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Surgical Neurology 70 (2008) 135 – 152
www.surgicalneurology-online.com
Aneurysm-Rainbow Team/Helsinki
Microneurosurgical management of aneurysms at
A3 segment of anterior cerebral artery
Martin Lehecka, MDa , Reza Dashti, MDa , Juha Hernesniemi, MD, PhDa,⁎,
Mika Niemelä, MD, PhDa , Timo Koivisto, MD, PhDb , Antti Ronkainen, MD, PhDb ,
Jaakko Rinne, MD, PhDb , Juha Jääskeläinen, MD, PhDb
a
Department of Neurosurgery, Helsinki University Central Hospital, 00260 Helsinki, Finland
b
Department of Neurosurgery, Kuopio University Hospital, 70211 Kuopio, Finland
Received 17 December 2007; accepted 1 March 2008
Abstract
Background: Aneurysms originating from the A3 segment of anterior cerebral artery (A3A) form
about 5% of all IAs. They are the most common among distal anterior cerebral artery aneurysms.
There are relatively few reports on management of A3As. In this article, we review the practical
anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and
clipping of A3As.
Methods: This review, and the whole series on IAs, is mainly based on the personal
microneurosurgical experience of the senior author (JH) in 2 Finnish centers (Helsinki and Kuopio),
which serve, without patient selection, the catchment area in Southern and Eastern Finland.
Results: These 2 centers have treated more than 10000 patients with IAs since 1951. In the Kuopio
Cerebral Aneurysm Database of 3005 patients and 4253 IAs, there were 163 patients carrying 174
A3As, forming 5% of all patients with IAs, 4% of all IAs, and 15% of all ACA aneurysms. Ninetyseven (60%) patients presented with ruptured A3As with ICH in 27 (28%) and IVH in 26 (27%).
Ninety-four (58%) patients had multiple aneurysms.
Conclusions: Aneurysms of A3 segment of ACA are often small, even when ruptured, with
relatively wide base, and they are frequently associated with ICHs of IVHs. Our data suggest that
A3As rupture at smaller size than IAs in general. The challenge is to select appropriate approach, to
locate the aneurysm deep inside the interhemispheric fissure, and to clip the neck adequately without
obstructing branching arteries at the base. Unruptured A3As also need microneurosurgical clipping
even when they are small.
© 2008 Elsevier Inc. All rights reserved.
Keywords:
Aneurysm; Anterior cerebral artery; Clipping; Distal; Callosomarginal artery; Microanatomy; Microsurgical technique; Pericallosal
artery; Subarachnoid hemorrhage
Abbreviations: A1, proximal segment of anterior cerebral artery; A1A, aneurysm of the A1 segment; A2, A2 segment of anterior cerebral artery; A2A,
aneurysm of A3 segment of anterior cerebral artery; ACA, anterior cerebral artery; ACoA, anterior communicating artery; ACoAA, anterior communicating
artery aneurysm; AdistA, aneurysm distal to A3 segment of anterior cerebral artery; AIFA, anterior internal frontal artery; CMA, callosomarginal artery; CSF,
cerebrospinal fluid; CTA, computed tomographic angiography; DACA, distal anterior cerebral artery; DSA, digital subtraction angiography; IA, intracranial
aneurysm; ICA, internal carotid artery; ICG, indocyanine green; ICH, intracerebral hematoma; ICP, intracerebral pressure; IVH, intraventricular hemorrhage;
MCA, middle cerebral artery; MIFA, middle internal frontal artery; MRI, magnetic resonance imaging; PIFA, posterior internal frontal artery; SAH,
subarachnoid hemorrhage; STA, superficial temporal artery.
⁎ Corresponding author. Tel.: +358 50 427 0220; fax: +358 9 471 87560.
E-mail address: [email protected] (J. Hernesniemi).
0090-3019/$ – see front matter © 2008 Elsevier Inc. All rights reserved.
doi:10.1016/j.surneu.2008.03.019
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M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
1. Introduction
Aneurysms of the ACA can be classified into 5 different
groups as follows: A1As or proximal anterior cerebral artery
aneurysms; ACoAAs; A2As or proximal pericallosal aneurysms; A3As or classical pericallosal aneurysms; and AdistAs
or distal pericallosal artery aneurysms (Table 1, Fig. 1) [5].
The last 3 groups, also called DACA aneurysms, are further
divided into 7 subgroups according to microneurosurgical
criteria (Fig. 2).
1.1. A3 segment aneurysms
The A3As are located at the A3 segment of the ACA at
the genu of corpus callosum, often at the origin of the CMA.
They have also been called pericallosal artery–callosomarginal artery junction aneurysms or loco classico pericallosal
artery aneurysms.
The A3As are the most common of the DACA aneurysms
(see previously), forming 2% to 7% of all intracranial
aneurysms, with relatively small series on their management
[9,11,21,23,35,36,42,47,55,66,71,85,89,90]. The A3As are
small and often associated with ICH when ruptured
[21,27,36,40,56,66,68,71]. The A3As are difficult to reach
as they lie deep in the interhemispheric fissure closely
attached to the surrounding brain tissue. Their location deep
inside the narrow interhemispheric fissure, wide base,
frequent involvement with vascular anomalies of the region,
as well as branches originating from their base make their
intraoperative identification and microneurosurgical clipping
challenging [3,4,9,21,23,35,36,40,42,45,47,51,56,66,71,82,
85,88,90].
1.2. Purpose of review
Fig. 1. Illustration demonstrating segments and branches of ACA and
location of A3As.
Eastern Finland. These 2 centers have treated more than
10000 aneurysm patients since 1951.
The data presented in our series of articles represent 3005
consecutive patients harboring 4253 IAs from the Kuopio
Cerebral Aneurysm Database (1977-2005). The aim is to
present a consecutive, nonselected, population-based series
of IAs. This database is not reflective of the personal series of
the senior author (JH) alone.
This review, and the whole series on intracranial
aneurysms, is intended for neurosurgeons who are subspecializing in neurovascular surgery. The purpose is to
review the practical anatomy, preoperative planning, and
avoidance of complications in the microsurgical dissection
and clipping of A3As.
1.3. Authors
The microneurosurgical technique in this review is
mainly based on the personal experience of the senior author
(JH) in 2 Finnish centers (Helsinki and Kuopio), which
serve, without selection, the catchment area in Southern and
Table 1
Five categories of ACA aneurysms (see Fig. 1)
Category Location
A1A
ACoAA
A2A
A3A
AdistA
A1 segment, between ICA bifurcation and ACoA
Anterior communicating artery
A2 segment and its frontobasal branches, between ACoA and
genu of corpus callosum
A3 segment, curving around genu of corpus callosum
A4 and A5 segments or distal cortical branches such as CMA
Fig. 2. Microsurgical division of distal anterior cerebral artery aneurysms
with emphasis on A3As.
