CASE REPORT
Nagoya J. Med. Sci. 85. 157–166, 2023
doi:10.18999/nagjms.85.1.157

Single-lane clipping technique for a ruptured aneurysm of
A1 fenestration of the anterior cerebral artery:a case report and literature review
Yuki Kubota1, Yoshiki Hanaoka1, Tatsuro Aoyama2, Yu Fujii1,
Toshihiro Ogiwara1, Tatsuya Seguchi2
and Tetsuyoshi Horiuchi1
Department of Neurosurgery, Shinshu University School of Medicine, Matsumoto, Japan
2
Seguchi Neurosurgical Hospital, Iida, Japan

1

ABSTRACT
Fenestration of the A1 segment of the anterior cerebral artery is a rare vascular anomaly with a highrisk of saccular aneurysm at the proximal end of the A1 fenestration. These aneurysms have a high riskof rupture. However, conventional surgical clipping can be technically challenging due to the anatomical
characteristics. We report a case of A1 fenestration with a ruptured aneurysm wherein we successfully
achieved complete obliteration of the aneurysm with a new “single-lane” clipping technique. A 64-yearold woman presented with a ruptured saccular A1 aneurysm at the proximal end of an A1 fenestration,
resulting in subarachnoid hemorrhage. Microsurgical clipping was attempted; however, adequate exposureof the aneurysm could not be achieved. The recurrent artery of Heubner originated near the distal end of
the lateral limb of the A1 fenestration. The lateral limb of the A1 fenestration had no perforating arteries,
according to surgical examination. Thus, the aneurysm neck and lateral limb were concurrently obliteratedusing a nonfenestrated clip, preserving the medial limb of the A1 fenestration. The antegrade flow of therecurrent artery of Heubner was detected using the retrograde flow of the distal part of the lateral limbof the A1 fenestration during intraoperative indocyanine green video angiography. The postoperative course
was uneventful without any evidence of ischemic stroke. For A1 aneurysms arising from the proximal
end of the A1 fenestration, this technique may be a useful treatment option. Before using this technique,careful surgical exploration should be performed to assess the A1 perforating arteries.
Keywords: A1 aneurysm, anterior cerebral artery, medial lenticulostriate artery, nonfenestrated clip,
subarachnoid hemorrhage
Abbreviations:
ACoA: anterior communicating artery
MLA: medial lenticulostriate artery
RAH: recurrent artery of Heubner
This is an Open Access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
License. To view the details of this license, please visit (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Received: December 28, 2021; accepted: March 2, 2022
Corresponding Author: Yoshiki Hanaoka, MD, PhD
Department of Neurosurgery, Shinshu University School of Medicine,
3-1-1 Asahi, Matsumoto 390-8621, Japan
E-mail: hanaoka@shinshu-u.ac.jp
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INTRODUCTION
Fenestration of the A1 segment of the anterior cerebral artery is a rare but clinically importantvascular anomaly.1,2 It is frequently associated with saccular aneurysm at the proximal end of thefenestration. These aneurysms have a high risk of rupture, even when small.3-15 Thus, surgicalmanagement of A1 fenestration aneurysms is commonly required to achieve a favorable outcome.
However, surgical exposure of these aneurysms can be technically challenging due to the uniqueanatomical features at that location.
We have devised a new surgical clipping technique to concurrently obliterate the aneurysm
neck and one limb of the A1 fenestration using a nonfenestrated clip, preserving the otherlimb of the A1 fenestration. We call this the single-lane clipping technique. Here we present
a case of ruptured A1 fenestration aneurysm that was successfully treated with the single-laneclipping technique. We also review the literature on cases of A1 fenestration aneurysm treatedwith surgical clipping.

