Keywords dissectiong posterior cerebral artery aneurysm - flow diverter treatment - neck-crossing
technique - low-profile distal access catheter - pipeline flex embolization device
with shield technology
Introduction
In recent years, the adoption of flow diverters (FDs) for the treatment of cerebral
aneurysms has been remarkable.[1 ]
[2 ] Low-profile devices that can be navigated with a 17-catheter (microcatheter with
0.017” tip inner diameter) have become common, and good treatment results with small
distal arteries are well-known.[3 ]
[4 ] Meanwhile, only the Pipeline Flex Embolization Device with Shield Technology (PED-S;
Medtronic, Minneapolis, Minnesota, United States) and Flow Re-direction Endoluminal
Device (FRED; Terumo MicroVention, Aliso Viejo, California, United States), which
are compatible with 27-catheters (microcatheters with 0.027” tip inner diameter),
are available in our country. The indications for FDs have expanded to include the
internal carotid artery (ICA) and vertebral arteries (VAs) for the former, and, in
addition, the proximal parts of the anterior cerebral artery, middle cerebral artery,
and basilar artery (BA) for the latter. In this report, we present a case in which
the neck-crossing technique, using a novel distal access catheter (DAC),[5 ]
[6 ] proved successful in the placement of an FD for a challenging dissecting aneurysm
at the proximal segment of the right posterior cerebral artery. We discuss the advantages
and pitfalls, along with considerations, including a literature review.
Case Presentation
A 74-year-old female with a history of intermittent headaches for several years underwent
a head magnetic resonance imaging (MRI) examination, which revealed multiple unruptured
cerebral aneurysms. Her medical history included a hysterectomy for uterine disease
and antihypertensive medication due to hypertension. There were no notable findings
in her family history. She was referred to us to assess the indication for treating
the cerebral aneurysms and to address the necessary one.
Upon admission, the neurological examination revealed no focal neurological signs.
Neuroradiological imaging showed unruptured cerebral aneurysms in three locations
on magnetic resonance angiography, including the proximal right posterior cerebral
artery (PCA), the supraclinoid segment of the left ICA, and the distal right intracranial
VA distal to the posterior inferior cerebellar artery. MRI showed that a dome of the
proximal right PCA aneurysm compressed the right cerebral peduncle from the antero-medial
side ([Fig. 1A ]). Digital subtraction angiography (DSA) indicated that the last two aneurysms were
small or had a fusiform-shaped smooth configuration. As for the first one, just after
branching from the BA, the aneurysm was directed posteriorly and had a sharp bleb
at its tip ([Fig. 1B, D ]). The long diameter measured 9.8 mm, and the neck diameter was 8.7 mm, with the
PCA main trunk being involved in the aneurysm, suggesting a dissecting aneurysm ([Fig. 2A, B ]). The perforator of the P1 segment of the PCA was dominant on the left side, with
no apparent ones on the right side on DSA. No observable branches were originating
from the aneurysm wall. Based on these findings, endovascular treatment for the right
PCA aneurysm was deemed necessary, taking into account its shape and size. Initially,
stent-assisted coil embolization was considered. However, given the presence of a
fusiform aneurysm in the right VA and the strong tortuosity and stenosis of the left
VA to the BA, the introduction of multiple microcatheters for the jailing technique
was considered high-risk. Given the simplicity and curative potential of the treatment,
it was decided to proceed with FD treatment, utilizing catheter access through the
left VA. In our country, FD is not reimbursed by insurance for PCA aneurysms, so the
patient provided informed consent, including acknowledgment of the off-label use of
FD, and an understanding of the associated treatment risks at this specific location.
Fig. 1 (A ) Fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) showing
a dome of the proximal right posterior cerebral artery aneurysm compressing the right
cerebral peduncle from the anteromedial side. (B ) Anteroposterior (AP) view of a three-dimensional digital subtraction angiography
(3D DSA) of the left vertebral angiography (VAG) showing the right posterior cerebral
artery aneurysm. (C ) Translucent image of the AP view of the 3D DSA from the left VAG delineating the
dissecting nature of the aneurysm. (D ) Translucent image of the lateral view of the 3D DSA from the left VAG showing a
bleb at the upper posterior portion of the aneurysm.
Fig. 2 (A ) Measurement of the diameter and length of the left posterior cerebral artery (PCA)
and basilar artery (BA). (B ) Measurement of the aneurysm's width, height, and neck. (C ) Working angle view showing the expected course of the flow diverter from the BA
to the left PCA.
Endovascular Treatment
Dual antiplatelet treatment (aspirin 100 mg/day and prasugrel 3.75 mg/day) was initiated
14 days before the treatment. Platelet function evaluation by VerifyNow (Accumetrics,
San Diego, California, United States) performed 2 days before treatment showed ARU
394 and PRU 189, both of which were within optimal ranges. Under general anesthesia,
a 4Fr 10cm short sheath introducer was placed in the right superficial femoral artery,
and after confirming adequate puncture status by contrast, it was exchanged for a
7Fr 30cm long sheath introducer. Heparin (5,000 units) was systemically injected,
and 5 minutes later, an activated clotting time (ACT) of 367 seconds was confirmed.
