Microneurosurgical management of internal carotid artery bifurcation aneurysms

doi:10.1016/j.surneu.2009.01.028

Surgical Neurology

Volume 71, Issue 6, June 2009, Pages 649-667

https://doi.org/10.1016/j.surneu.2009.01.028 Get rights and content

Abstract

Background

Internal carotid artery bifurcation aneurysms form 2% to 9% of all IAs. They are more frequent in younger patients than other IAs. In this article, we review the practical microsurgical anatomy, the preoperative imaging, surgical planning, and the microneurosurgical steps in the dissection and the clipping of ICAbifAs.

Methods

This review and the whole series on IAs are 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 11 000 patients with IAs since 1951. In the Kuopio Cerebral Aneurysm Database of 3005 patients with 4253 IAs, 831 (28%) patients had altogether 980 ICA aneurysms, of whom 137 patients had 149 (4%) ICAbifAs. Ruptured ICAbifAs, found in 78 (52%) patients, with median size of 8 mm (range, 2-60 mm), were associated with ICH in 15 (19%) patients. Ten (7%) ICAbifAs were giant (≥25 mm). Multiple aneurysms were seen in 59 (43%) patients. The ICAbifAs represented 18% of all IAs ruptured before the age of 30 years.

Conclusions

The main difficulty in microneurosurgical management of ICAbifAs is to preserve flow in all the perforators surrounding or adherent to the aneurysm dome. This necessitates perfect surgical strategy based on preoperative knowledge of 3D angioarchitecture and proper orientation during the microsurgical dissection.

Introduction

We classify ICA aneurysms into 7 groups based on their site of origin, wall morphology, and clinical or surgical behavior: (a) ICAextraAs, (b) ICApetrAs and ICAcavAs, (c) ICAophtAs, (d) ICAwallAs and ICAmalignantAs, (e) ICA-PCoAAs, (f) ICA-AChAAs, and (g) ICAbifAs (Table 1).

Dott [11] was the first neurosurgeon to treat an ICA aneurysm by direct surgery, wrapping it with a piece of muscle in 1933. This was also the first surgical attempt to treat an IA [67]. Since that time, despite the advances in the field of microneurosurgery, aneurysms at this location have remained difficult to treat.

The ICAbifAs are located at the bifurcation of the ICA where it divides into the A1 segment of the ACA and the M1 segment of the MCA (Fig. 1). The ICA bifurcation is usually the highest point of the Circle of Willis. The apex of the ICA bifurcation, similar to the MCA bifurcation or the tip of the basilar artery, is under particular hemodynamic stress and high wall shear stress [45]. This apparently adds to the risk of saccular IA formation through pathological remodeling of the arterial wall of the branching site by impact, deflection, separation of CBF streamlines, and vortex formation at the lateral angles [45], [63]. The ICAbifAs tend to arise rather at the junction of the ICA and the A1 segment of the ACA than at the junction of the ICA and the M1 segment of the MCA [46], [65].

The ICAbifAs are unusual lesions. Their most striking feature is the younger age of patients at the time of rupture as compared to IAs at other locations [1], [21], [23]. The ICAbifAs may represent more than 40% of all IAs in patients younger than 20 years [23], [27], [28], [33], [51]. There is no clear explanation, but arterial wall deficits and wider angle of the ICA bifurcation may be risk factors.

The microneurosurgical exposure and clipping of ICAbifAs is demanding due to (a) high position with respect to the skull base, (b) attachment of the dome to the surrounding brain parenchyma, (c) large number of perforators surrounding the base and/or the dome, and (d) the relatively high risk of intraoperative rupture. The orientation of the aneurysm dome affects the clipping, with the posterior orientation being the most difficult. Precise dissection in the 3D anatomy of ICAbifAs and the surrounding perforators requires not only experience and microsurgical skill but also patience to work on the aneurysm base under repeated protection of temporary and pilot clips.

This review, and the whole series on IAs, is intended for neurosurgeons who are subspecializing in neurovascular surgery. The purpose is to review the practical anatomy, the preoperative planning, and the avoidance of complications in the microsurgical dissection and clipping of ICAbifAs.

