Unruptured Giant Intracerebral Aneurysms: Serious Trouble Requiring Serious Treatment – Case Report and Literature Review

Abstract

Giant intracranial aneurysms (ICGA) represent 3 to 5% of all intracranial aneurysms in adults. They are defined as arterial dilatations, with more than 25 mm in diameter. Despite important advances in the research of endovascular techniques of treating giant intracranial aneurysms, the management of these vascular malformations still poses great difficulties for neurologists and interventional radiologists. In particular, these challenges arise from the difficult and modified cerebral anatomy of patients with ICGA. Choosing the best treatment for patients with ICGA involves not only finding the perfect balance between the potential risks and benefits of endovascular treatment, but also taking into consideration the patient’s biological condition and associated diseases.

The aim of this paper is to describe the decisional algorithm of treating patients with giant intracranial aneurysms and factors which could influence the choice of endovascular technique.

We report a clinical case of a 63-year-old female with cardio-vascular risk factors (atrial fibrillation, high blood pressure), diagnosed with a symptomatic giant aneurysm of the right internal carotid artery and multiple cerebral micro-bleeds. Given the very large size of the aneurysm, its characteristics as well as patient’s associated comorbidities, it was decided to exclude the ICA aneurysm from circulation by occluding the parent vessel (right internal carotid artery) by using endovascular techniques.

Also, a review of the literature on the currently available endovascular methods for treating patients with giant intracranial aneurysms was performed in order to see the indications and possible long-term complications of each method.

In selected cases, the risks of serious complications associated with occluding a large cervical-cerebral vessel (as the internal carotid artery) are far exceeded by the risk for rupture of giant aneurysms, which is fatal in many cases. Nevertheless, it is of utmost importance to mention that, although the use of endovascular methods leads to a significant increase in life expectancy, a severe decline in quality of life might be experienced by these patients.

Keywords:unruptured giant cerebral aneurysm, interventional neuro-radiology, occlusion of internal carotid artery (ICA), review of the literature, cerebral microhaemorrhages.

INTRODUCTION

Definition, pathophysiology and clinical aspects of giant intracranial aneurysms

As stated above, giant intracranial aneurysms (ICGA) are vascular malformations with more than 25 mm in diameter (1), which are more often found in females than males (2:1 ratio). Their overall risk of rupture depends on both patient’s characteristics (age, comorbidities, and population appurtenance) and features of the aneurysm (size and location, history of cerebral hemorrhage from other aneurysms). Out of all non-traumatic subarachnoid hemorrhages (SAH), 85% are caused by the rupture of an intracranial aneurysm (2). For ICGA, the lowest five-year risk of rupture calculated with using the PHASES score is 5.3%, but this risk can reach almost 20% in special cases (3). Despite significant advances in neurocritical care and management of patients with SAH, mortality associated with the rupture of ICGA still remains very high. Thus, mortality at two years following the rupture of a ICGA ranges from 80 to 100% (4). More often, ICGA become symptomatic due to their mass effect on the adjacent cerebral structures.

Most giant carotid artery aneurysms arise in key vascular regions exposed to high hemodynamic stress, due to a combination of pathogenic factors: endothelial dysfunction, turbulent blood flow, recurrent damage followed by healing (scarring) of the aneurysm wall (favoring the expansion of the aneurism and also intra-luminal thrombus formation), atherosclerotic degeneration of the arterial wall, media necrosis of the arterial wall, etc (5).

Giant aneurysms (GA) can be classified into saccular, fusiform and serpentine aneurysms, according to their appearance and pathogenesis (5). Saccular GA are round or oval vascular malformations, with a neck that connects them to the vessel. They are thought to arise from small saccular (berry) aneurysms through repeated tearing and scaring of the aneurysmal wall. These processes lead to an intra-aneurysmal turbulent flow, which maintains the progressive growth of the aneurysm. In contrast to saccular aneurysms, fusiform and serpentine aneurysms have no demonstrable necks attaching them to the vessel; they are usually elongated vascular malformations and generally develop by atherosclerotic degeneration of the arterial wall. The processes following the initial injury to the arterial wall are similar to those occurring in saccular aneurysms. The main difference between fusiform and serpentine aneurysms is that serpentine aneurysms have a tortuous and irregular lumen and usually derive from thrombosed fusiform aneurysms which recanalise (5).

Partially or complete thrombosed aneurysms are thought to appear due to inflammatory mechanisms triggered by chronic dissections and hematomas of the aneurysmal wall and by the concomitant proliferation of the vasa vasorum (6).

