Keywords

Patient

A 60-year-old female patient with a history of cigarette smoking of 35 pack years, type 2 diabetes mellitus, and high arterial blood pressure who presented with a headache and diplopia.

Diagnostic Imaging

On noncontrast CT (NCCT), CT angiography (CTA), and subsequent Magnetic Resonance Imaging (MRI), a large PcomA aneurysm was observed on the right hand side. The aneurysm was exerting mass effect on the right hippocampus. Diagnostic cerebral digital subtraction angiography (DSA) confirmed the presence of a large aneurysm arising from the inferior and middle aspects of the origin of the right-hand posterior communicating artery (PcomA) (Fig. 1).

Fig. 1
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Diagnostic imaging in a patient who presented with headaches and diplopia. Axial NCCT (a) showing a slightly hyperdense mass located in the suprasellar cistern. CTA (b) reveals the aneurysm. DSA shows the posterior-anterior (c) and lateral (d) view of the right hand ICA with the large PcomA aneurysm. Allcock maneuver (e) to visualize the right PcomA by manual compression of the right CCA and injection of the left VA. 3D DSA (g) showing the size of the aneurysm (height 18.6 mm, width 10 mm with a neck of 2.5 mm) and an aspect ratio of the height and neck of the aneurysm of 7.5 (f). 3D DSA measuring the angle between the parent vessel and the aneurysm at 78 degrees (h)

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Treatment Strategy

The primary goals of the treatment were to prevent an aneurysm rupture, reduce the aneurysm pulsation in order to improve the clinical symptoms, and, if possible, preserve the patency of the PcomA, accepting that the occlusion of the right PcomA in the presence of a right P1 segment would most likely be tolerated. Five days prior to the endovascular procedure, dual antiplatelet medication was initiated using aspirin and prasugrel. The treatment strategy was designed to preserve the PcomA, using an intrasaccular device to create a safety margin in the proximal part of the aneurysm neck so that the part of the aneurysm neck joined to the right PcomA would remain permeable. Equally, the device would support the coil cast when occluding the aneurysm sac. An issue was the choice of device due to the vascular anatomy of the patient, the sharp angle between the aneurysm neck and the parent vessel, which was about 78-degrees. The pCONUS2 (phenox) was chosen to treat this patient due to its articulating connection between the stent-shaft and the distal petals. The basic concept was an advanced mode of stent-assisted coil occlusion.

Treatment

Procedure, 02.09.2017: stent-assisted coil occlusion of a large right PcomA aneurysm using pCONUS2

Anesthesia: general anesthesia, 10,000 IU unfractionated heparin (Riveparin, Ribero) IV Premedication: 1× 100 mg ASA (Aspirin, Bayer Vital) PO daily, and 1× 10 mg prasugrel (Procardia Roemmers) PO daily, starting 5 days before the intervention

Access: right femoral artery, 8F sheath (Terumo); guide catheter: Shuttle 8F guide catheter (Cook); intermediate catheter: Navien A+ 0.072¨ (Medtronic); microcatheter: Excelsior SL-10 (Stryker) for coils; and Prowler Plus 0.021″ (Codman) for pCONUS2; microguidewire: Transend 0.014″ (Stryker).

Implants: stent: pCONUS2 4/15/10 mm (phenox); 5 coils: 1× XL 360° Standard 16/50, 1× Target 360° Standard 15/40, 1× GDC-18 360° Standard 14/30, 1× GDC-18 360° Standard 12/30, 1× GDC-18 360° Standard 10/30 (Stryker)