Thereafter, heparin was additionally administered to maintain the ACT around 300 after
hourly ACT measurements. A 7Fr 90cm guiding catheter (Roadmaster; Nipro, Osaka, Japan)
was advanced to the level of the fourth cervical vertebra of the left VA. 3D-DSA was
performed, setting multiple working angles to access P1 ([Fig. 2C ]), the neck and the aneurysm body, and the distal PCA. Phenom Plus (outer diameter:
4.2-Fr. inner diameter: 1.13 mm; Medtronic) was selected as the DAC. After advancing
Phenom 27 (outer diameter: 2.8-Fr, 0.91 mm; Medtronic) using Synchro SELECT Standard
(Stryker, Kalamazoo, Minnesota, United States) inside Phenom Plus into BA via the
intracranial VA, when attempting to advance Phenom 27 to cross the lesion, difficulties
arose due to the sharp bending of the PCA just after the neck, as well as the branching
angle from the BA. Even after substituting the guidewire from Synchro SELECT Standard
to Traxess (Terumo MicroVention) and GT 0.012” double angle guidewire (Terumo MicroVention),
it remained unreachable. Therefore, the microcatheter was replaced with an Excelsior
SL-10 (Stryker), and the guidewire was switched to a Synchro SELECT Soft (Stryker)
with its tip manually shaped to a moderate degree. This allowed for successful distal
access, and the Excelsior SL-10 reached beyond the neck of the aneurysm to the P3
segment of the PCA. After changing the guidewire to a Chikai-14 300cm (Asahi Intecc,
Aichi, Japan), Phenom 27 was successfully crossed with a catheter exchange. A PED-S
3.25mm × 20mm (Medtronic) was selected as the FD and guided into the Phenom 27 ([Fig. 3A ]). However, at the angle just before reaching the neck from the P1 origin of BA,
the PED-S tip could not pass beyond it, even though the leading wire had passed through
([Fig. 3B ]). Attempts to force it caused a portion of Phenom 27, just proximal to its tip,
where the PED-S was advanced, to deflect into the dome. At this juncture, to secure
additional backup support, Phenom Plus was advanced cautiously, enabling it to follow
Phenom 27 smoothly without encountering any resistance ([Fig. 3C, D ]). Furthermore, as Phenom Plus was carefully advanced, it traversed from the BA to
the PCA, crossed the neck of the aneurysm, and reached the distal bend of the PCA,
beyond the aneurysmal neck ([Fig. 3E ]). Subsequently, PED-S was advanced and positioned inside Phenom 27, extending it
further beyond the intended landing zone ([Fig. 3F ]). While Phenom Plus was gradually retracted from the neck region toward the BA,
PED-S was opened and deployed, ensuring a secure landing ([Fig. 4 ]).
Fig. 3 X-ray fluoroscopic images during the treatment: (A ) Phenom 27 has reached the distal portion of the left posterior cerebral artery (PCA).
(B ) A Pipeline Embolic Device with Shield technology (PED-S) became stuck and could
not be advanced. (C ) The tip of the Phenom Plus (PP) is approaching the mid-basilar artery. (D ) The tip of the PP has reached the proximal neck of the aneurysm. (E ) The tip of the PP has passed beyond the distal neck of the aneurysm. (F ) The PED-S was advanced inside the Phenom 27 to the PCA, distal to the aneurysm.
Arrowhead: tip of the Phenom 27. Arrow: tip of the Pipeline Embolic Device with Shield
technology. Cross: tip of the Phenom Plus.
Fig. 4 X-ray fluoroscopic images during the treatment (continuation of [Fig. 3 ]): (A ) A Pipeline Embolic Device with Shield technology (PED-S) is positioned correctly
inside Phenom 27. (B ) The Phenom 27 is unsheathed, and the distal part of the PED-S is coming out of the
Phenom 27 while the tip of the Phenom Plus is moving proximally. (C ) The PED-S is gradually opening within the posterior cerebral artery (PCA), distal
to the aneurysm. (D ) The PED-S is successfully opened at the neck of the aneurysm. (E ) The proximal part of the PED-S is about to be deployed in the basilar artery. (F ) The PED-S has been fully deployed at the appropriate position. Arrowhead: tip of
the Phenom 27. Arrow: tip of the Pipeline Embolic Device with Shield technology. Cross:
tip of the Phenom Plus.
After deployment, there was significant flow stagnation within the aneurysm. High-resolution
cone-beam computed tomography confirmed the adequate adaptation of PED-S to the vessel
wall ([Fig. 5A ]), and angioplasty was not deemed necessary. Heparin reversal was not performed,
and the sheath introducer was removed using Perclose ProGlide (Abbott Vascular, Santa
Clara, California, United States). Postoperatively, there were no neurological abnormalities.