There are several diseases and predisposing factors associated with intracranial aneurysms. Patients with GA or multiple intracranial aneurysms should be screened for connective tissue disorders (Ehlers-Danlos syndrome, pseudoxanthomaelasticum) (7, 8), autosomal dominant polycystic kidney disease (approximately 11% of patients with ADPKD have unruptured intracranial aneurysms) (9), Moyamoya syndrome (giant aneurysms are very rare in these cases), familial aneurysms (the prevalence of aneurysms in relatives of patients with ICGA varies between 9 and 20% among different studies) (10, 11), etc. Moreover, cigarette smoking, hypertension and alcohol consumption are well-known factors that favor aneurysm formation, growth and rupture (12-14).

Carotid artery aneurysms can become symptomatic in three different ways: by rupture, (and so, causing subarachnoid hemorrhage), by acting as a tumor which exerts a mass effect on the adjacent cerebral structures, and by compressing an adjacent vessel, thus determining cerebral ischemic lesions. Symptoms vary depending on the localization and size of the aneurysm.

Given the high risk of rupture and invalidating symptoms associated with ICGA, patients who were identified with such vascular malformations are usually treated by neurosurgical or endovascular techniques. Due to difficult neurosurgical approaches, endovascular treatment is becoming the preferred method of treating giant aneurysms of the ICA.

Current strategies for treating giant intracranial aneurysms

Rational endovascular treatment decision-making in cases of ICGA requires taking into consideration the localization of the aneurysm, its anatomy and geometry, the size of neck and dometo- neck ratio, the presence of intra-aneurysmal thrombus, patient’s comorbidities, and last but not the least, the availability of endovascular materials needed for treatment. The current modern endovascular methods used for treating ICGA are summarized in Table 1.

CASE REPORT

A 63-year old female presented to the neurology department for right eye scotomas and perioral paraesthesias, which started two weeks before hospital admission. The patient was a chronic smoker (five pack-years) and was known to have vulgar psoriasis, atrial fibrillation, stage 2 hypertension, dyslipidemia, hypothyroidism and history of multinodular goiter treated with radioactive iodine (seven years prior to hospitalization in the neurology unit). She was on several antihypertensive drugs, antiarrhythmic drugs (propafenone), synthetic thyroid hormone replacement therapy and statins.

Clinical examination revealed left homonymous hemianopia and global brisk deep tendon reflexes.

Routine blood tests were normal, except for inflammation markers (elevated C-reactive protein and erythrocyte sedimentation rate) and increased low-density lipoprotein.

Cerebral magnetic resonance imaging (MRI) was performed (Fig. 1), which revealed a partially thrombosed giant saccular cerebral aneurysm with maximal diameters of 25/21 mm, and a 4 mm wide insertional neck and exerting a significant mass effect on the optic chiasm and on the third branch of the right trigeminal nerve. The origin of the GA was difficult to distinguish on the MRI exam. Furthermore, several highintensity lesions were noticed on the T2 and FLAIR sequences in both cerebral hemispheres (suggesting multiple microinfarctions) and also multiple low-signal blooming artifact microlesions on the T2* and gradient-echo sequence, suggesting microbleeds in bilateral lenticular nucleus and internal capsule, bilateral cerebellar hemispheres, and in the bilateral subcortical frontal, parietal and occipital white matter.

A “4 vessel” cerebral digital subtraction angiography (DSA) was performed, which confirmed the presence of an unruptured giant aneurysm situated in the communicant (C7) segment of the right internal carotid artery (Fig. 2). The patient was treated by endovascular techniques consisting of percutaneous embolization of the aneurysm, using 19 platinum coils. The presence of micro-bleeds, along with the fact that the patient had also atrial fibrillation (requiring permanent anticoagulant therapy) excluded the flow-diverter device option (that would have required long term double antiplatelet therapy). Nevertheless, in other cases, flow-diverter devices with or without concomitant coiling would have been a good choice for this type of aneurysm.

After six months, the patient presented to the hospital for reevaluation. She reported urinary incontinence, frequent falls, attention deficit and short-term memory impairment. The six-month follow-up cerebral MRI showed 50% reperfusion of the aneurysm, the ICA-GA increasing in size and exerting mass effect on the right cerebral peduncle. Moreover, the number of cerebral microbleeds was also increased.

