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Vol. 25. Num. 2.March - April 2014Pages 49-98
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Vol. 25. Num. 2.March - April 2014Pages 49-98
Case report
DOI: 10.1016/j.neucir.2013.04.002
Coil embolization of ruptured frontopolar artery aneurysm: Case report
Tratamiento endovascular de aneurisma roto en arteria frontopolar: caso clínico
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Ana M. Castaño-Leona,??
Corresponding author
, Marta Cicuendeza, Igor Paredesa, Jose F. Alena, Pedro Naviab, Alfonso Lagaresa
a Departamento de Neurocirugía, Hospital 12 de Octubre, Madrid, Spain
b Departamento de Radiología, Hospital 12 de Octubre, Madrid, Spain
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Abstract

Distal anterior cerebral artery aneurysms are infrequent. The most common location is at the bifurcation of the pericallosal and callosomarginal arteries. Cerebral artery anomalies can sometimes, at least partially, explain aneurysm formation in less common locations in relation to hemodynamic stress caused on the vascular wall. We report a very rare case of subarachnoid hemorrhage due to a ruptured frontopolar artery aneurysm as a part of an anomalous anterior cerebral artery complex that was, for the first time, treated with endovascular coiling.

Keywords:
Subarachnoid hemorrhage
Frontopolar artery
Aneurysm
Endovascular treatment
Hemodynamic stress
Cerebral vascular anomaly
Resumen

Los aneurismas distribuidos distalmente en la circulación cerebral anterior son infrecuentes. La localización más habitual dentro de este tipo de aneurismas es la bifurcación entre las arterias pericallosa y callosomarginal. Las variantes anatómicas vasculares cerebrales pueden explicar, al menos en parte, la formación de aneurismas en localizaciones menos comunes en relación al estrés hemodinámico que ocasionan en la pared vascular. Describimos un caso infrecuente de hemorragia subaracnoidea debida a la rotura de un aneurisma en la arteria frontopolar y que forma parte de una variante anómala del complejo de la arteria cerebral anterior que ha sido por primera vez manejado mediante tratamiento endovascular.

Palabras clave:
Hemorragia subaracnoidea
Arteria frontopolar
Aneurisma
Tratamiento endovascular
Estrés hemodinámico
Variante anatómica vascular
Full Text
Introduction

Distal anterior cerebral artery (DACA) aneurysms are those located after anterior communicating artery, also known as pericallosal artery aneurysms. The incidence of saccular aneurysms in DACA is low, representing about 6% (range 2–9%) of all intracranial aneurysms. The most common location of DACA aneurysms is the A3 segment, accounting for approximately 69–82% of all DACA aneurysms, especially at the bifurcation of the pericallosal (PCA) and callosomarginal (CMA) arteries.1 Frontopolar artery (FPA) aneurysms are much less frequent, with a few cases reported in the literature.2 Changes in hemodynamic stress that potentiate aneurysm development are seen in relation to anatomical variations of cerebral arteries branching and radii.3 In the present case, the presence of the aneurysm was associated to an anatomical variation of the anterior cerebral artery complex, possibly contributing to the formation of an aneurysm in this infrequent location. Surgical treatment has been reported as the principal modality of treatment in these distal aneurysms. This article describes the first case of a saccular aneurysm originating from an anomalous FPA treated with endovascular coiling and discusses the difficulties regarding treatment of aneurysms in this unusual location.

Case report

A 55-year-old woman was admitted after experiencing acute loss of consciousness and tonic–clonic seizure at home. Her past medical history included hepatitis B infection, alcohol abuse and residual schizophrenia. There was no past history of hypertension, smoking, other drug abuse, SNC infection or trauma. On admission, the initial examination showed an unconscious patient (GCS 3) with reactive miotic pupils that diverged to the right (Hunt & Hess classification grade 5, World Federation of Neurosurgeons grade 5). After stabilization, a computerized tomographic (CT) scan was performed (Fig. 1) showing parasagital frontal subarachnoid hemorrhage and bilateral frontobasal intracerebral hematoma (ICH) opened to the ventricular system (Fisher III). Moderate dilatation of the ventricles also appeared as a sign of acute hydrocephalus. AngioCT scan detected an aneurysm arising from right FPA and signs of vasospasm in both ACAs. Before angiography was performed, an external ventricular drainage was placed. Angiography (Fig. 2A, C and E) revealed a saccular aneurysm of 5mm of diameter, with a neck of 3mm, at the origin of a right atypical FPA. The anatomical variation of right DACA consisted in FPA arising from the CMA trunk originated from the A2 segment. Right CMA seems to be larger than the PCA after their bifurcation. There was also an associated aneurysm at anterior communicating artery (AComA) of l.4mm of main diameter that did not show signs of recent bleeding. After selective microcatheteration of the FPA aneurysm, it was completely obliterated with 2 coils (Fig. 2B, D and F) maintaining the distal arterial lumen totally permeable. During her hospitalization a ventriculoperitoneal shunt was placed due to chronic hydrocephalus. Nowadays, the patient is at home and is orientated, able to keep a sensible conversation and walking.

Fig. 1.
(0.23MB).

Initial axial CT scan, demonstrating parasagital frontal subarachnoid hemorrhage and bilateral frontobasal intracerebral hematoma opened to the ventricular system with signs of acute hydrocephalus.

Fig. 2.
(0.48MB).

Anteroposterior (A), lateral (C) and detail (E) views of right carotid angiogram obtained before embolization showing an aneurysm in the right FPA. As a part of anterior cerebral artery complex variation, right FPA arises from the CMA trunk with origin in the A2 segment. Post-embolization right carotid angiogram, anteroposterior (B), lateral (D) and detail (F) views demonstrating a complete aneurysm obliteration and distal arterial lumen totally permeable.

