Keywords
pericallosal aneurysm - endovascular management
Palavras-chave
aneurisma pericaloso - manejo endovascular
Introduction
Distal anterior cerebral artery (DACA) aneurysms, also called pericallosal or A2 aneurysms,
are rare and comprise ∼ 1.5 to 9% of all intracranial aneurysms. The ideal treatment
should be aggressive occlusion due to the high tendency of rupture ([Fig. 1]).[1]
[2]
[3]
Fig. 1 Aneurysms of the pericallosal-callosomarginal junction. Source: Mann et al.[2] (1984).
Despite the classical microsurgical approach to those lesions, recent improvement
on radiological equipment and modern endovascular techniques provided new options
for the treatment of wide neck aneurysms, overcoming the vulnerability to rupture
during the operative exposure, and increasing the rate of success with this technique
to 92.2–100%.[3]
[4]
[5]
[6]
[7]
Since 2005, at our institution, we have been choosing the endovascular coiling technique
for the treatment of all pericallosal artery aneurysms, including those associated
with intracerebral hemorrhage (ICH). In order to investigate the safety and efficacy
of this method when treating DACA aneurysms, we report the outcomes of the aneurysms
coiled at our service and compare them with series of microsurgical treatment.
Material and Methods
Our institution is a tertiary medical center serving an area of middle valley in the
state of Santa Catarina, Southern Brazil, with a population of 750,000 people. We
conducted a retrospective cohort study including patients admitted to the hospital
from October 2005 to March 2015. During this period, 1,092 patients with ruptured
or unruptured aneurysms underwent endovascular procedures. This material was organized
as a historical cohort that was statistically analyzed and compared with some pericallosal
aneurysms series extracted from the database.
The post-procedural outcomes were measured using the modified Rankin scale (mRS, [Table 1]) at discharge. An mRS score ≤ 2 for ruptured aneurysms or no change from baseline
for unruptured aneurysms was considered a good clinical outcome.[27]
Table 1
Modified Rankin Scale.
|
Modified Rankin Scale
|
|
0
|
No symptoms
|
|
1
|
No significant disability, despite symptoms; able to perform all usual duties and
activities.
|
|
2
|
Slight disability; unable to perform all previous activities but able to look after
own affairs without assistance.
|
|
3
|
Moderate disability; requires some help, but able to walk without assistance.
|
|
4
|
Moderately severe disability; unable to walk without assistance and unable to attend
to own bodily needs without assistance.
|
|
5
|
Severe disability; bedridden, incontinent, and requires constant nursing care and
attention.
|
|
6
|
Death.
|
Source: van Swieten et al.[27] (1988).
The angiographic demographic variables consisted on: ruptured/unruptured state; aneurysm
size defined by long-axis measurement; and neck size and initial occlusion results.
Every procedure was performed on a monoplane C-arm angiographic system without 3D
reconstruction. A procedure-related rupture was considered present if there was an
extravasation of contrast during the coil embolization. A transcranial Doppler was
performed for the diagnosis and outcome of the vasospasm. All aneurysms were treated
using platinum coils or stent-assisted coiling. Only one neurosurgeon performed every
procedures (LJH).
The patients with ruptured aneurysms were evaluated by clinical grade Hunt-Hess ([Table 2]) and Fischer scales for computed tomography ([Table 3]). Furthermore, a neck size ≥ 4 mm indicates a wide-neck aneurysm, and the patients
were divided into two groups: those with neck diameters < 3 mm and those with neck
diameters ≥ 3 mm. Re-ruptured aneurysms did not occur by this casuistic. The statistical
analysis was performed with the chi-square test, considering as statistically significant
values of p < 0.05.
