Endovascular strategy for unruptured cerebral aneurysms

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Abstract

The treatment of unruptured intracranial aneurysms (UIAs) remains complex and not clearly defined. While for ruptured intracranial aneurysms the management and the treatment option (surgery or endovascular treatment) are well defined by several trials, for asymptomatic UIAs the best management is still currently uncertain. The rationale to treat an UIA is to prevent the rupture and its consequent SAH and all complications derived from hemorrhage or reduce/eliminate neurological palsy. Although this statement is correct, the indication to treat an UIA should be based on a correct balance between the natural history of UIA and treatment risk. Patient's clinical history, aneurysm characteristics, and strategy management influence the natural history of UIAs and treatment outcomes. In the last 10 years and more, two important large multicenter studies were performed in order to analysis of all these factors and to evaluate the best treatment option for UIAs. The aim of this paper is to try to synthesize the possible indications to the endovascular treatment (EVT), when and how to treat an UIA.

Introduction

The treatment of unruptured intracranial aneurysms (UIAs) remains complex and not clearly defined. While for ruptured intracranial aneurysms the management and the treatment option (surgery or endovascular treatment) are well defined by several trials [1], [2]; for asymptomatic UIAs the best management is still currently uncertain.

The prevalence of UIAs is estimated at 2–4% of the adult population with an incidence of subarachnoid hemorrhage (SAH) due to their rupture at 10/100,000/year [3]. High morbidity and mortality (45–75%) rate due to SAH are very well known and described, despite the current technique of treatment and reanimation assistance [4].

Despite the fact generally intracranial aneurisms are asymptomatics up to their rupture, they can have an unspecific symptom as frequent headache resistant to medical treatment or they can be disclosed by nerve palsy or compression effect to nervous structures.

Thanks to the great development of mini-invasive imaging techniques in the last 20 years with CTA or MRA, the incidence of “incidental finding” of asymptomatic UIAs are frequent and increasing, making hard, complex and controversial the decision about the indication to the treatment.

The rationale to treat an UIA is to prevent the rupture and its consequent SAH and all complications derived from hemorrhage and to reduce or eliminate nerve palsy, if present. Although this statement is correct, the indication to treat a UIA should be based on a correct balance between the natural history of UIA and treatment risk (surgery or endovascular).

The natural history of UIAs and treatment outcomes are influenced by:

  • -

    Patient's clinical history, such as previous aneurysmal SAH, age, and coexisting medical conditions (collagenopathy and other genetic condition), alcohol-abuse, smoking;

  • -

    Aneurysm characteristics, such as size, location, and morphology;

  • -

    Strategy management, such as the experience of the surgical or endovascular team and the treating hospital.

In the last 10 years and more, two important large multicenter studies were performed in order to analysis of all these factors and to evaluate the best treatment option for UIAs [5], [6].

Although the criticisms and controversies derived from these studies, they represent the basis for the management of UIAs and they can be used to search the best indication treatment.

The aim of this paper is to try to synthesize the indication to endovascular treatment (EVT), when and how to treat an UIA.

Section snippets

Indications to treatment: when to treat an UIA?

When to treat an UIA? This is the real problem! Many factors can influence the choice and the type of treatment of UIAs according to ISUIA 1 and 2 studies:

  • (1)

    Patient clinical history, such as age, and coexisting medical conditions, alcohol-abuse, smoking, previous aneurysmal SAH;

  • (2)

    Aneurysm characteristics, such as size, location, morphology and its symptom;

  • (3)

    The hemodynamic environment;

  • (4)

    Factors in management, such as the experience of the surgical or endovascular team and the treating hospital.

All

Endovascular therapy and objectives, how to treat

The first historical attempts of endovascular treatment of unruptured intracranial aneurysms were performed after the introduction of detachable coils in 1991. A microcatheter was positioned within the aneurysmal sac and coils were released to provide a dense packing of coils to exclude the aneurysm from the intracranial circulation (Fig. 1).

Since late ‘90s the introduction of remodeling balloons and intracranial stents encouraged the development of the treatment of broad-based aneurysms that

Pharmacological aspects in intracranial stenting

According to cardiological protocols, a dual antiplatelet therapy is usually administered when a stent is placed intracranially. Patients treated with stent-assisted coiling or FDs receive a pre-treatment (at least 7–10 days before in our clinical experience) with Clopidogrel 75 mg/day or Ticlopidine 250 mg (2 tablets/day), ASA 300 mg/day and gastric protector 1 tablet/day (Lansoprazole in most cases) considering all known cross-reactions [21]. Platelet inhibition may be evaluated with in vitro

Recanalization aneurysm rate for the EVT

Aneurysm rest and recurrence are two important technical limits of EVT.

The magnitude and clinical significance of these drawbacks are now well-known and embolized-patients need to have a longer follow-up compared to clipped patients [22].

Patients with ruptured aneurysm have a higher incidence of recurrence rate compared to patients affected by unruptured aneurysm. Nguyen et al. found a recanalization rate of 53.5% in the ruptured aneurysms versus 22.5% for unruptured aneurysms (p = 0.001)

Conclusions

The life cycle of aneurysms is a complex process with multiple actors where the flow dynamics play a key role in the process. The treatment of UIAs remains complex and not clearly defined. The endovascular treatment may be considered a safe and effective approach of unruptured intracranial aneurysms, considering the technical developments that allow the complete occlusion of the aneurismal sac also in challenging situations, such as the bifurcational aneurysms. These encouraging results,

Conflict of interest

None.

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