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 Eastern Finland. These 2 centers have treated more than 10 000 patients with IAs since 1951 and more than 9000 patients during microsurgical era since mid 1970s. 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.

Section snippets

Occurrence of ICAbifAs

The ICAbifAs are reported to represent from 2% to 9% [5], [21], [35], [37], [46], [67], [79] of all IAs. Table 2, Table 3, Table 4, Table 5 present the clinical data on the 137 patients with ICAbifA in a 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, 831 (28%) had 980 ICA aneurysms (Table 2). There were 137 patients with 149 ICAbifAs, 4% of all the 4253 IAs and 15% of all the 980 ICA

Internal carotid artery

The microneurosurgical anatomy of the ICA and its branches has been earlier described by Yaşargil et al [84], [85], [86] and others [17], [20], [44], [57], [67] in detail.

Fischer divided the ICA into 5 different segments: (a) cervical, (b) petrous, (c) cavernous, (d) clinoid, and (e) supraclinoid [12]. Rhoton et al [59], [60] defined 4 segments: (a) cervical (C1), (b) petrous (C2), (c) cavernous (C3), and (d) supraclinoid (C4) [17] (Fig. 2).

The cervical ICA portion extends from the common

Imaging of ICAbifAs

Digital subtraction angiography is still the present “gold standard” in many centers. Multislice helical CTA is the primary modality for imaging of IAs in our centers for several reasons: (a) the virtual independence from the hemodynamic situation; (b) the noninvasive and quick imaging technique; (c) the comparable sensitivity and specificity to DSA in aneurysms larger than 2 mm [19], [30], [31], [68], [73], [80], [82], [83]; (d) the disclosure of calcifications in the walls of arteries and the

Microneurosurgical strategy with ICAbifAs

The ICAbifAs are challenging to approach because they are located at the highest point of the ICA, overlaid by the frontal lobe and surrounded by perforators. The surgical trajectory should provide optimal visualization of the whole ICA bifurcation and the ICAbifA with the least possible brain retraction. The aim of the microneurosurgical clipping is the total occlusion of the aneurysms sac with preservation of flow in the main branches and the perforating arteries surrounding the aneurysm

General principles

The close proximity of several perforator groups makes the dissection of the ICAbifA tedious in the narrow working channel in the proximal part of the sylvian fissure [9] (Fig. 4, Fig. 6). The aneurysm base with the adjacent arterial branches should be visualized before clipping. If the ICAbifA is obstructing the view toward the perforators hidden behind the dome, it may be necessary to first place a pilot clip at the aneurysm base and with that in place to continue dissection of the

Planning

The anteriorly or “forward” projecting ICAbifAs originate from the anterior aspect of the ICA bifurcation (Fig. 7A-D, see video ICAbifA—2 Hernesniemi). They are generally easier to visualize during dissection, and they are less involved with perforators than other ICAbifAs. The anteriorly projecting ICAbifAs are often embedded in the fronto-orbital gyrus, so even slight retraction and elevation of the frontal lobe can cause intraoperative rupture, for example, during subfrontal dissection

Associated aneurysms

The ICAbifAs are often associated with other IAs. In the Kuopio series, 43% of all ICAbifA patients and 26% of those with a ruptured ICAbifA had at least 1 additional IA (Table 5). Bilateral ICAbifAs were seen in only 6%. Our strategy is usually to clip all the IAs that can be exposed through the same craniotomy. It is advisable to clip the ruptured IA first, and if this succeeds without particular difficulties, additional IAs can be treated in the same session. We do not prefer to clip the

Giant ICAbifAs

Giant ICAbifAs comprised 7% of all ICAbifAs in the Kuopio series. The dome of a giant ICAbifA is usually at least partially covered by the frontal lobe and extends also into the sylvian fissure. Giant ICAbifAs often involve the origins of the A1 and the M1. Perforating arteries frequently follow and/or arise from the base region of these IAs, and it may be very difficult, even impossible, to dissect them free. The large size, distorted anatomy, origins of the perforating arteries and other

Fusiform ICAbifAs

Fusiform ICAbifAs are extremely rare, only 1 of 3005 patients in the Kuopio series (Table 2). They lack a definable neck, which could be clipped while preserving the afferent or efferent arteries (see video ICAbifA—6 Hernesniemi ). The parent artery is either circumferentially involved in the aneurysmal dilatation or it ends in a large thrombosed sac, and its distal branches arise from the base of the sac [79]. Wrapping, trapping, excision, and bypass surgery can be considered [64].