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
Table 2
Patients with ACA aneurysms in a consecutive and population-based series
of 3005 patients with 4253 IAs from 1977 to 2005 in the Kuopio Cerebral
Aneurysm Database
Whole series
Patients with primary SAH
Patients without primary SAH
ACA aneurysms
A1As
ACoAAs
A2As
A3As
AdistAs
Ruptured ACA aneurysms
A1As
ACoAAs
A2As
A3As
AdistAs
Fusiform ACA aneurysms
Fusiform A1A
Fusiform ACoAA
Fusiform A2A
Fusiform A3A
Fusiform AdistA
No. of patients
No. of aneurysms
3005
2365
640
1145
23 (2%)
898 (78%)
35 (3%)
163 (14%)
26 (2%)
855
12 (1%)
715 (84%)
21 (2%)
97 (11%)
10 (1%)
6
2
3
1
0
0
4253
3325
928
1179
23 (2%)
921 (78%)
35 (3%)
174 (15%)
26 (2%)
855
12 (1%)
715 (84%)
21 (2%)
97 (11%)
10 (1%)
6
2
3
1
0
0
1.4. Occurrence of A3As
The incidence of A3As is 2% to 7% of all IAs or 69% to
82% of all DACA aneurysms [9,21,23,35,36,42,47,55,66,
71,85,89,90]. Tables 2 to 5 present the clinical data on the
163 A3A patients in the consecutive and population-based
series of 3005 patients with 4253 IAs from 1977 to 2005 in
the Kuopio Cerebral Aneurysm Database. Of the 3005
patients, 1145 (38%) had 1179 ACA aneurysms (Table 2).
There were 163 patients with 174 A3As, 4% of all the 4253
IAs, 15% of all the 1179 ACA aneurysms, and 74% of all the
Table 3
Characteristics of 174 A3As
Ruptured
No. of aneurysms
Median aneurysm
size (mm)
Aneurysm size
Small (b7 mm)
Medium
(7-14mm)
Large (15-24mm)
Giant (≥25mm)
Aneurysm side
Right
Left
ICH
Temporal
Frontal
Parietal
IVH
Preoperative
hydrocephalus
137
Table 4
Intracerebral hematoma, IVH, and acute hydrocephalus associated with
aneurysm rupture on different ACA segments
A1As
ACoAAs
A2As
A3As
AdistAs
Ruptured
12
715
21
97
10
aneurysms
ICH only
3 (25%) 33 (5%)
6 (29%) 13 (13%) 2 (20%)
ICH with IVH
0 (0%)
74 (10%) 5 (24%) 14 (14%) 2 (20%)
component
IVH only
2 (17%) 137 (19%) 2 (10%) 12 (12%) 0 (0%)
Preoperative
5 (42%) 317 (44%) 7 (33%) 32 (33%) 1 (10%)
hydrocephalus
235 DACA aneurysms. Most of the A3As were located
anterior to the genu of the corpus callosum at the origin of the
CMA. The left side (n = 101, 58%) slightly dominated over
the right side (n = 73, 42%). There were no fusiform A3As.
Giant A3As are extremely rare [11-13,18,21,36,39,46,49,53,
54,67,71,74,77], only one in our series (Table 3).
1.5. Ruptured and unruptured A3As
In our series, 855 (73%) of the 1179 ACA aneurysms
presented with SAH, of which 97 (11%) were A3As
(Table 2). Of our 174 A3As, 97 (58%) were ruptured and 77
(42%) unruptured (Table 3). Their size distribution is presented
in Table 3. Of the 97 ruptured A3As, 59 (61%) were smaller
than 7 mm, suggesting that even small unruptured A3As would
require occlusive therapy.
1.6. Intracerebral hematoma and IVH
Ruptured DACA aneurysms bleed frequently into the
adjacent brain [19,36,40,68,71]. Of the 97 patients with
ruptured A3A, ICH was present in 27 (28%) and IVH in 26
(27%) (Table 3, Fig. 3A). Bleeding into the frontal lobe often
extends into the ventricle (Table 4).
1.7. Associated aneurysms
Unruptured
Total
97
77
174
6 (range, 2-40) 3 (range, 1-11)
6 (range, 1-40)
59 (61%)
33 (34%)
61 (79%)
16 (21%)
4 (4%)
1 (1%)
0 (0%)
0 (0%)
37 (38%)
60 (62%)
27 (28%)
1
24
2
26 (27%)
32 (33%)
36 (47%)
41 (53%)
-
Data are given in number of aneurysms.
120 (69%)
49 (28%)
4 (2%)
1 (0.6%)
73 (42%)
101 (58%)
-
The DACA aneurysms are often associated with other
aneurysms [9,21,36,47,56,88,90]. In our series, 94 (58%) of
the 163 patients had at least one associated aneurysm (Table 5),
most frequently on the MCA. Multiple A3As occurred in 24
(15%) patients, in 17 on the opposite A3, and in 4 on the same
A3, and 3 had associated A3As on the both A3s (Table 5).
Table 5
Patients with an A3A and possible associated aneurysms
Ruptured Unruptured Total
Patients with A3A
Patients with single aneurysm
Patients with multiple aneurysms
Associated A3As
Same pericallosal artery
Opposite pericallosal artery
Both pericallosal arteries
Associated aneurysms at other sites
Data are given in number of patients.
97
62 (64%)
35 (36%)
10
2
6
2
25
66
7 (11%)
59 (89%)
14
2
11
1
45
163
69 (42%)
94 (58%)
24
4
17
3
70
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2. Microsurgical anatomical considerations of A3As
2.3. A3 segment and its braches
2.1. Anterior cerebral artery
The A3 segment starts at the junction of the rostrum and
the genu of the corpus callosum, curves around the genu, and
terminates at the start of the horizontal part of the ACA [14]
(Fig. 2). All A3 to A5 segments coursed in the callosal sulcus
in 60%, at least one segment was found in the cingulate
sulcus in 33% and in 7%, the A3 to A5 segments, were
located in the cingulate sulcus, not involving the corpus
callosum at all [78]. The A3 segment gives origin to several
cortical branches as follows: the AIFA; MIFA; the PIFA; and
most important, the CMA [51]. High variation in the origin
and size of these branches makes it impossible to define a
The microneurosurgical anatomy of ACA and its
branches has been well described [2,3,16,24,29,41,51,52,
78,88]. The ACA, the smaller of the 2 terminal branches of
the ICA, arises at the medial end of the sylvian fissure
lateral to the optic chiasm. It traverses the optic chiasm or
the optic nerve, ascends in front of the lamina terminalis in
the lamina terminalis cistern. Before entering the interhemispheric fissure, it is connected to the opposite ACA via the
ACoA (Fig. 1). In the interhemispheric fissure, the left and
right ACA trunks run parallel along the corpus callosum, in
the pericallosal cistern. Both trunks give origin to several
cortical, subcortical, and callosal branches, some of which
may cross over to the opposite side. Cortical branches of
the ACA supply the anterior two thirds of the medial
aspects of the cerebral hemisphere as well as the superior
portions of the superior frontal, precentral, and postcentral
gyri [51].