Table 2
Hunt and Hess grading system for patients with subarachnoid hemorrhage
|
Grade
|
Neurologic status
|
|
1
|
Asymptomatic or mild headache and slight nuchal rigidity.
|
|
2
|
Severe headache, stiff neck, no neurologic deficit, except cranial nerve palsy.
|
|
3
|
Drowsy or confused, mild focal neurologic deficit.
|
|
4
|
Stuporous, moderate or severe hemiparesis.
|
|
5
|
Coma, decerebrate posturing.
|
Note: Based upon initial neurologic examination; adapted from Hunt, Hess[28] (1968).
Table 3
Fisher grade of cerebral vasospasm risk in subarachnoid hemorrhages
|
Group
|
Appearance of blood on head CT scan
|
|
1
|
No blood detected.
|
|
2
|
Diffuse deposition or thin layer with all vertical layers (in the interhemispheric
fissure, the insular cistern, the ambient cistern) less than 1 mm thick.
|
|
3
|
Localized clot and/or vertical layers 1 mm or more in thickness.
|
|
4
|
Intracerebral or intraventricular clot with diffuse or no subarachnoid blood.
|
Abbreviation: CT, computed tomography.
Source: Fisher et al.[26](1980).
Results
Since 2005, our institution treated 1,092 patients with coiling aneurysms, with 2.74%
(n = 31) of them corresponding topography of DACA aneurysms, all confirmed on digital
subtraction angiography (DSA). The demographic characteristics showed that the majority
of patients were female (n = 23), and their average age was 54.6 years ([Table 4]). Twenty one (67%) patients presented with ruptured aneurysms, and 13 (61%) suffered
clinical or radiological vasospasms. The analysis of the mRS scores at discharge of
these ruptured aneurysms showed: 10 patients (47%) with mRS scores ≤ 2; mRS 3–5 in
7 patients (33%), and 4 deaths (19%, mRS 6) caused by severe vasospasm.
Table 4
Ruptured versus unruptured, characteristics
|
Ruptured, n
|
Unruptured, n
|
|
Totals
|
21
|
10
|
|
Mean age
|
53
|
57
|
|
Sex
|
|
|
Male
|
6
|
2
|
|
Female
|
15
|
8
|
|
Clinical presentation
|
|
Hunt-Hess I-II
|
15
|
|
|
Hunt-Hess III
|
4
|
|
|
Hunt-Hess IV-V
|
2
|
|
|
Aneurysm size
|
|
< 10 mm
|
19
|
9
|
|
≥ 10 mm
|
2
|
1
|
|
Modified Fischer score
|
|
1 - 2
|
9
|
|
|
3
|
6
|
|
|
4
|
6
|
|
|
Hospitalization (days)
|
|
Average length
|
6
|
2
|
|
Rankin (mRs)
|
|
0 - 2
|
10
|
|
|
3 - 5
|
7
|
|
|
6
|
4
|
|
Abbreviation: mRS, modified Rankin Scale.
None of the ruptured aneurysms required emergency decompressive craniotomy or hematoma
evacuation to avoid brain herniation, even though three patients presented hematoma.
Twenty eight patients had small aneurysms (< 10 mm in maximum diameter), and 6 of
them were < 3 mm. Another important variable to investigate is the size of the neck
of aneurysm. In our study, all neck sizes were ≤ 4 mm.
The patients were treated with coiling. Only one could not be treated (because of
a proximal vasospasm), and this was considered a failure of treatment. No periprocedural
symptomatic complications occurred. The immediate angiographic results showed complete
aneurysm occlusion in all 30 cases of coil-treated aneurysms. There were thirteen
controlled aneurysms, and angiographic obliteration was achieved in twelve of them
with one year of follow-up. There was only one recanalization, which was recoiled
immediately.
Discussion
The guidelines for the proper management of DACA aneurysms has changed over the past
years, mainly due to improvements on the techniques, which were able to ensure security
and minimal invasive procedures. In our institution, we have been performing endovascular
coiling for unruptured and ruptured DACA aneurysms, including those associated with
ICHs, as the first-line treatment.[7]
[8]
[9]
[10]
The most frequently reported site for aneurysms is the anterior communicating artery,
which represents 36% of cases. Other locations include the middle cerebral artery
(26%), the posterior communicating artery (18%), and the internal carotid artery (10%).