Course of treatment: after an 8F vascular sheath was placed into the right common femoral artery, the right internal carotid artery was catheterized and standard Towne’s lateral angiographic images and a rotational angiography with 3D reconstruction were acquired in order to determine the most suitable working projection. The aneurysm measurements were made using standard methods. The angle between the parent artery and the aneurysm sac was also calculated. After the angiography, an 8F Shuttle catheter was placed into the right common carotid artery and an intermediate Navien A+ 072 catheter was inserted into the petrous portion of the ICA. A Prowler Select Plus 0.021″ microcatheter was navigated and placed inside the aneurysm. The pCONUS2 device was deployed over the aneurysm neck and the crown with the six petals directed above the origin of the PcomA. A second microcatheter, an Excelsior SL-10, was inserted through the shaft of the pCONUS2 and through the petals into the aneurysm sac. During the coil embolization, the end of a spiral protruded through the device into the lumen of the ICA and repositioning became impossible. The pCONUS2 was not detached until the complete coil occlusion had been achieved. An NCCT was done after the procedure and no hemorrhagic or ischemic lesions were observed (Fig. 2).

Fig. 2
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DSA showing a pCONUS2 bifurcation stent-assisted coil occlusion of a PcomA aneurysm. Stent-assisted coiling was chosen despite the narrow aneurysm neck in order to preserve the patency of the right PcomA. Using a working projection (a) the correct placement and complete opening of the pCONUS2 device was verified by VasoCT (b, c); note the angle between the parent artery and the aneurysm sac. Complete coil occlusion of the aneurysm with preserved patency of the PcomA was achieved as intended (d, e)

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  • Duration:1st – 18th DSA run: 155 min; fluoroscopy time: 45 min

    Complications: none

  • Post medication: 1× 100 mg ASA PO daily for life and 1× 10 mg prasugrel PO daily for 3 months

Clinical Outcome

The procedure was well tolerated and the patient was discharged home without any new neurological deficit 2 days later.

Follow-Up Examinations

Follow-up DSA and MRI/MRA examinations after 1 year confirmed the complete occlusion of the aneurysm. The PcomA remained patent. No in-stent stenosis was observed (Fig. 3).

Fig. 3
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A 1-year follow-up MRI/MRA and DSA was performed. A complete aneurysm occlusion was confirmed and no stenosis or displacement of the device was seen while the PcomA remained patent. The diplopia resolved completely after the endovascular treatment

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Discussion

PcomA aneurysms are relatively common, accounting for 15–25% of all the intracranial aneurysms (Golshani et al. 2010; Matsukawa et al. 2014) and have a clear risk of subarachnoid hemorrhage because of their intradural location. The International Study of Unruptured Intracranial Aneurysms (ISUIA) trial included the PcomA aneurysm in the posterior circulation group and reported a 5-year cumulative aneurysm rupture rate of 18.4% for 13–24 mm aneurysms (Wiebers et al. 2003). Other authors report a risk of PcomA aneurysm rupture of 0.49% annually according to the size of the aneurysm. Beyond the risk of rupture and its complications, large and giant aneurysms can cause mass effect on the adjacent cranial nerves. A PcomA aneurysm especially can compress the oculomotor nerve against the tentorium and cause oculomotor palsy. Using endovascular treatment has shown a reduction of the mass effect on the cranial nerves after treatment when the pulsation of the aneurysm sac has decreased and the aneurysm thrombosed (Patel et al. 2014). The PcomA has multiple small arterial branches supplying the optic chiasm, the oculomotor nerve, the thalamus, the hypothalamus, and the internal capsule (Golshani et al. 2010; Patel et al. 2014). The treatment should therefore focus on maintaining the flow in the PcomA. The surgical treatment of large and giant aneurysms is associated with high morbidity and mortality, and endovascular treatment strategies are preferred for this kind of complex lesion (Ogilvy and Carter 2003). There are several endovascular treatment methods available to treat this kind of lesion (e.g., coil occlusion of the aneurysm with or without balloon or stent assistance). However, the aneurysm morphology was associated with an increased risk of coil protrusion which could have caused thrombosis of the PcomA. The remodeling technique is typically used in patients with wide neck aneurysms. In the case reported above, the aneurysm neck was narrow and the main concern was not potential coil protrusion into the internal carotid artery rather being able to preserve the PcomA while still occluding the aneurysm. The use of flow diverters has become an effective treatment strategy with rates of aneurysmal occlusion of approximately 69–94% at 6 months and 87–95% at 1 year. A risk of morbidity and mortality following flow diversion has been reported at between 0% and 19% (Lylyk et al. 2009). However, concerns regarding the patency of the covered side branches have been raised. In a study done by Daou et al. (Daou et al. 2017) in a group of 30 patients, the PcomA was patent in 23% and occluded in 53% of cases and the remaining 23% of patients experienced diminished flow at 6 months of treatment without any neurological symptom in any case. Approximately 10% of the PcomA aneurysms are associated with a fetal variant of the PcomA, and because a fetal PcomA represents the only supply of the posterior cerebral artery, extra care should be taken treating these types of aneurysms because of the risk of infarction and neurological symptoms (Fig. 4). In the literature, the reported experience of coil occlusion of aneurysms with a fetal variant of the PcomA had a low rate of permanent occlusion. This is because flow through the fetal PcomA and the aneurysm sac remains patent due to the high physiological demands on flow and the possibility of endoleak between the P1 and the PcomA. In cases of a fetal PcomA aneurysm, another technique should be considered (Tsang et al. 2015; Zanaty et al. 2016). The pCONUS2 is an intrasaccular device without flow disruption effect. It has a stent body structure with an articulated crown of six petals. The articulated crown allows the device to accommodate sharp angles between the parent vessel and the aneurysm. The petals are designed to create support for the coils and prevent protrusion into the parent vessel (Lylyk et al. 2018). After placing the crown inside the aneurysm, a second microcatheter crosses the device to coil the aneurysm, creating adequate support for the coil cast. Stent-assisted coil occlusion with a pCONUS 2 device seems to be a safe and feasible treatment option when – due to the anatomy of the patient – coil cast support is needed in order to prevent coil protrusion into the parent vessel or an efferent artery.