The ACA is divided into 5 segments, A1 to A5, according
to Fischer [14] (Table 1, Fig. 1). The A1 segment is located
between the ICA bifurcation and the ACoA. The A2 segment
extends from the ACoA to the region between the rostrum
and the genu of the corpus callosum. The A3 segment curves
around the genu of corpus callosum and ends at the rostral
part of the body of the corpus callosum. The A4 and A5
segments follow the superior surface of the corpus callosum
with a virtual plane of division at the level of the coronary
suture. Traditionally, the ACA has been divided into a
proximal part (A1) and a distal part (A2-A5), the latter also
called the pericallosal artery [16,24,29,51,80,89].
2.2. A2 segment
The A2 segment originates at the junction of the A1 and
the ACoA (Fig. 1). It ascends in the lamina terminalis
cistern, in front of the lamina terminalis, enters the
interhemispheric fissure and the callosal cistern with a
course toward the genu of the corpus callosum. The A2
terminates at the junction of the rostrum and the genu of the
corpus callosum where the A3 segment starts [51,87]. Inside
the interhemispheric fissure, A2s were side by side in 18%,
the left A2 anteriorly in 48%, and the right A2 anteriorly in
34% [52]. The free margin of the anterior falx is well above
the corpus callosum. The A2 segment is entirely below the
free margin that allows free shift and crossover of its
branches across the midline [51]. This means that both A2
segments can be reached from a unilateral approach [21,88].
The rostrum and the genu of corpus callosum are mainly
supplied by the subcallosal artery that usually originates
from the ACoA, courses posteriorly toward the region of
lamina terminalis, and ascends along the rostrum in the
midline [78]. In 25% of cases, this artery extends beyond the
genu of corpus callosum and continues along the body of
corpus callosum [78].
Fig. 3. A: Intracerebral hematoma with IVH component related to ruptured
anterior A3A. B: Dislocation of the pericallosal arteries (arrow) because of
the ICH.
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
139
standard vascular pattern for the A3s [29,51,80]. Some of the
cortical branches may have a common trunk of origin, may
arise from different segments, or may be totally absent
[29,51,80]. The 3 internal frontal arteries (see previously)
supply the medial and lateral surfaces of the superior frontal
gyrus as far posteriorly as the paracentral lobule [61]. In
addition to the cortical branches, there are also thin arteries
originating from the A3 to A5 segments that directly supply
the superficial surface of the corpus callosum, called callosal
and cingulocallosal arteries [78].
2.4. Callosomarginal artery
The CMA is the major branch of the distal ACA with
diameter of 1.8 to 1.9 mm, as thick as the ACA at the same
level [51,80]. Like other cortical branches of the ACA, the
CMA cannot be defined by its branches because the usual
branches of that region can arise directly from the ACA
trunk as well. The CMA has been defined as the artery that
courses in or near the cingulate sulcus and gives rise to 2 or
more major cortical branches [43]. The CMA is totally
absent in 9% to 18% [24,29,51,80]. It originated most
frequently (73%) at the A3, but origins from the A2 or the
A4 were also observed [51]. After its origin, the CMA
courses in or near the cingulate sulcus and often gives rise to
several cortical branches. According to the course, 3 types
of hemispheres have been described: (1) no CMA; (2)
atypical CMA, lacking long course in the cingulate sulcus
and oriented directly toward the cortex; and (3) typical
CMA, running parallel to the pericallosal artery in the
cingulate sulcus for a relatively long distance [80]. The
origin of the CMA is the most frequent site for the DACA
aneurysms [9,21,36,47,56,71].
Fig. 5. Superior sagittal sinus (SSS) and its relation to venous lacuna,
meningeal sinus, and bridging veins.
2.5. Anatomical anomalies of ACA
The important anomalies involving the ACA are the
azygos ACA; bihemispheric ACA; triplication of ACA; and
crossover branches of the ACA [3,16,34,38,51,87]. The
azygos ACA is a single trunk distal to the A1 segments, so it
is the supplier of the both hemispheres. In the bihemispheric
ACA, one A2 is hypoplastic and the larger A2 gives origin to
most cortical branches (Fig. 4). In case of the triplication of
ACA, the middle A2, also called the hemispheric type of the
medial callosal artery [78], is prominent and supplies the
corpus callosum. Crossover branches, found in 26% to 64%
of hemispheres, are sent from distal ACA to the contralateral
hemisphere where they supply a small medial area [51,69].
Severing of crossover branches may cause injury in the
contralateral side to the approach.
Association between anomalies of the ACA and DACA
aneurysms was seen in large angiographic series [22].
Clinical observations on the association are mainly based on
case reports [74]. In clinical series, anomalies of the ACA
occurred in 7% to 35% of the patients with DACA
aneurysms, more often than in the anatomical studies
[4,23,35,71,88]. In anatomical studies, the azygos ACA
was seen in 0.2% to 4%, the bihemispheric ACA in 0.2% to
12%, and the triplication of ACA in 3% to 13% of patients
[3,16,29,38,51,69,79,80,87].
2.6. Interhemispheric fissure
Fig. 4. Bihemispheric ACA with A3A (arrow), note the hypoplastic A2 on
the left (small arrows).
The A3As are located in the midline, inside the
interhemispheric fissure, where the cerebral hemispheres
are partially separated by the falx. The depth of falx varies,
but its free margin is well above the corpus callosum.
Importantly, the A2 and A3 segments are below the free
margin that allows free shift and crossover of their branches
across the midline [51]. On the other hand, only the most
anterior portion of the CMA is below the free margin. The
cingulate gyri may be so adherent to each other that during
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M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
the surgical exposure they may be mistaken for the corpus
callosum [88]. The interhemispheric fissure is so narrow that
only limited amount of CSF can be removed.