Our database differs, with 20% of aneurysms of the posterior communicating artery,
18% of the anterior communicating artery, and 14% of the middle cerebral artery. Distal
anterior cerebral artery aneurysms correspond to 2.74% of the total; it may not represent
much, but the approach to them is changing, and we have been working to achieve security
and efficacy with the endovascular treatment.[11]
[12]
[13]
Payner et al, in a cohort with 2,411 patients with aneurysms treated between 1998
to 2009, stated that the proportion of anterior communicating artery aneurysms managed
with endovascular coiling increased from 6% to 38%. Overall group comparisons showed
no statistically significant difference between the average length of hospitalization
for the patients who underwent endovascular coiling or clip ligation for their ruptured
and unruptured aneurysms. In our institution, for the unruptured group, the average
length of hospitalization is of two days for the coiling of aneurysms; in contrast,
the unruptured group who underwent clipping had an average hospital stay of six days.[13]
The International Subarachnoid Aneurysm Trial (ISAT) demonstrated in 2002 that endovascular
coiling for ruptured aneurysms with detachable coils was superior to surgical clipping
by showing that a lower proportion of patients were dead or disabled after 1 year.
We verified 4 (19%) deaths (mRS 6) by vasospasm within 21 cases of subarachnoid hemorrhage
(SAH), which is slightly larger than the percentage found in our database (13%) for
other aneurysm locations. Approximately 70% of the patients in this paper had SAH,
which probably contributes to the relatively high mortality rates (19%) reported with
the endovascular treatment of pericallosal aneurysms.[14]
[15]
[16]
Based at our casuistic, when a comparison is made with the posterior communicating
aneurysm, knowing it has an easy location for endovascular treatment, we testified
similar rates of immediately occlusion. We found 96% immediate occlusion in 31 pericallosal
aneurysms ([Figs. 2] and [3]) excluding only due impossibility to access, this patient died due catastrophic
vasospasm. This rate is superior to the one found by Keston (82%) and Bilstra et al
(89%). In a surgical series, complete clipping of the aneurysmal neck was achieved
in 90% of patients.[11]
[17]
Fig. 2 Angiogram of a ruptured pericallosal aneurysm in a female patient, age 56. Lateral
(A), anteroposterior (B) and lateral zoom (C) views of a selective injection of a
right internal carotid artery.
Fig. 3 Angiogram of a ruptured pericallosal aneurysm in a female patient, age 56, post embolization.
Lateral (A), anteroposterior (B) and lateral zoom (C) views of a selective injection
of the right internal carotid artery.
In the study conducted by Hui et al, when outcomes were dichotomized to mRS 0–2 versus
3–6, there was a statistically significant difference, with coiling being more likely
to produce a good outcome in patients with SAH. In the same study, all electively
coiled pericallosal aneurysms (100%) had an mRS score of 0, and there was 1 patient
(5%) with an mRS score of 4, and five patients (25%) with mRS scores of 1–2 in the
clipped group. Regarding patients with SAH, 61% (13/21) presented vasoespasms ([Fig. 4]), and 47% (10/21) presented a good recovery (mRS 0–2), with moderate disability
in 33% (7/21) (mRS 3–5) and a 19% (4) mortality rate. In a surgical series, the author
Orz described the outcome for15 patients with ruptured aneurysms, he obtained Glasgow
Outcome Scale between 1 and 4 (moderate disability and death) in 46%, against 52%
(11/21) reported in our series.[3]
[8]
[9]
[18]
Fig. 4 Angiogram of a ruptured pericallosal aneurysm in a female patient, age 46, with an
A1 vasospasm. Anteroposterior (A) and lateral (B) views of a selective injection of
the left internal carotid artery.