CASE REPORTA 64-year-old woman with no medical history presented to our hospital with a sudden
onset headache. On admission, her score on the Glasgow Coma Scale was 14 (E3V5M6). No
neurological deficits were present. A computed tomography scan revealed a diffuse subarachnoid
hemorrhage (Figure 1A). An angiography found the following: 1) An A1 fenestration in the distal
part of the left A1 segment; 2) The recurrent artery of Heubner (RAH) originating from the distal
part of the lateral limb of the A1 fenestration; 3) A saccular A1 aneurysm (2.9 mm) arising fromthe proximal end of the A1 fenestration; and 4) A saccular anterior communicating artery (ACoA)
aneurysm (2.4 mm) (Figures 1B, 1C). The A1 fenestration aneurysm projected superomedially,
whereas the ACoA aneurysm projected anteriorly (Figures 1B, 1C). Due to the small size ofthe aneurysms, emergency clipping surgery was scheduled. The patient underwent microsurgicalclipping via a left pterional approach. Figure 2A shows a preoperative three-dimensional rotational
angiography corresponding to the surgical field. Surgical exploration demonstrated that the ACoA
aneurysm was unruptured. A 4-mm bayonet clip (Yasargil Aneurysm Clip System, FT727T;
Aesculap, Tuttlingen, Germany) was successfully applied to the neck of the ACoA aneurysm.
Subsequently, surgical clipping of the A1 fenestration aneurysm was attempted. The lateral limbof the A1 fenestration, the RAH, and the medial limb of the A1 fenestration were identified(Figure 2B). Careful intraoperative inspection revealed that there were no medial lenticulostriate
arteries (MLAs) arising from the lateral limb of the A1 fenestration (Figure 2B). A dense fibrin
cap covered the A1 fenestration aneurysm, suggesting a rupture. The aneurysm neck on the sideof the medial limb of the A1 fenestration was exposed but the aneurysm neck on the side ofthe lateral limb of the A1 fenestration could not be adequately visualized as it was behind thelateral limb of the A1 fenestration (Figure 2B). Thus, sufficient exposure of the A1 aneurysm
was technically challenging. A 7-mm nonfenestrated straight clip (Yasargil Aneurysm Clip
System, FT720T; Aesculap) was applied to both the aneurysm neck and the proximal part ofthe lateral limb of the A1 fenestration while preserving the medial limb of the A1 fenestration.
This changed the two-lane vessel to a single-lane vessel (Figure 2C). The following was revealed
by intraoperative indocyanine green video angiography: 1) The A1 fenestration aneurysm had no
indocyanine green filling; 2) The antegrade flow in the anterior cerebral artery was preserved
via the medial limb of the A1 fenestration; and 3) The antegrade RAH flow was maintained
via the retrograde flow of the distal part of the lateral limb of the A1 fenestration (Figure 2D).
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Single-lane clipping technique

Additional clipping using a 5-mm nonfenestrated straight clip (Yasargil Clip System, FT710T;
Aesculap) was performed (Figure 2E).
The postoperative course was uneventful. Postoperative angiography showed complete obliteration of both the ACoA and A1 aneurysms as well as patency of the medial limb of the A1
fenestration and RAH (Figure 3A). Postoperative magnetic resonance imaging found no evidenceof ischemic stroke (Figure 3B). On postoperative day 48, the patient was discharged with noneurological deficits. The patient is clinically stable without disability three months after thesurgery.

Fig. 1Preoperative computed tomography (CT) (A) and three-dimensional rotational angiography (3D-RA)of the left internal carotid artery injection (B, C)
Fig. 1A: Preoperative CT showing diffuse subarachnoid hemorrhage.
Fig. 1B: Antero-posterior view of preoperative 3D-RA showing a fenestration in the distal part of the A1 segmentof the anterior cerebral artery (ACA). A saccular aneurysm can be seen arising from the proximal endof the A1 fenestration (single asterisk) and the anterior communicating artery aneurysm (double asterisk).
The recurrent artery of Heubner (arrowheads) originates from the lateral limb of the A1 fenestration.
Fig. 1C: Cranial view (left) and caudal view (right) of a preoperative 3D-RA depicting the ACA. The A1
fenestration aneurysm projects superomedially and is located in a narrow space enclosed with the A1
fenestration.

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Fig. 2Preoperative three-dimensional rotational angiography (3D-RA) (A) andintraoperative video images (B, C, D, E)
Fig. 2A: Preoperative 3D-RA corresponding to the surgical field (caudal view). The medial limb of the A1
fenestration, the lateral limb of the A1 fenestration, the recurrent artery of Heubner (arrowheads), theanterior communicating artery (ACoA) aneurysm (double asterisk) were found. Note that only the neckof the A1 fenestration aneurysm (single asterisk) is visible.
Fig. 2B: A microsurgical view through the left pterional approach after clipping of the ACoA aneurysm. The
neck of the A1 fenestration aneurysm (single asterisk) on the side of the lateral limb could not beadequately visualized as the neck was behind the lateral limb. Surgical exploration revealed that thelateral limb had no A1 perforating arteries except for the recurrent artery of Heubner (arrowheads).
Fig. 2C: The aneurysm neck and the lateral limb were concurrently obliterated with a nonfenestrated straightclip, preserving the medial limb.
Fig. 2D: Intraoperative indocyanine green angiography with GLOW800 (Leica Microsystems, Wetzlar, Germany)
showed obliteration of the A1 fenestration aneurysm and patency of the A2 segment and recurrent
artery of Heubner.
Fig. 2E: A second clip was placed parallel to the first to reinforce the closure.

