect and aneurysm pulsation, caused by the blood flow entering the aneurysm. Preventing a possibly fatal aneurysm rupture was a secondary goal. Microsurgical clipping was considered to be both challenging and potentially hazardous. Coil or WEB occlusion of the non-thrombosed part of the aneurysm would have been possible but would have been followed by a migration of the coils or WEB inside the thrombus, resulting in endless retreatment sessions. Therefore, flow diversion using a pipeline embolization device (PED) to perform an endovascular vessel reconstruction was considered to be the most promising strategy.


Procedure, 09.12.2010: endovascular treatment of a giant, partially thrombosed aneurysm of the right A1 segment by implanting a PED

Anesthesia: general anesthesia: 10,000 IU unfractionated heparin (Riveparin, Rivero) IV

Premedication: 1× 100 mg ASA (Aspirin, Bayer Vital) PO daily and 1× 75 mg clopidogrel (Troken, Laboratio Bagó) PO daily starting 5 days before the intervention

Access: right femoral artery, 7F sheath (Terumo); guide catheter: 6F Envoy (Cordis); microcatheter: Renegade 27 (Boston Scientific); microguidewire: Transend 0.014″ (Stryker)

Implants: Pipeline Embolization Device 3/18 (Medtronic)

Course of treatment: the right internal carotid artery was catheterized with a 6F Envoy guide catheter. A Renegade 27 microcatheter with a 0.014″ microguidewire was navigated cautiously to the A2 segment of the right anterior cerebral artery. Then, a pipeline embolization device 3/18 mm was deployed from the right A2 to the right A1 segment, covering the aneurysm neck. A significant change in flow inside the aneurysm was seen once said device had been deployed (Fig. 2).
Fig. 2

Endovascular treatment of a giant, partially thrombosed right A1 aneurysm. DSA images in the working projection after the device was deployed at neck level (a, b). After the PED had been deployed, the flow inside the aneurysm immediately changed. Note the final configuration of the PED due to the mass effect of the intra-aneurysmal thrombus, displacing the right A1 segment

Duration: 1st–12th DSA run: 52 min; fluoroscopy time: 21 min

Complications: none

Post medication: 1× 100 mg ASA PO daily for life, 1× 75 mg clopidogrel for 6 months

Clinical Outcome

The procedure was well tolerated, and the patient was discharged home without any neurological deficit 2 days later. The patient remained asymptomatic at the 7-year follow-up, with a modified Rankin Scale of 0.

Follow-Up Examinations

Follow-up MRI/MRA at 6 months, 12 months, and 7 years showed progressive shrinkage of the thrombus (Fig. 3). DSA at 6 months confirmed the complete occlusion of the aneurysm and that the mass effect on the A1 segment had decreased. At the 12-month and 7-year follow-up DSAs, the aneurysm remained occluded, and the mass effect on the A1 segment continued to decrease (Fig. 4, 5, and 6).
Fig. 3

Follow-up MRI/MRA of a patient with a giant right-hand A1 aneurysm treated with a PED. Axial T2WI (a, d, g), coronal T2WI (b, e, h), and axial T1WI (c, f, i) at 6 months, 12 months, and 7 years showed progressive shrinkage of the thrombus

Fig. 4

Follow-up DSA of a giant and partially thrombosed right-hand A1 aneurysm treated with a flow diverter stent. DSA with posterior-anterior projection (a, c, e) and the previous working projection (b, d, f) at 6 months (a, b), at 12 months (c, d), and at 7 years (e, f). VasoCT showed the calcification of the aneurysm wall (g). As the aneurysm progressively shrank, the right A1 segment containing the PED, which was still bent at 6 months due to mass effect exerted by the aneurysm (b), straightened once the intra-aneurysmal thrombus had disappeared (f). It is noteworthy that the calcification of the aneurysm wall did not prevent the aneurysm from shrinking

Fig. 5

Follow-up DSA with simultaneous injection of both ICAs. Immediate posttreatment DSA in posterior-anterior projection (a), DSA follow-up at 12 months (b) and at 7 years (c). Note the modification of the vessel’s course. The initial tent-shaped configuration of both ACAs has disappeared, the course of both ACAs has returned to normal, and the vascular diameter of the left A1 segment has significantly increased. This is all due to the flow demand of the left ACA increasing once the A1/A2 connection on the right-hand side had been covered by the PED

Fig. 6

Modification of the PED shape as the mass effect of the giant A1 aneurysm diminished. Immediately after deployment (a), at 3 months (b), at 12 months (c), and at 7 years (d). The shape of the PED straightened to copy the changed course of the right-hand A1 segment


Giant intracranial aneurysms are defined as aneurysms with a fundus diameter of 25 mm or more. They represent 5% of all intracranial aneurysms and commonly become symptomatic in patients between 40 and 70 years old. Two-thirds of giant aneurysms are located in the anterior circulation (Lonjon et al. 2015).