2.7. Venous structures
The veins draining the lateral convexity of the frontal lobe
are either ascending to the superior sagittal sinus or
descending to the superior sylvian vein. The ascending
veins are frontopolar, anterior frontal, middle frontal, posterior frontal, precentral, and central veins [48,60]. The
ascending veins of the medial frontal surface join the ascending convexity veins along the superior rim of the frontal
lobe to form subdural bridging veins that empty to the superior sagittal sinus [29,48,50,60,65].
The bridging veins, with a diameter of 1 to 4 mm, have a
short free course (5-10 mm) in the subdural space before
entering the superior sagittal sinus [60]. Bridging veins may
enter the sagittal sinus directly, but they may also first join a
meningeal sinus within the dura, with a course of 5 to 30 mm
to the lateral angle of the sagittal sinus [1,48]. A single
meningeal sinus may drain several cortical veins. The dura
may also contain enlarged venous spaces called lacunae,
extending laterally up to 3 cm from the midline. The lacunae
predominantly drain meningeal veins before entering the
sagittal sinus [48]. Most of the cortical veins pass beneath the
lacunae and enter directly into the superior sagittal sinus, but
a few have a common access to the sinus. The lacunae are
largest in the posterior frontal region. Arachnoid granulations often protrude into the floor and walls making them
adherent to the cortical surface (Fig. 5).
The bridging veins pose a serious obstacle to the surgical
approaches into the interhemispheric space. All bridging
veins should be left intact if possible, and sufficient working
space should be searched in between them. The venous
pattern varies highly, but often, a corridor of some
centimeters can be found [48]. The larger the damaged
vein, the higher the risk of venous infarction. Aplastic
superior sylvian vein requires special attention because of
high risk of venous infarction because of reduced venous
collateral flow [50].
Inside the interhemispheric fissure, one may encounter
right and left anterior pericallosal veins side by side on the
corpus callosum, varying highly in size. The pericallosal
veins drain the genu and rostrum of the corpus callosum and
empty into the anterior end of the inferior sagittal sinus. They
should be left intact if possible, but there are often good
venous collaterals.
2.8. Location and orientation of A3As
Fig. 6. Inferior A3A (A), anterior A3A (B), and superior A3A (C) as seen on
sagittal view of CTA.
The A3As originate from the A3 segment at the genu of
corpus callosum, in most cases at the origin of the CMA. The
genu of the corpus callosum is semicircular or oval in sagittal
section with a mean anteroposterior diameter of 11.2 mm
[29]. Consequently, the A3A may occur at 3 principal
locations in the sagittal view as follows: (a) inferior to the
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
141
Fig. 7. Unruptured inferior A3A (arrow) as seen on (A) preoperative 2-dimensional CTA, (B) preoperative 3-dimensional CTA, (C) preoperative MRI, and (D)
postoperative CTA (see Supplementary video A3A-1).
genu of the corpus callosum, often at the A2-A3 junction
(inferior A3A); (b) anterior to the genu of the corpus
callosum, on the central part of the A3 (anterior A3A); and
(c) superior to the genu of the corpus callosum, close to the
A3-A4 junction (superior A3A) (Figs. 2 and 6). Anterior
A3As are the most frequent and the superior A3As the least.
For each of the 3 locations, the interhemispheric approach
should be so directed that the genu does not obstruct the view
to the A3A base. Inferior A3As are usually directed forward,
anterior A3As forward or upward, and superior A3As
upward (Fig. 6A-C).
3. Imaging of A3A
Digital subtraction angiography is still the present gold
standard in many centers. Multislice helical CTA is the
primary modality in our center as noninvasive, safe, and
quick imaging method with a comparable sensitivity and
specificity as DSA in aneurysms larger than 2 mm
[17,25,26,64,73,81,83,84]. Computed tomographic angiography provides more information on the vascular anomalies
of the ACA region, and it allows the disclosure of
calcifications in the arterial walls and quick reconstruction
of 3-dimensional images [28]. The CTA data are used for
quick reconstruction of 3-dimensional images that show, for
example, the surgeon's view of A3A, the relationship with
the corpus callosum. Intracerebral hematomas are usually
frontal, either unilateral or bilateral, sometimes with an
intraventricular component.
For intraoperative navigation toward the A3As, 3dimensional CTA or DSA reconstructions should be
evaluated for the bilateral angioarchitecture of the A2-A3
region and its variations and anomalies; the number of
pericallosal arteries; the correct parent artery (right or left)
and its diameter; distance of the A3A from the A1-A2
junction; orientation of the dome; branching arteries at the
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Fig. 8. Ruptured anterior A3A (arrow) as seen on (A) preoperative sagittal CTA, (B) preoperative coronal CTA, (C) preoperative 3-dimensional CTA, and (D)
postoperative CTA.
A3A neck; location of the A3A with respect to the genu of
the corpus callosum; and distances to the A3 segment and the
A3A from the cortical surface (Figs. 3, 7-9). In addition to
DSA and CTA, in unruptured A3As, T2-weighted MRI
images may be helpful in preoperative planning (Fig. 7C). In
the workstation, 3-dimensional CTA images can be rotated
accordingly to show the surgeon's view and to design a
suitable bony exposure. Intracerebral hematoma may
dislocate the interhemispheric fissure.
4. Microsurgical strategy with A3As
The A3As are rather unusual, and it may be difficult to
gain experience in their microneurosurgical treatment
[4,9,21,23,35,36,40,42,45,47,56,66,71,85,88,90]. Nevertheless, clipping is shown to be an efficient and long-lasting
treatment of distal ACA aneurysms [37]. The A3As pose
certain unique problems and require a different surgical
trajectory than other anterior circulation aneurysms. The
A3As are difficult to reach. The optimal and properly
directed trajectory (inferior vs anterior vs superior A3A)
requires detailed knowledge of the microsurgical anatomy of
the A2-A4 region and careful study of images. The anterior
interhemispheric approach requires tedious dissection
deep in the narrow space, with poor control of the parent
A3. The technique of clipping ruptured or unruptured A3A
is almost the same. The only real difference is the lack of
working space in acute SAH that makes the whole procedure
more difficult.