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Single-lane clipping techniqueFig. 3 Postoperative three-dimensional rotational angiography (3D-RA) (A) anddiffusion-weighted imaging (DWI) (B)
Fig. 3A: The anterior communicating artery aneurysm and the A1 fenestration aneurysm were completely obliterated, preserving the medial limb of the A1 fenestration and recurrent artery of Heubner (arrowheads).
Fig. 3B: A postoperative DWI showed no evidence of ischemic stroke.

DISCUSSION
A review of the literature identified 19 cases of A1 fenestration aneurysms treated with surgicalclipping. These are shown in Table 1.3-18 We have included our own for comparison. The cases
comprised 11 males and 9 females with a mean age of 55.7 years (range: 33–78 years). All 20
aneurysms were saccular, and 15 (75.0%) were ruptured. In 18 cases (90.0%), the aneurysm was
located at the proximal end of the A1 fenestration. Of the remaining two, one (5.0%) aneurism
was located on the medial limb of the A1 fenestration and one (5.0%) on the lateral limb of the
A1 fenestration. Of the 20 cases, aneurysm projections were described in 18 cases: superomedial
projections in 13 cases (72.2%), inferior projections in two cases (11.1%), medial projections
in two cases (11.1%), and an inferomedial projection in one case (5.6%). Aneurysm size wasrecorded in 11 of the 20 cases. The mean aneurysm size was 5.4 mm (range: 2.9–10.0 mm).

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Ruptured

41/M

38/M

162

49/M

50/F

Aktüre et al13
(2012)

52/F

Wanibuchi et al16
(2001)

Leyon et al12(2008)

68/M

Talor et al10(2000)

78/F

65/F

Ogasawara et al9(1988)

Ihara et al11(2003)

50/F

Kachhara et al8(1998)Friedlander et al7(1996)

33/M

Ruptured

56/M

Minakawa et al5(1985)

Wakabayashi et al6(1985)

Ruptured

50/F

Handa et al4(1984)

Ruptured

Ruptured

Ruptured

Unruptured

Ruptured

Ruptured

Ruptured

Ruptured

Ruptured

Ruptured

41/M

Korosue et al3(1983)

Type

Age(years)/sex

Authors

NA

Proximal end of right
A1 fenestration

Proximal end of right
A1 fenestration

Proximal end of right
A1 fenestration

Lateral trunk of left
A1 fenestration

Proximal end of left
A1 fenestration

Medial trunk of left
A1 fenestration

Proximal end of left
A1 fenestration

Proximal end of right
A1 fenestration

Superomedial

Superomedial

Superomedial

Superomedial

Inferior

Inferior

Superomedial

Superomedial

NA

Proximal end of right
A1 fenestration

Proximal end of right
A1 fenestration

Superomedial

Superomedial

Superomedial

Projection

Proximal end of left
A1 fenestration

Proximal end of right
A1 fenestration

Proximal end of right
A1 fenestration

Location

NA

4.0

NA

4.3

5.0

NA

NA

NA

6.5

5.0

NA

NA

NA

Size (mm)Simple neckclipping

Contralateral A1
fenestration andazygos ACA

Contralateral A1
fenestration

Simple neckclipping

Simple neckclipping

Simple neckclipping

Contralateral A1
hypoplasia andazygos ACA
None

Simple neckclipping

Simple neckclipping

Ipsilateral M1
hypoplasia
None

NA

Simple neckclipping withwrapping

None

Non-fenestrated
clip

Non-fenestrated
clip

Non-fenestrated
clip

NA

NA

NA

NA

NA

NA

NA

NA

NA

Clip shape

Simple neckclipping

Contralateral A1
aplasiaNA

NA

Simple neckclipping

Simple neckclipping

Simple neckclipping

Surgicalprocedure

None

None

Extracranial VA
fenestration

NA

None

Associatedvascularanomalies

Cases of A1 fenestration aneurysms treated with surgical clipping

A1 fenestration aneurysm

Table 1

None

None

None

None

None

NA

None

None

NA

NA

NA

NA

None

GR

GR

GR

GR

GR

VS

GR

GR

MD

D

NA

GR

D

Outcome
Surgical(GOS) atcomplications
discharge

Yuki Kubota et al

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163

Unruptured

63/M

Ruptured

Unruptured

62/M

64/F

Ruptured

49/F

Unruptured

Unruptured

72/M

73/M

Ruptured

59/F

ACA: anterior cerebral artery
ACoA: anterior communicating artery
D: death
F: female
GOS: Glasgow Outcome Scale
GR: good recovery
M: male
MCA: middle cerebral artery
MD: moderate disability
NA: not available
VS: vegetative state
VA: vertebral artery

Current case

Mamadaliev et al18
(2019)

Gill et al15
(2019)

Iwabuchi et al17(2018)

Kwon et al14
(2013)

Superomedial

MedialMedialSuperomedial

Proximal end of right
A1 fenestration
Proximal end of right
A1 fenestration
Proximal end of right
A1 fenestration
Proximal end of left
A1 fenestration

