**5. Evidence-based paradigms for treatment:**

GIAs can be secured effectively by neurosurgical or endovascular therapy, though there is a subset of factors (size, morphology, location, segment of artery, related anatomy, comorbidities as well as timing of surgery) which complicate treatment decision. Understanding the ability of variety techniques to the cerebrovascular team facilitates a comprehensive method for treating these lesions, maximizing efficacy and minimizing risk. In 2011 Fraser from Cornell University (New York) created a paradigm for approaching all aneurysms at the institution using currently accessible technology. We reported singlesurgeon's experience of ICA GIAs treatment. Based on literature (Fraser, 2011; Cantore, 2008; Kai, 2007, Sharma, 2008), American Society of Anaesthesiologists as well as senior author (PS) reflections, we propose the detailed model of treatment methods to decision making processes in GIAs, also indicating the possible alternatives. However, it should be pointed that a paradigm is a proposal referring to current technology in our institution.

374 Aneurysm

Abbreviations: DCI – delayed cerebral ischemia.

0

20

40

Sensitivity

60

80

100

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term outcome in ruptured ICA aneurysms.

quality-adjusted life-years (QALY) (Qureshi, 2007).

**5. Evidence-based paradigms for treatment:** 

a massive bleed assessed by the Fisher scale, postoperative neurological deficit occurrence and delayed cerebral ischemia were consecutively responsible for worse outcome (Fig.11).

Model

DCI

Hunt\_Hess\_scale Fisher scale

postoperative neurological deficit

**Figure 11.** Receiver operating characteristic curve (ROC curve) presenting consecutive factors (according to importance) responsible for combined postoperative mortality and unfavourable short-

Another important issue is how the cost-effectiveness of GIAs therapy compares with smaller aneurysms. The undoubted increased cost of GIA therapy in comparison with smaller aneurysms is related to more complex operative procedures, increased time of surgery and hospital stay. There is a lack of publications regarding such comparisons, however, the economic analysis of unruptured aneurysms proved that treatment is costeffective if addressed to large aneurysms and GIAs (Johnston & Gress, 1999). These lesions produce symptoms by compressing neural structures and have a high risk of rupture. Therefore a symptomatic patient harbouring unruptured GIA may potentially benefit more

GIAs can be secured effectively by neurosurgical or endovascular therapy, though there is a subset of factors (size, morphology, location, segment of artery, related anatomy, comorbidities as well as timing of surgery) which complicate treatment decision. Understanding the ability of variety techniques to the cerebrovascular team facilitates a comprehensive method for treating these lesions, maximizing efficacy and minimizing risk. In 2011 Fraser from Cornell University (New York) created a paradigm for approaching all aneurysms at the institution using currently accessible technology. We reported singlesurgeon's experience of ICA GIAs treatment. Based on literature (Fraser, 2011; Cantore, 2008; Kai, 2007, Sharma, 2008), American Society of Anaesthesiologists as well as senior

Abbreviations: ASA - American Society of Anaesthesiologists scale; BTO - balloon occlusion test; CTA - computer tomography angiography; HH - Hunt-Hess scale; ICH - intracranial haematoma; MRA - magnetic resonance angiography.

**Figure 12.** Treatment algorithm for GIAs evaluation and treatment in our institution.

Despite patient's previous radiograms, a meticulous preoperative diagnosis is to be complemented by means of cerebral rotational, three dimensional subtracted angiography (3D DSA) and computer tomography angiography (CTA) or optionally by magnetic resonance angiography (MRA). 3D DSA enables a visualisation of a detailed GIA's anatomical features and originating perforators, though its ability to demonstrate calcification or thrombosis is limited (Hoit, 2006). CTA accomplishes above limitations and moreover shows surrounding bony structures. In posterior fossa or ICA GIAs MRA can visualise adhering neural structures, although is performed occasionally in our institution. Conservative approach is preferred in individuals in fourth or fifth Hunt-Hess grade, excepting those with intracerebral haemorrhage. Conscious and informed patient's attitude to proposed GIA's treatment method is an important factor in making a decision. Endovascular therapy is approached to older individuals with high cardiopulmonary risk and when surgery is contraindicated. For ruptured GIAs an increased radiographic cerebral oedema may prevent direct clipping. Wide-necked GIAs not feasible for clipping should be secured by endovascular methods. GIAs originating at BA trunk or BA bifurcation with the neck located lower than normal are also offered endovascular treatment. A preferable group of patients for direct neck clipping are those younger than 65 years old. All GIAs amenable for clipping in neurosurgeon's opinion should be secured in this manner. In our institution distal PCA or ACA GIAs are excluded from a circulation by clipping technique. However, the most controversy refers to GIAs that are not suitable for both endovascular therapy and microsurgical clipping. In this case an endovascular therapy transforms these lesions into a chronic disease with a relapsing clinical course by further retreatments and repeated risk exposure (Sughrue, 2010). Flow-diverting stents potentially offer a meaningful benefit over surgery, although the outcome has not been sufficiently confirmed. Nonetheless, if endovascular therapy or direct clipping are not amenable bypass or parent artery sacrifice (trapping) is recommended, though bypass is not allowed in acute phase of SAH. Proper qualification to one of above surgical method is validated in balloon occlusion test (BTO). However this test is not meticulous enough, therefore the decision of treatment method can be supplemented by Xenon computer tomography or single-photon emission computed tomography (SPECT). Patients younger than 70 years old with equal or lower than grade II in American Society of Anaesthesiologists scale are qualifying for high-flow bypass without BTO, which is in accordance with contemporary literature (Cantore, 2008).

The contemporary experience with GIAs is limited to retrospective analysis of selected group of ICA GIAs (Szmuda & Sloniewski, 2011). Nonetheless, it demonstrates that experienced neurosurgeon (senior author - PS) can achieve excellent results using a single surgery, definitive and durable therapy.

#### **6. Conclusions/perspectives**

General unsatisfactory outcomes of GIAs do not warrant risky microsurgical or endovascular interventions. The more accustomed the neurovascular surgeon is the more difficult is the selection of the appropriate method for securing GIAs. However, in experienced hands the outcomes after treatment of giant and smaller aneurysms do not differ. In elderly populations, the efficacy must be weighed against the natural history of the GIA by considering expected remaining lifetime.

Endovascular embolization competes with open microsurgery in the field of cerebral aneurysms. Prospective and randomized trials (CURES, ATENA and STAT) are intent-totreat analyses, therefore not dedicated for GIAs. The promising outcomes achieved by endovascular therapy for small aneurysms nevertheless remain unconfirmed for GIAs. Application of these results to GIAs is misleading. To date, the knowledge is based on small published series.

Forced by the completion of both treatment options, continuous development of neither endovascular nor microsurgical methods is being observed. Hopefully for patient's benefit!