Yaşargil [88] listed special features of A3As as follows:
(1) lack of working space in the interhemispheric space and
pericallosal cistern; (2) dense adhesion between the cingulate
gyri making separation and finding the aneurysm difficult;
(3) sclerotic wall and broad base of the aneurysm; (4) origin
of branching arteries at the neck and attachment of the dome
to the opposite pericallosal artery; (5) difficult preoperative
decision on the parent A3; (6) attachment or embedding of
the dome in the pial layer of the cingulate gyrus; and (7)
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
143
Fig. 9. Unruptured anterior A3A (small arrow) and unruptured superior A3A found on the same pericallosal artery as seen on CTA in (A) sagittal view, (B)
coronal view, (C,D) 3-dimensional reconstructions.
location of the aneurysm at the bifurcation of an azygos
pericallosal artery. We wish to add the following: (8) saving
the bridging venous system; (9) frontal expansive ICH; (10)
frequent intraoperative ruptures; (11) difficult proximal
control, particularly in inferior A3As below the genu of the
corpus callosum; (12) small size of aneurysm making correct
clip placement difficult; and (13) difficult dissection and
orientation inside the interhemispheric fissure because of
thick blood clots in acute SAH.
4.1. Neuroanesthesiological principles
A general review of our neuroanesthesiological principles
has been published previously [59].
4.2. Intracerebral hematoma
Ruptured A3As are frequently associated with ICH, 28%
in the Kuopio series (Table 3), and the narrow CSF space and
adhesions may add to this. The ICH is usually frontal and can
be located on either side (Fig. 3A-B). We remove massive
ICHs when feasible. Frontal ICHs are likely to cause late
cognitive deficits [70].
4.3. Acute hydrocephalus
In case of acute hydrocephalus, 33% in the Kuopio series
(Table 3), ventricular drainage can be applied to reduce ICP
and to lower the risk of brain damage, in most cases after
immediately securing the ruptured aneurysm. Before or after
clipping, additional CSF can be released, through a small
callosotomy into the lateral ventricle.
4.4. Approach and craniotomy
The A3As are approached through the anterior interhemispheric approach [86,88]. The exposure depends on the
course of the pericallosal arteries, the location of A3A in
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M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
relation to the genu of the corpus callosum, projection of the
dome, and possible ICH. For a right-handed neurosurgeon,
the right-sided approach is more convenient because both
A3s can be reached under the inferior margin of the falx. A
Table 6
Videos on microsurgical management of IAs in this and previous
publications of the series
Aneurysm and publication
Video
Proximal MCA aneurysms
(M1As) [8]
Craniotomy and exposure (LSO)
(M1A-1, Hernesniemi)
Clipping of temporally oriented M1A
(M1A-2, Hernesniemi)
Clipping of frontally oriented M1A
(M1A-3, Hernesniemi)
Clipping of giant M1A
(M1A-4, Hernesniemi)
Clipping of intertruncal-type MbifA
(MbifA-1, Hernesniemi)
Clipping of inferior-type MbifA
(MbifA-2, Hernesniemi)
Clipping of lateral-type MbifA
(MbifA-3, Hernesniemi)
Clipping of insular-type MbifA
(MbifA-4, Hernesniemi)
Contralateral approach to bilateral
MbifAs (MbifA-5, Hernesniemi)
Clipping of MdistA
(MdistA-1, Hernesniemi)
Clipping of MdistA
(MdistA-2, Hernesniemi)
Craniotomy and clipping of A1A
(A1A-1, Hernesniemi)
Craniotomy and clipping of fusiform
A1A (A1A-2, Hernesniemi)
Contralateral approach to A1A
(A1A-3, Hernesniemi)
Clipping of downward ACoAA
(AcoAA-1, Hernesniemi)
Clipping of forward ACoAA 1
(AcoAA-2, Hernesniemi)
Clipping of forward ACoAA 2
(AcoAA-3, Hernesniemi)
Clipping of intertruncal ACoAA
(AcoAA-4, Hernesniemi)
Clipping of backward ACoAA
(AcoAA-5, Hernesniemi)
Clipping of large complex ACoAA
(AcoAA-6, Hernesniemi)
Clipping of double ACoAA
(AcoAA-7, Hernesniemi)
Interhemispheric approach for high
ACoAA (AcoAA-8, Hernesniemi)
Clipping of fusiform ACoAA
(AcoAA-9, Hernesniemi)
Craniotomy for interhemispheric
approach (A2A-1, Hernesniemi)
Clipping of proximal A2 trunk A2A
(A2A-2 Hernesniemi)
Clipping of distal A2 trunk A2A
(A2A-3, Hernesniemi)
Clipping of distal frontopolar artery A2A
(A2A-4, Hernesniemi)
MCA bifurcation aneurysms
(MbifAs) [7]
Distal MCA aneurysms
(MdistAs) [6]
Proximal ACA aneurysms
(A1As) [5]
Anterior communicating artery
aneurysms (ACoAAs)
A2 segment and frontobasal
aneurysms of ACA (A2As)
Table 6 (continued)
Aneurysm and publication
Video
A3 segment ACA aneurysms
(A3As) in this issue
Clipping of unruptured inferior A3A
(A3A-1, Hernesniemi)
Clipping of unruptured inferior A3A
(A3A-2, Hernesniemi)
Clipping of unruptured anterior A3A
(A3A-3, Hernesniemi)
Clipping of ruptured anterior A3A
(A3A-4, Hernesniemi)
LSO indicates lateral supraorbital approach.
left-sided ICH or left-sided–associated anterior circulation
aneurysms may require a left-sided approach. Importantly,
the inferior A3As require a more anterior bone flap than the
anterior A3As or the superior A3As. With wrong angle of
approach, the genu will obstruct neurosurgeons' view toward
the A3A base and prevent proper clip placement. We
measure position of the A3A in relation to the outside
cranium for the exact head positioning and bone flap
placement. Usually the shortest route is selected. Some
authors have used the bifrontal basal anterior interhemispheric approach [4,72]. We feel that the unilateral approach
is less invasive and quicker and provides equal exposure to
the A3As, deep in the interhemispheric fissure.
The interhemispheric approach has been presented on
video in our previous article on A2As (Table 6). The patient is
in supine position with the head fixed in a head frame and
elevated about 20° above the heart level. The head should be
in neutral position with the nose pointing exactly upward.
The head is slightly flexed or extended according to the
location of the A3A with respect to the genu of corpus
callosum. In the correct head position, the trajectory is almost
vertical. Tilting the head to either side increases the chance
that the bone flap is placed too laterally from the midline. This
would make the entrance into the interhemispheric fissure
and navigation there more difficult. If intraoperative DSA is
considered, the frame pins should be placed accordingly. It is
our practice to adjust the position of the fixed head and body
during the operation when needed [20].
After minimal shaving, an oblique skin incision with its
base frontally is made just behind the hairline, over the
midline, extending more to the side of the planned bone flap.