The treatment of large and giant intracranial aneurysms is complex due to the high rate of morbidity in open surgery and the low rate of endovascular efficacy previous to the era of flow diverter stents (Szikora et al. 2013). The endovascular treatment of giant aneurysms using flow diverter stents has provided a high rate of fully and stably occluded aneurysms that were considered uncoilable (Becske et al. 2013).

Giant aneurysms carry a significant risk of hemorrhage, reported as a 40% 5-year cumulative rupture rate for the anterior circulation and 50% for the posterior circulation (Wiebers et al. 2003). Non-ruptured giant aneurysms often present with mass effect (e.g., cranial nerve palsy, hydrocephalus, or epileptic seizures). The clinical presentation depends on the anatomical location of the aneurysm with symptoms depending on what is being compressed. Therefore, the treatment goal is not only to prevent a potential rupture but also to reduce the transmitted pulsation and eliminate mass effect (Szikora et al. 2013).

Before flow diverters were a feasible option, the conventional approach in endovascular treatment had been to densely pack the aneurysm with soft coils in order to reduce the pulsation. However, this aim can only be achieved if the aneurysm neck is completely sealed. Due to the notoriously wide necks of these giant aneurysms, complete packing was frequently not achieved, resulting in a low rate of clinical improvement and a high rate of recanalization with frequent retreatments (Henkes et al. 2008; van Rooij and Sluzewski 2008). A surgical treatment approach was considered superior in cases of compression syndromes because of the immediate decompression of the neural tissue; however, in a report of 21 giant or large ophthalmic aneurysms which had been surgically treated, it was revealed that only 75% of patients experienced an improvement in their visual field (Dehdashti et al. 2012). One should also take into account that the recovery process of the pressure-related symptoms may be affected by multiple factors such as how long symptoms had been present before treatment, whether their onset had been acute or gradual, and the degree of cranial nerve impairment (van Rooij and Sluzewski 2008).

The use of flow diversion in treating intracranial aneurysms has been widely reported in previous studies with an occlusion rate of 95% at 12 months, and no future recanalization once an aneurysm has been occluded (Lylyk et al. 2009). In a trial comprising 107 patients, 78 out of 81 (96%) patients seen at a 5-year clinical follow-up had modified Rankin Scale scores of ≤2 (Becske et al. 2017). There may be a temporary aggravation of compression-related symptoms due to reduced flow in the aneurysm sac. This can induce an increased mass effect in the initial stage of the thrombosis and may require a high dosage of corticosteroids (Hammoud et al. 2003). A delayed rupture of an aneurysm following flow diversion due to instability of the intra-aneurysmal thrombus and wall degradation due to a rapidly growing thrombus with protease secretion is another serious risk (Kulcsár et al. 2011; Turowski et al. 2011).

In a report of 30 large and giant aneurysms which had only been treated by flow diversion, 90% of the aneurysms were completely occluded. In the remaining 10% of cases, the aneurysm shrank but did not fully disappear. In these reports, the rigid, calcified aneurysm wall was considered the cause behind the complete collapse of the aneurysm sac despite there being no remaining flow inside the sac. In the same report, all of the patients with completely occluded aneurysms experienced improvement in or even complete resolution of their nerve compression symptoms (Szikora et al. 2013). In a report by Zanaty et al. (2015), a total of 6/8 patients (75%) with large, intracranial partially thrombosed aneurysms showed complete angiographic occlusion with reduced thrombus and were no longer symptomatic. The other two patients experienced an increased thrombus despite complete angiographic occlusion. In a report by Piano et al. (2013), a total of 104 aneurysms treated with either SILK (Balt) or a PED had a complete occlusion rate of 86% at 6 months, with another 12% rated “subocclusion.” The aneurysm sac shrank in 61% of the aneurysms assessed. As illustrated by the case presented above and in line with several publications, flow diversion is a viable option for the endovascular treatment of selected large and giant intracranial aneurysms.



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Copyright information

© Springer Nature Switzerland AG 2020

Authors and Affiliations

  • Rene Viso
    • 1
    Email author
  • Ivan Lylyk
    • 1
  • Nicolas Perez
    • 1
  • Esteban Scrivano
    • 1
  • Pedro Lylyk
    • 1
  1. 1.Clinica La Sagrada Familia, ENERIBuenos AiresArgentina

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