Acknowledgment

We thank Mr Ville Kärpijoki for excellent technical assistance.

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^☆: Conflict of interest statement: The authors declare to have no conflict of interest.

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TechniqueMicroneurosurgical management of internal carotid artery bifurcation aneurysms☆

Abstract

Background

Methods

Results

Conclusions

Introduction

Section snippets

Occurrence of ICAbifAs

Internal carotid artery

Imaging of ICAbifAs

Microneurosurgical strategy with ICAbifAs

General principles

Planning

Associated aneurysms

Giant ICAbifAs

Fusiform ICAbifAs

Acknowledgment

Surg Neurol

Surg Neurol

Surg Neurol

Surg Neurol

Surg Neurol

Surg Neurol

Clin Neurol Neurosurg

Eur J Radiol

Surg Neurol

Surg Neurol

Surg Neurol

Clin Neurol Neurosurg

Surg Neurol

Surg Neurol

Surg Neurol

Eur J Radiol

Am J Otolaryngol

Surg Neurol

Clin Radiol

Cerebral artery aneurysms in infancy, childhood and adolescence

Childs Brain

Anomalies of the posterior communicating artery and their potential clinical significance

J Neurosurg

Dysgenesis of the internal carotid artery associated with transsphenoidal encephalocele: a neural crest syndrome?

AJNR Am J Neuroradiol

The anterior choroidal artery; its origins course, distribution, and variations

AMA Arch Neurol Psychiatry

Direct microsurgical approach to aneurysms of the internal carotid bifurcation

Surg Neurol

Unilateral dysgenesis of the internal carotid artery: spectrum of imaging findings

Can Assoc Radiol J

Intracranial aneurysms: cerebral arterio-radiography: surgical treatment

Edinb Med J

Die Lageabweichungen der vorderen Hirnarterie im Gefassbild

Zentralbl Neurochir

CTA of the ICA bifurcation and intracranial vessels

Eur Radiol

Techniques of aneurysm surgery. III: internal carotid artery aneurysms

Remodeling of saccular cerebral artery aneurysm wall is associated with rupture: histological analysis of 24 unruptured and 42 ruptured cases

Stroke

Microsurgical anatomy of the arteries of the pituitary stalk and gland as viewed from above

Acta Neurochir (Wien)

Microsurgical anatomy of the supraclinoid portion of the internal carotid artery

J Neurosurg

Congenital absence of the internal carotid artery: case reports and review of the collateral circulation

AJNR Am J Neuroradiol

Microsurgical management of cerebral aneurysms based in CT angiography with three-dimensional reconstruction (3D-CTA) and without preoperative cerebral angiography

Acta Neurochir (Wien)

Microsurgical anatomy of the proximal middle cerebral artery and the internal carotid artery bifurcation

Neurosurgery

Internal carotid artery bifurcation aneurysms: surgical experience

Neurol Med Chir (Tokyo)

Ruptured intracranial arterial aneurysms of children and adolescents. Surgical and total management results

Childs Nerv Syst

Microneurosurgical management of anterior communicating artery aneurysms

Surg Neurol

Lateral supraorbital approach as an alternative to the classical pterional approach

Acta Neurochir Suppl

Subarachnoid hemorrhage in childhood and adolescence

J Neurosurg

Intracranial aneurysms in the pediatric population: case series and literature review

Surg Neurol

Technique
Microneurosurgical management of internal carotid artery bifurcation aneurysms☆