Location, curvature, and extent of skin incision depend on
the hairline, dimensions of the frontal sinuses, and the
orientation of the A3A. A 1-layer skin flap is reflected
frontally with spring hooks. Bicoronal skin incision is
unnecessary because strong retraction with hooks often
allows anterior enough exposure of the frontal bone. The
bone flap is placed slightly over the midline to allow better
retraction of the falx medially. The superior sagittal sinus
may deviate laterally from the sagittal suture, more often to
the right, and as far as 11 mm [75]. The size of the bone flap
depends both on the surgeon's experience and on the
presence of ICH. We usually use a 3 to 4 cm diameter flap. A
too small flap may not provide sufficient room for working
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
between the bridging veins. In most patients, only one burr
hole in the midline over the superior sagittal sinus at the
posterior border of the bone flap is needed. Through this
145
hole, bone can be detached from the underlying dura. One
has to be careful with the underlying sagittal sinus,
particularly in the elderly with very adherent dura. The
Fig. 10. Intraoperative picture of the interhemispheric fissure with CMA and the tightly attached (A) cingulate gyri (CG), (B) rolled cottons used as expanders,
(C) pericallosal artery (PerA) in between the CG, and (D) white color of the genu of corpus callosum (CC) (see Supplementary video A3A-2).
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M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
bone flap is removed using a side cutting drill. High-speed
drill can be used to smooth the edges or to enlarge the
opening if necessary.
The dura is opened under a surgical microscope as a
C-shaped flap with its base at the midline. The incision is first
made in the lateral region and then extended toward the
midline in the anterior and the posterior direction to prevent
opening of the superior sagittal sinus. The dural opening
should be planned so that possible meningeal sinuses and
lacunae are left intact. Bridging veins may be attached to the
dura for several centimeters along the midline. Careful
dissection and mobilization of these veins is necessary. It is
usually during the opening of the dura that unwelcome damage
to the bridging veins takes place. Dural edges are elevated with
multiple stitches extended over the craniotomy dressings.
4.5. Removal of ICH
In case of large ICH and lack of space (Fig. 3A-B), a
small cortical incision is made accordingly, and hematoma is
partially evacuated to gain space. This may risk the rerupture
of A3A that would be difficult to control through the ICH
cavity. In removing the ICH clot, before or after clipping,
only minor force should be applied not to sever perforating
arteries. Intracerebral hematoma in the immediate vicinity of
the aneurysm should be left in place until the proximal and
the distal control have been obtained.
In acute SAH, thick blood clots inside the interhemispheric fissure make dissection and visualization of the A3A
and the parent artery difficult. Successive irrigation with
saline (“water dissection”) and gentle suction can be used to
flush the clots out and to provide better room for further
dissection. Only the blood clots that obstruct the approach
trajectory are removed. Too extensive removal can easily
damage the surrounding brain tissue.
4.6. Cerebrospinal fluid drainage
The callosal cistern is shallow and not much CSF can be
removed during interhemispheric approach. In unruptured
A3As, this space will usually do. In acute SAH, CSF can be
released by a puncture to the lateral ventricle at the lateral
border of craniotomy. The alternative is puncturing the
corpus callosum by closed bipolar forceps medial to the
pericallosal artery followed by opening of the forceps to
create a small channel for CSF release. Partial removal of
ICH may also provide enough room.
4.7. Interhemispheric dissection toward A3A
For the interhemispheric approach, the images should be
evaluated for several microsurgical aspects such as depth of
the free margin of the falx; depth of the genu of the corpus
callosum; depth and course of the pericallosal and the
callosomarginal arteries; correct parent A3; location of
the A3A (inferior, anterior, superior); size and orientation
of the dome; and possible dislocations because of ICH.
Computed tomographic angiography should be carefully
reviewed for calcifications in the arteries and the A3A wall.
Calcified plaques in the parent artery will affect temporary
clipping, and those at the dome risk intraoperative rupture
and incomplete closure of the neck.
Upon entering the interhemispheric fissure, bridging
veins may obstruct the view, preventing even the slightest
retraction of the frontal lobe. The veins are likely to restrict
the working space, and one may have to work between them.
It may help to dissect some of them for a few centimeters
from the brain surface that is very difficult. Cutting a few
small branches may allow safe displacement of the major
trunk. One may have to sacrifice a smaller vein, at the risk of
venous infarction though. Extensive and long-lasting use of
retractors, preventing venous flow, may have the same result
as severing of bridging veins.
We use a handheld syringe to expose and to expand
planes and to clean the blood clots for further dissection, that
is, the water dissection technique of Toth [44]. Arachnoid
membranes and strands are cut sharply by microscissors that
can be also used as a dissector when closed. Use of retractors
is kept at minimum, and they are not routinely used at the
beginning of the approach. Instead, bipolar forceps in the
right hand and suction in the left, with cottonoids of different
sizes as expanders, are used as microretractors [20]. When
the interhemispheric fissure is widely opened and the frontal
lobe mobilized, the retractor may be used to retain some
space for clipping, but otherwise avoided. Rolled cottons,
placed inside the interhemispheric fissure at the anterior and
the posterior margin of the approach, provide a more gentle
retraction than classical, mechanical retractors (Fig. 10B).
Inside the interhemispheric fissure, after clearing the
arachnoid adhesions, dissection is directed along the falx
toward the genu of the corpus callosum. It is important to be
aware of the microscope's angle and the exact head position.
With a wrong angle of approach, one gets easily lost inside
the interhemispheric fissure with no good landmarks to guide
toward the aneurysm. At the inferior border of the falx, the
dissection plane is identified between the cingulate gyri
attached to each other (Fig. 10A). The pericallosal artery
may be found already in the cingulate sulcus, but in most
cases the dissection must be continued deeper toward the
corpus callosum, identified by its white color and transverse
fibers (Fig. 10C-D). Taking the attached cingulate gyri as the
corpus callosum or other paired arteries as the pericallosal
arteries leads to serious problems of navigation.
Once inside the callosal cistern, the both pericallosal
arteries are visualized, realizing that they can be on either
side of the midline. The artery that leads to the A3A is
identified and followed to the proximal direction toward the
aneurysm. A tedious and careful dissection is performed in
the deep and narrow proximal interhemispheric fissure. The
aim is to identify the proximal part of the parent A3 trunk.
Landmarks of help are the origin of the callosomarginal
artery, the genu of the corpus callosum, and possible vascular
anomalies recognized in the images. Because the A3A is
approached along the distal parent A3, the dome with its
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
possible rupture site is likely to get in the way, obstructing
the view to the proximal parent A3, the site for temporary
clipping. Premature rupture at this phase, with little room and
no proximal control, may cause great difficulties.