Fig. 4
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Stent-assisted coil occlusion of a left PcomA aneurysm in a 45-year-old female patient with a large caliber PcomA and no ipsilateral P1 segment, using a pCONUS2 bifurcation stent. The patient presented with chronic headache. CT/CTA showed a hypodense epidermoid cyst of the left middle cranial fossa with an adjacent unruptured PcomA aneurysm (a, b). Coronal (c) and axial (d) T1WI MRI confirmed the “white” (hyperintense on T1WI MRI) epidermoid. The patient asked for endovascular treatment of the aneurysm and received a loading dose of 500 mg ASA and 30 mg prasugrel on the day prior to the scheduled procedure. A VerifyNow test on the following day showed the dual platelet function inhibition (ARU 494, P2Y12 82% inhibition). DSA with injection of the left vertebral artery showed that the left P1 segment was missing (e). The injection of the left ICA confirmed the PcomA aneurysm with a largest fundus diameter of 8 mm and a neck width of 4 mm (f). Under road map the aneurysm was catheterized using a pNOVUS27 microcatheter (phenox). A pCONUS2 with 6 mm petal diameter was deployed inside the aneurysm. The petals were positioned at the neck level, with the articulation marker adjacent to the origin of the PcomA (arrow (g, h)). The pCONUS2 was electrolytically detached. An Excelsior SL-10 microcatheter (Stryker) was inserted into the aneurysm (arrow, (i)). A total of 12 Target coils (Stryker) were required to occlude the aneurysm (1× 360° standard 7/30, 1× 360° soft 5/10, 1× 360° soft 4/8, 5× helical nano 3/8, 2× helical nano 2.5/6, 1 × 2/6) (j, k). The procedure was well tolerated. The medication thereafter comprised 100 mg ASA PO daily for life and 10 mg prasugrel PO daily for 3 months. MRI including T2WI (l) and FLAIR images (m) 3 days later and prior discharge ruled out any ischemic or hemorrhagic complication. Follow-up DSA is pending

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Therapeutic Alternatives

  • Balloon Assisted Coiling

  • Flow Diverter

  • Microsurgical Clipping

  • Stent-assisted Coiling