Discussion

DACA aneurysms are very infrequent, comprising about 6% (range 2–9%) of all intracranial aneurysms in different series.1,4 Among DACA aneurysms, A3 segment aneurysms are the most frequent with an incidence of 69–82%, especially at the CMA–PCA junction.1 Much more infrequent, A2 segment aneurysms (A2A) have a reported incidence about 5–22% of all DACA aneurysms. They can appear at the main A2 trunk or on its frontobasal branches. Lehecka et al. found in their 35-A2A patients series that the most frequent location of A2A is on the A2 trunk at the origin of the FPA.1 Few FPA aneurysms have been reported and, up to our knowledge, only eight cases of aneurysms of the FPA, when it arises from CMA have been previously described.2

Although aneurysm pathogenesis is not completely understood, congenital variations in the circle of Willis can predispose to the formation of saccular aneurysms due to an increased in hemodynamic stress. Deviation from optimal geometrical parameters (radii, branch and bifurcation angles) creates areas of abnormal wall shear stress level that leads to endothelial injury and a wrong remodeling response that finally initiates aneurysm development.3 Consistently, a higher incidence of vascular variations in clinical series of patients harboring aneurysms in comparison with anatomic studies without aneurysms has been reported. Lehecka et al. in their angiographic analysis of patients with DACA aneurysms found that the most common vascular variation was bihemispheric ACA with an incidence of 15% followed by azygos ACA and triplication of ACA.1 The anatomical variations between FPA, CMA and PCA are rare. The most common DACA complex consists in OFA and FPA arising directly from A2 segment with CMA–PCA bifurcation located in A3 segment. Distribution of distal branches is less constant (Fig. 3A). FPA branching from CMA has been described in 9% of the hemispheres examined. In relation to vessel diameter, CMA can have greater diameter than PCA in 44% of cases, the PCA being larger in 23% and the FPA of greatest diameter in 9%. CMA and PCA have the same diameter in the rest 34% of cases.5 The anatomical variation of the case that we describe consists in a right CMA–PCA bifurcation located at A2 segment with a CMA trunk that gives origin to FPA, AIFA and middle internal frontal artery (MIFA) (Fig. 3B). CMA trunk seems to show a greater diameter than PCA. Here we report an infrequent aneurysm location and we suggest that it can be, at least, partially explained by the influence of the associated anatomical DACA vascular variation in the flow pattern.

Fig. 3.
(0.12MB).

Anatomic diagrams of vascular patterns of DACA. Most frequently described configuration (A) consists in FPA arising directly from A2 segment with CMA–PCA bifurcation located in A3 segment. PCA has greater diameter than CMA. Present case vascular variation (B) involves right CMA–PCA bifurcation located at A2 segment with a CMA trunk that gives origin to FPA, AIFA and MIFA. CMA showed greater diameter than PCA.

DACA aneurysms have some especial features that make their management difficult. These aneurysms can represent a surgical challenge due to their location deep inside the interhemispheric space, the presence of dense adhesions between the cingulated gyri, the possible difficulties in preserving major draining veins and the embedding of the aneurysm dome in surrounding brain tissue and their consequent tendency to rupture during surgical exposure. However, surgical treatment of DACA aneurysms shows similar outcome to other ruptured aneurysms in different locations.1 Endovascular treatment also entails difficulties due to their distal location, unfavorable neck-dome proportion and branches originating close to the base of these aneurysms. Nowadays, difficulties found during endovascular treatment of DACA aneurysms can be solved with the new suitable microcatheter, guidewires and coils, so similar results to the surgical option can be achieved.4 Therefore, patient and aneurysm characteristics should be take into account in order to choose the best treatment option in each case. As far as we know, all cases previously reported of FPA aneurysms associated with variations in DACA complex were treated by surgical clipping. In our case, the FPA aneurysm was successfully completely obliterated by coiling during the initial angiography and FPA lumen was kept totally permeable.

Conclusions

This report shows the importance of a cautious review of vascular studies in the case a vascular variation is found in order to exclude aneurysms in less common locations. When distal FPA aneurysm characteristics allow coil embolization, endovascular management can be considered a feasible and safe option.

References
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M. Lehecka,H. Lehto,M. Niemela,S. Juvela,R. Dashti,T. Koivisto
Distal anterior cerebral artery aneurysms: treatment and outcome analysis of 501 patients
[2]
F. Afshar
Direct surgical obliteration of frontopolar artery aneurysm
Surg Neurol, 15 (1981), pp. 135-136
[3]
A.M. Nixon,M. Gunel,B.E. Sumpio
The critical role of hemodynamics in the development of cerebral vascular disease
J Neurosurg, 112 (2010), pp. 1240-1253 http://dx.doi.org/10.3171/2009.10.JNS09759
[4]
T. Menovsky,W.J. van Rooij,M. Sluzewski,D. Wijnalda
Coiling of ruptured pericallosal artery aneurysms
Neurosurgery, 50 (2002), pp. 11-14
[5]
H.C. Ugur,G. Kahilogullari,A.F. Esmer,A. Comert,A.B. Odabasi,I. Tekdemir
A neurosurgical view of anatomical variations of the distal anterior cerebral artery: an anatomical study
J Neurosurg, 104 (2006), pp. 278-284 http://dx.doi.org/10.3171/jns.2006.104.2.278
Copyright © 2012. Sociedad Española de Neurocirugía
Neurocirugía (English edition)

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