The dome often extends more to one side and is embedded
in the pial layer of the cingulate gyrus. This may allow
traversing along the opposite gyrus to get proximal control of
the parent A3, often the most difficult part of the interhemispheric approach. The direction of the A3A may change
because of retraction, and blood may obscure the anatomy,
making identification of the aneurysm difficult. Strong
retraction is likely to cause intraoperative rupture. We do
not use partial callosal resection to enlarge exposure in the
infracallosal region [10]. With appropriate head positioning
and well-placed bone flap, it is possible to obtain adequate
visualization of the A3As without any callosal resection [31].
In acute SAH, the cingulate gyri are usually very tightly
attached to each other (see Supplementary video A3A-4).
Dissection of the proximal parent artery can cause great
difficulties, and it can easily damage both cingulate gyri. In
such situations, at the expense of poor proximal control, the
aneurysm is approached directly, and pilot clip is placed at
the neck as soon as possible. With the pilot clip in place,
dissection of the dome is continued.
5. Dissection and clipping of A3As
5.1. General principles
Small size, thin wall, and a relatively broad base involving
branches make the dissection of A3As tedious in the narrow
working space. The proximal and the distal parts of parent
arteries as well as all the adjacent branches should be
unhurriedly and painstakingly visualized before the final
clipping. A small subpial resection is often necessary to allow
the mobilization and visualization of the whole A3A dome.
5.2. Dissection under temporary clipping of arteries
Temporary clipping facilitates sharp dissection of the A3A
and the adjacent arteries. Dissection and preparation of the sites
for the temporary clip(s) should be performed with blunttipped bipolar forceps or with microdissector. One temporary
clip, usually a small one, curved or straight, is applied proximal
to the aneurysm. The proximal clip can be close to the
aneurysm, but the distal ones should be in a distance not to
interfere with the visualization and the permanent clipping of
the A3A neck. In ruptured cases, CMA may require its own
temporary clip. When the main part of the base is dissected, a
short, straight pilot clip is applied, and the temporary clip is
removed. When removed, the temporary clip should be first
opened carefully in place to test if any unwanted bleeding
occurs. Removal in rush can be followed by heavy bleeding
and great difficulties in placing the clip back. Furthermore,
while removing the temporary clip, even the slightest
resistance should be noted as a possible involvement of a
small branch in the clip or its applier. If access to the proximal
147
A3 cannot be achieved, direct pilot clipping is the only choice,
usually a small microclip applied to the aneurysm base. Longer
clips may involve or kink side branch(es).
5.3. Clipping of A3A base
A proper selection of clips with different shapes and
lengths of blades and applicators, suiting the imaging anatomy
of the A3A, should be ready for use. A limited selection of
final clips is needed when temporary clipping of the arteries
and bipolar shaping of the aneurysm dome is used. The A3As
are generally small with many surrounding small branches. To
prevent kinking or occlusion of adjacent branches, the
smallest but adequate final clip should be selected. If bipolar
reshaping is not considered, the blade of a single occluding
clip should be one and a half times the width of the base. We
prefer inserting first a pilot clip to the A3A dome, preferring
Sugita clips for their wide opening distance and blunt tips.
The pilot clip is later changed for a smaller and lighter final
clip, after reshaping of the dome by bipolar coagulation. In the
interhemispheric approach, one has to insert the pilot clip at a
rather early phase of dome dissection, if the proximal parent
artery cannot be visualized, or a premature rupture occurs.
Adequate dissection, proper sizes of clips, and painstaking
checking that the clip blades are well placed up to their tips are
required to preserve the adjacent branches. If the first clip
slides, exposing some of the neck, another clip may be applied
proximal to the first one for final closure (“double clipping”).
Removal of the retractors and cottonoids may lead to kinking
of the parent artery or compression of the perforators by the
clip blades or the clip itself. The flow has to be checked once
more and papaverine applied.
5.4. A3A rupture before clipping
The A3As may rupture while entering the interhemispheric
fissure or dissecting the aneurysm base. The risk is high because
most A3As are oriented so that their dome is encountered
before visualization of the proximal artery. The inferior A3As
are particularly problematic for difficult proximal control.
Control should be first attempted via suction and compressing
the bleeding site with cottonoids. We always keep a second
suction prepared and functional. Sudden and short hypotension
by cardiac arrest, induced by intravenous adenosine, can be
used to facilitate quick dissection and application of a pilot clip
in case of uncontrolled bleeding [59]. A pilot clip may be
inserted to a ruptured secondary pouch if visible. Otherwise,
temporary clips are inserted proximally on the parent A3,
possibly also on A3 branches such as CMA, to allow dissection
of the base and final clipping. A small and thin-walled A3A
may rupture at its neck during dissection. In such case, under
temporary clipping, reconstruction of the base involving a part
of the parent A3 in the clip should be attempted.
5.5. Intraoperative verification of clipping
We use micro-Doppler to check the patency of the
proximal and distal arteries and branches, but unexpected
occlusions are sometimes seen in postoperative angiography
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M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
[33]. We routinely use intraoperative noninvasive ICG
infrared angiography [57,58]. It helps the orientation during
dissection, and it visualizes wall thickness and plaques,
perforating arteries, and incomplete neck occlusion. The ICG
angiography reduces the need for invasive intraoperative
angiography for clipping control, but DSA is still required in
giant and complex aneurysms.
trajectory is too anterior, one may become lost down in
the interhemispheric fissure, not identifying the genu. In
addition to the head position, the angle of the microscope
should be checked as well to prevent the wrong approach
angle. The corpus callosum and both A3s are identified
and followed along the curved surface of the genu toward the
A2-A3 junction where the A3A lies.
5.6. Resection of A3A dome
When appropriate, not risking the branching arteries or
other structures, we resect the aneurysm dome for final check
of closure and for research purposes [15,76]. This policy
teaches one to dissect domes more completely and avoid
closure of the perforators.
6.1.5. Clipping
The parent artery should be visualized if possible, without
damaging the cingulate gyri. This may be easier from behind
the A3A than in front of it (Fig. 11). If proximal control
cannot be obtained, pilot clip is placed at the dome, and
under its control, the final dissection is carried out. The pilot
clip is exchanged for the smallest possible final clip. Care is
taken not to occlude branch(es) at the A3A base.
6. Considerations for individual A3A location
6.2. Anterior A3As
6.1. Inferior A3As
6.2.1. Planning
The anterior A3As are located at the midsection of the A3
segment, anterior to the genu of corpus callosum (Fig. 8A-D,
see Supplementary videos A3A-3 and A3A-4). The genu
does not obstruct the base of the anterior A3As as much as in
the inferior A3As, so it is somewhat easier to obtain proximal control. The anterior A3As are usually oriented forward and upward.