Superomedial

Superomedial

Proximal end of left
A1 fenestration

Proximal end of left
A1 fenestration

Inferomedial

Proximal end of right
A1 fenestration

2.9

NA

4.2

8.0

7.0

10.0

2.9

None

None

Non-fenestrated
clip

Simple neckclipping

Clipping for
Non-fenestrated
aneurysm neck
ACoA aneurysm
clip
and lateral limbof A1 fenestration

None

None

Fenestrated clip

Simple neckclipping

None

Fenestrated clip

None

None

None

Clipping ofaneurysm neckFenestrated clip
and lateral limbof A1 fenestration
Clipping ofaneurysm neckFenestrated clip
and lateral limbof A1 fenestration

None

Non-fenestrated
clip

Simple neckclipping

Simple neckclipping

Contralateral A1
hypoplasia andazygos ACANANA

MCA aneurysm,
azygos ACA, andcontralateral A1
aplasia

GR

GR

GR

GR

GR

GR

GR

Single-lane clipping technique

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Yuki Kubota et al

Simple neck clipping for A1 fenestration aneurysms can be technically problematic. Most of
the A1 fenestration aneurysms in our literature review were ruptured at presentation and projectedsuperiorly. Therefore, frontal lobe retraction should be minimized to prevent premature rupture ofaneurysms.12 Given the surgical trajectory, aneurysm projection, and narrow operative space, it canbe challenging to entirely expose aneurysms arising from the proximal end of an A1 fenestration.
Particular attention must be paid to the preservation of the A1 perforating arteries, including
the MLAs and RAH. The MLAs supply the septum pellucidum, the medial part of the anterior
commissure and pallidum, the pillars of the fornix, the paraolfactory area, the anterior limb of
the internal capsule, the anterior-inferior part of the striatum, and the anterior hypothalamus. The
RAH perfuses the anterior-inferior striatum, the anterior limb of the internal capsule, the olfactory
region, the anterior hypothalamus (overlapping the MLAs), the frontobasal cortex, and subcorticalwhite matter.19 Therefore, serious neurological deficits can result from damage to these arteries.
Small aneurysms are a well-known risk factor for aneurysm perforation during cerebral
aneurysm coil embolization.20 Both the ACoA and A1 fenestration aneurysms were small inthis patient. Thus, we employed clipping surgery for the aneurysms. The clip head used for the
ACoA aneurysm did not appear to interfere with the clipping of the A1 fenestration aneurysm
because the ACoA aneurysm was located in the deep operative field compared to the A1
fenestration aneurysm. Hence, initially, the ACoA aneurysm was clipped, followed by the A1
fenestration aneurysm. Simple neck clipping was considered technically difficult and potentiallyhazardous because surgical exposure of the A1 fenestration aneurysm could not be adequately
achieved. A previous report found that the vital MLAs commonly arise from the medial limb of
an A1 fenestration.12 In our case, no MLAs arose from the lateral limb of the A1 fenestration.
Therefore, the aneurysm neck and the proximal part of the lateral limb of the A1 fenestration
were concurrently obliterated with a nonfenestrated clip, preserving the medial limb of the A1
fenestration. Additional clipping was performed to reinforce the closure.
This technique enables neurosurgeons to achieve aneurysm neck clipping without total exposureof an A1 fenestration aneurysm. Neck clipping of A1 fenestration aneurysms using fenestrated
clips has been reported.16 However, neurosurgeons must pay meticulous attention to both the tip
and heel of the fenestrated clip blade to place the clip correctly through the limited surgicalfield.16 The single-lane clipping technique is simple as neurosurgeons need only ensure that the
tip of the nonfenestrated clip blade does not clip the medial limb of the A1 fenestration. This
technique can be a useful treatment option for A1 aneurysms arising from the proximal end of
A1 fenestrations, especially for ruptured and superiorly projecting aneurysms, which account formost A1 fenestration aneurysms.
Perforator territory infarction can occur as a result of delayed thrombosis at the occluded
parent artery’s blind end.21,22 The MLAs mostly originate from the proximal part of the A1
segment.19 The A1 fenestration is commonly located in the distal part of the A1 segment.23
Therefore, our method may be applied in many cases of A1 fenestration aneurysms. However,before applying this method, surgical exploration is essential to evaluate whether A1 perforatingarteries arise from the target limb of the A1 fenestration.

AUTHOR CONTRIBUTIONYK and YH contributed equally as first authors to this work.

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Single-lane clipping technique

CONFLICT OF INTEREST
The authors have no conflicts of interest to disclose.

ETHICS APPROVALThis study was performed in accordance with the ethical standards of the 1964 Declarationof Helsinki and its later amendments.

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