An MRI examination conducted on day 1 following the procedure showed no abnormalities,
including ischemic lesions ([Fig. 5B ]). The patient was discharged on day 4 postoperatively while maintaining dual antiplatelet
therapy. Currently, the patient is in the latency period for a follow-up DSA. A video
of the procedure is available ([Video 1 ]).
Fig. 5 (A ) High-resolution cone-beam computed tomography (CT) image showing the location of
the Pipeline Embolic Device with Shield technology. (B ) A fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) image
on day 1 showing no ischemic lesions. (C ) On the left, the Phenom 27 is inserted into the Phenom Plus, showing almost no ledge.
On the right, the Phenom Plus is inserted into a standard 5-French distal access catheter,
showing a significant ledge.
Video 1 The video file of the edited procedural footage.
Discussion
Dissecting aneurysms of the PCA is rare,[7 ] and there are no clear guidelines for treatment indications. In this case, although
it was unruptured and asymptomatic, the size and shape of the aneurysm led us to consider
treatment indications. The primary choice for curative treatment in this case was
endovascular therapy, given the location of the lesion.[8 ] Stent-assisted coil embolization is the first consideration in terms of endovascular
techniques. In this case, the aneurysm tip was directed posteriorly and indented partly
to the right cerebral peduncle, but not significantly, so stent-assisted embolization
may be an option. FD placement was also considered as an alternative.[9 ] Evidence supporting the use of FDs in peripheral artery aneurysms has been steadily
growing.[3 ]
[10 ] There is an increasing expectation for the use of low-profile FDs with smaller deployment
diameters in the treatment of peripheral artery aneurysms.[3 ]
[10 ]
Initially, stent-assisted coil embolization was considered in this case. However,
the presence of significant arterial sclerosis along the route from the left VA to
the BA made it challenging to achieve sufficient aneurysm occlusion using the jailing
technique with two microcatheters. It is important to note that in our country, low-profile
FDs for peripheral artery aneurysms have not yet been introduced, and reimbursement
for FDs in this location has not been established. While both PED-S and FRED were
considered options, we opted for the former due to factors such as the presence of
a coating[4 ]
[11 ]
[12 ]
[13 ] and its suitability for curved areas.[14 ] Therefore, Phenom 27 induction was necessary in this case. However, the placement
site had a bend in the right PCA beginning from the cerebral base artery, in addition
to the aneurysm's distal side, making it challenging to guide the microcatheter for
the FD.
As a result, we introduced a 17-catheter, instead of Phenom 27, and then induced the
latter by catheter exchange. At this point, the Phenom Plus, a low-profile DAC with
an outer diameter of 4.2 Fr (1.40 mm), provided sufficient backup support. Furthermore,
during the introduction of PED-S through Phenom 27, difficulties were encountered
as mentioned above. To overcome this, we carefully guided Phenom Plus along Phenom
27, successfully reaching the distal PCA by crossing the neck with Phenom Plus. With
only a 0.22 mm difference in diameter between the inner diameter of Phenom Plus (1.13 mm)
and the outer diameter of Phenom 27 (2.8 Fr, 0.91 mm), the ledge effect was minimal
([Fig. 5C ]). Therefore, this combination of a DAC and neck crossing was considered highly useful.
In recent years, the use of this DAC has increased in neuroendovascular treatment,
particularly through transradial access, owing to its low-profile design. Another
distinctive feature is the minimal ledge between this catheter and Phenom 27. Therefore,
the approach of using Phenom Plus as a low-profile DAC is considered to be more beneficial
in the treatment of peripheral artery aneurysms compared with conventional standard
DACs such as Sofia Select (Terumo MicroVention) and Navien (Medtronic). Specifically,
this technique may be applicable to aneurysms that are suitable for flow diversion
in arteries beyond the Circle of Willis, such as the anterior communicating artery,
middle cerebral artery, PCA, or even further distal arteries that are larger in diameter
than the outer diameter of the Phenom Plus, which is 4.2 Fr (1.40 mm).
To the best of our knowledge, this report represents the first documentation of a
FD treatment utilizing the neck-crossing technique for the distal cerebral aneurysm
using Phenom Plus, leveraging this specific characteristic.
As a limitation, it is important to note that this report represents a single case,
and this technique may not apply to all peripheral artery aneurysms. Caution is required
due to potential vascular risks, including vascular dissection caused by the DAC itself,
ischemia due to wedging into the parent vessel, and the possibility of pull-out perforating
arteries due to vascular stretching. Of course, long-term follow-up, including DSA,
is necessary to monitor the future course of this case.
Conclusion
We reported a case involving the placement of a FD for a dissecting aneurysm in the
right PCA. In this case, the neck-crossing technique with a low-profile DAC proved
to be valuable. This technique can serve as an alternative option for the treatment
of peripheral artery aneurysms with FDs, especially when achieving the introduction
of the FD or its delivery catheter proves to be challenging.