6.1.1. Planning
The inferior A3As are located at the junction of the A2 and
A3 segments, inferior to the genu of the corpus callosum
(Fig. 7A-D; see Supplementary videos A3A-1 and A3A-2).
They require more anterior approach than the other A3As so
that the genu does not obstruct the view toward the base.
Inferior A3As usually point forward and slightly upward, with
possible deviation to either side. Proximal control is
particularly difficult to obtain in the inferior A3As. Because
of their deep location and poor proximal control, inferior A3As
are usually more difficult clip than anterior or superior A3As.
As a rule, the more proximal the A3A lies, the more difficult
the clipping is going to be as one has to work deeper in a
narrower corridor.
6.1.2. Head position
The head should be in neutral position with the nose
pointing exactly upward with slight extension of the neck.
No rotation or lateral tilting is allowed.
6.1.3. Skin incision and craniotomy
After minimal shaving, an oblique skin incision with its
base frontally is made just behind the hairline, over the midline,
extending more to the side of the planned bone flap. Location
and extent of skin incision depends on the hairline, dimensions
of the frontal sinuses, and the orientation of the inferior A3A. A
1-layer skin flap is reflected frontally with spring hooks.
Bicoronal skin incision is unnecessary because strong retraction with hooks often allows anterior enough exposure of
the frontal bone. Paramedian frontal craniotomy is performed
as anterior as possible without opening the frontal sinuses. If
this happens, the sinuses should be packed and isolated with
fat or muscle grafts and covered with pericranium.
6.1.4. Dissection toward the aneurysm
Inside the interhemispheric fissure, the dissection is
directed along the falx toward the anterior margin of the
genu of the corpus callosum that is the first landmark. If the
Fig. 11. Proximal control of the parent pericallosal artery (PerA) can be
obtained from below the A3A.
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
6.2.2. Head position
The head should be in neutral position with the nose
pointing directly upward with none or only slight flexion and
with no rotation or lateral tilting.
6.2.3. Skin incision and craniotomy
An oblique skin incision is made behind the hairline in
front of the coronal suture with the base frontally.
Paramedian craniotomy is located more posteriorly than for
the inferior A3As. The approach angle should point directly
toward the aneurysm.
6.2.4. Dissection toward the aneurysm
Dissection in the interhemispheric fissure is first directed
toward the genu of corpus callosum and after both A3s have
been identified the appropriate A3 is followed in the proximal
direction. The dissection is directed around the aneurysm
dome, and proximal A3 is exposed if possible.
6.2.5. Clipping
Final, sharp dissection of the base and the dome is
performed with the help of temporary clips. If proximal
control cannot be obtained, pilot clip is placed at the dome,
and under its control, the final dissection is carried out. The
pilot clip is exchanged for the smallest possible final clip to
prevent kinking.
6.3. Superior A3As
6.3.1. Planning
The superior A3As, the least frequent of the A3As, are
located at the distal part of the A3 segment, superior to the
genu of the corpus callosum (Fig. 9A-D). The genu does not
obstruct the approach trajectory and the parent proximal A3
can be usually visualized for temporary control. Superior
A3As are often directed upwards, even backwards.
6.3.2. Head position
The head should be in neutral position with the nose
pointing directly upward, with little flexion and no rotation
or lateral tilting.
6.3.3. Skin incision and craniotomy
Skin incision is made behind the hairline in front of the
coronal suture with the base frontally. The craniotomy is
almost the same as in the anterior A3As. The approach angle
should point directly toward the aneurysm.
6.3.4. Dissection toward the aneurysm
Dissection in the interhemispheric fissure is directed
toward the corpus callosum, which is identified along with
the both A3s and followed proximally. In superior A3As, it is
possible to arrive almost directly at the base of the aneurysm.
Exposure of the parent A3 should be easier than in more
proximal A3As. Dissection of the aneurysm is continued
under proximal control.
6.3.5. Clipping
The whole aneurysm base is dissected free, and all the
originating branches are visualized. We usually open and
149
coagulate the aneurysm dome and then replace the pilot clip
with final clip that should be as small and light as possible.
7. Associated aneurysms
The A3As are often associated with other aneurysms
[9,21,36,47,56,88,90]. In our series, 58% of our 163 A3A
patients, and 36% of the 97 with ruptured A3A had at least
one additional aneurysm (Table 5). Multiple A3As were seen
in 24 patients. Most A3As can be reached under falx even if
they are on the contralateral side to the craniotomy. Bilateral
interhemispheric approach is not necessary. Our strategy is to
clip all aneurysms that can be exposed through the same
approach, that is, in this case only DACA aneurysms. This
may not be advisable if clipping of the ruptured aneurysm is
difficult or the brain is swollen because of acute SAH [9,62].
This technique of clipping multiple aneurysms at different
locations is not recommended at early learning curve. In
acute SAH, if there are problems in clipping the ruptured
aneurysm, one should not continue with the unruptured one
(s). We do not recommend multiple craniotomies for
ruptured cases in the acute phase.
8. Giant A3As
Giant A2 to A5 (pericallosal) aneurysms of are extremely
rare, less than 20 published cases [11-13,18,21,36,39,46,49,
53,54,67,71,74,77]. There was only one giant A3A in our
series of 4253 aneurysms (Table 3). Giant A3As may mimic
symptoms of frontal tumors. Magnetic resonance imaging
and DSA are essential for correct diagnosis. Clipping is
considered if A3 and its branches are not heavily involved in
the base. Removal of intraluminal thrombus under temporary
clipping may be necessary to decompress the aneurysm base
for the application of the final clip(s). If direct clipping does
not seem possible, bypass and subsequent proximal occlusion of the parent A3 may be considered [30,32,51].
9. Fusiform A3As
Fusiform A3As are extremely rare, none in our series.
Wrapping, proximal occlusion, excision, trapping, parent
artery occlusion with preoperative bypass, and reconstruction can be considered [63].
10. Bypass operations and arteriotomies
Preoperative bypass, side-to-side A3-A3 bypass, or
arterial translation (eg, STA-ACA) may be considered in
giant or fusiform A3As [30,32,51]. Acute SAH makes
bypasses extremely demanding. A comprehensive neurovascular team should be prepared to perform intraoperative
arteriotomies, for example, to remove coils or thrombi, and
intraoperative bypasses, also in case of emergency.
150
M. Lehecka et al. / Surgical Neurology 70 (2008) 135–152
Acknowledgments
Authors thank Mr Ville Kärpijoki for his excellent
technical assistance.
Appendix A. Supplementary Data
Supplementary data associated with this article can be found,
in the online version, at doi:10.1016/j.surneu.2008.03.019.
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