Furthermore, in surgical groups, the aneurysmal neck was completely occluded without
a residual neck in 90% of patients, while our series demonstrated 96% of complete
occlusion. Small aneurysms corresponded to 90% of the cases (n = 28) in our study. All DACA aneurysms, even if very small in size or discovered
accidentally, should be aggressively treated because of their high tendency to rupture.
To achieve security in surgery, Treynelis and Dunker proposed an interhemispheric
approach with partial resection of the genu corpus callosum to achieve the proximal
control, however this has made the approach aggressive. Several studies report that
DACA aneurysms were considered a surgical challenge due to certain specific characteristics
when compared with aneurysms located elsewhere.[3]
[4]
[9]
[17]
[19]
We treated ten unruptured aneurysms without periprocedural complications. Distal anterior
cerebral artery aneurysms are usually small, and bleeding occurs irrespective of their
size because of the lack of resistant arachnoid membranes at the level of the pericallosal
cisterns.[3]
[9]
[17]
[19]
[20] Therefore, we need to be aggressive, without complication, even Sturiale demonstrated
in a systematic review a rate nearly 7% of overall periprocedural rupture, with a
procedure related morbidity rate of 8%, higher than that of other circle of Willis
aneurysms.[7]
[21]
[22]
[23]
Comparing the technical challenges posed by the endovascular management and clipping,
both techniques present difficulties. Pericallosal artery aneurysms at the bifurcation
represent a special endovascular technical challenge given their distal location,
commonly wide-neck morphology, small parent vessel diameter and potentially high recurrence
rate after coiling given the bifurcation location. But the microsurgical approach
to peri + callosal aneurysms was considered difficult, because the proximal control
is achieved relatively late in the dissection, and the dissection must take place
throughout a very narrow and deep corridor.[3]
[9]
[17]
[19]
[24]
The introduction of new malleable microcatheters and microguidewires with improved
trackability, pushability, and torque, together with the application of hydrophilic
coating, has made the navigation into distant cerebral arteries easier. This possibility
of associated techniques to occlude the aneurysm, such as, stent-assisted coiling
([Fig. 5]), in the study conducted by Darkhabani et al, could treat four patients with a Y-configuration
stent-assisted coil embolization technique; all patients were successfully treated
without significant technical difficulties.[24]
[25]
Fig. 5 Angiogram of an unruptured pericallosal aneurysm in a female patient, age 67, with
multiple aneurysms. Lateral (A) and anteroposterior (B) views of a selective injection
of the right internal carotid artery with a stent-assisted coiling technique.
In our cases, no patients had large hematomas requiring emergency decompressive craniotomy
or hematoma evacuation. Follow-up after one year was conducted in thirteen cases ([Fig. 6]), with only one recanalization, which was immediately recoiled. Nguyen et al emphasized
the recurrence rate of coiled DACA aneurysms, even though the rate was not significantly
higher than the one for intracranial aneurysms coiled elsewhere. In a review of an
ISAT cohort with 18 years of follow-up, Molyneux et al reported a small excess risk
of subarachnoid hemorrhage recurrence from the target aneurysm in the endovascular
group up to 17 years after the initial hemorrhage. However, this excess did not translate
to a significantly worse clinical outcome when compared with the surgically treated
group. The overall risk of death or dependency from a new bleeding did not differ
between the groups.[14]
[16]
[23]
Fig. 6 Angiogram of a ruptured pericallosal aneurysm in a female patient, age 46, after
1 year of follow-up. Anteroposterior (A) and lateral (B) views of a selective injection
of the left internal carotid artery.
Conclusion
The endovascular management of DACA aneurysms has shown to be a safe technique, with
good results, and it is performed in several centers worldwide. The same approach
is followed for the presence of ICHs. The initial results of ISAT 2002 for the endovascular
coiling in pericallosal artery aneurysms were not satisfactory, but we actually saw
encouraging results regarding distal aneurysms. Microsurgical clipping is still the
primary treatment modality for DACA aneurysms, however endovascular treatment shall
be considered a good method.