Due to its characteristics, positioning and evolution, parent artery occlusion (right ICA) was performed in order to exclude the aneurysm from the cerebral circulation and to reverse the mass effect the aneurysm was exerting by eliminating the pulse pressure. The procedure was preceded by an occlusion balloon test, which was negative (the patient was clinically asymptomatic during the 20 minute-period in which a balloon was inflated, occluding the right ICA) (Fig. 3). Two coils were placed in the lumen of the right ICA.

At 12 hours post-ICA occlusion, the patient presented left hemiparesis and aphasia. A cerebral perfusion MRI was performed, which showed a decrease of cerebral perfusion in the territory of right ICA (Fig. 4). The cerebral CT scan at 48 hours revealed a right lenticular hypodensity. The patient received anticoagulant treatment, adequate hydration and systolic blood pressure was maintained between 140-160 mm Hg. The symptomatology progressively improved in the first 48 hours from onset.

After two years from the initial neurologic evaluation, the patient came to our hospital for periodical check-up. She did not report any new symptoms, but her caregivers mentioned severe progressive cognitive deterioration during the past year and significant changes in behavior and dietary preferences.

Clinical exam revealed right homonymous hemianopia, brisk deep tendon reflexes in the left limbs; Babinski sign was present in the right foot. In addition, the patient was bradikinetic and bradiphrenic and had a disinhibited behavior (she made offensive remarks, also considering her room colleagues inferior and asking them to feed her and make her daily hygiene, even though she had the ability to perform those tasks by herself), repeated the same information several times without remembering doing so and misplaced her personal objects. Neuro-cognitive evaluation revealed severe deterioration of several cognitive domains: episodic memory, attention and severe visual-spatial disorientation. A cerebral MRI was repeated and revealed a thrombosed aneurysm with 25 mm in the biggest diameter (stationary compared to the first measurements), which was exerting mass effect on the adjacent cerebral parenchyma and on the right half of the brainstem, associating important cerebral edema (Fig. 5).

The patient was treated with hyperosmolar solution intravenous perfusion for three days and received a short course of steroids.

DISCUSSION AND CONCLUSONS

Despite the numerous endovascular options from which the clinician has to choose when treating a patient with giant intracranial aneurysm, options are actually limited in cases of patients with severe comorbidities.

In the above-described case, the patient had a symptomatic ICGA, which obviously needed to be treated. The most suitable treatment for this type of malformation, considering its geometry, localization and dome-to-neck ratio, would have probably been placing a flow-diverter stent in the communicant segment of the right internal carotid, along with the embolization of the aneurysm with coils. Given the fact that the patient also had atrial fibrillation, which required permanent anticoagulant therapy, the placement of a flow-diverter stent became unadvisable, as she would have needed long term antiplatelet therapy in order to avoid acute thrombosis of the stent. Given the presence of the numerous cerebral microbleeds, the association of anticoagulant with double antiplatelet therapy would have made the risk of intracerebral hemorrhage much higher than the benefits of treatment.

In selected cases (aneurysms with particular anatomy that makes them surgically unapproachable, giant fusiform, saccular and serpentine aneurysms that are not suitable for other endovascular methods described above, or – as in our case – aneurysms treated by endovascular techniques, recanalised and unfitted for further endovascular approaches), occluding the parent vessel is a well-established and effective alternative treatment. By occluding the parent vessel, the GA is excluded from cerebral circulation and it is expected that the aneurysm will shrink due to the organisation and retraction of the clot, thus reversing or improving the mass effect which is exerted by the giant aneurysm.

There are two major complications associated with parent artery occlusion: ischemic complications (most frequently due to retrograde arterial thrombosis, or arterio-arterial distal embolism) and very rare hemorrhagic peri-procedural complications (by tearing the arterial wall) (16).

This case emphasizes the importance of periodical monitoring of patients subjected to parent artery occlusion for giant aneurysms in order to ensure proper management of complications that can occur. In our case, given the fact that the patient was on permanent treatment with anticoagulants, the intra-aneurysmal blood clot had not organized completely and continued to have a considerable weight and volume, thus still exerting a significant mass effect.

Conflict of interests: none declared

Financial support: none declared.

TABLE 1.

Endovascular methods of treating intracranial aneurysms (5, 4, 15)

FIGURE 1.

Cerebral MRI. Left – T2*, axial sequence: multiple microbleeds in both basal ganglia and internal capsules. Right – T2 axial sequence: round predominantly hypointense mass, exerting mass effect on adjacent structures (especially on the right cerebral peduncle)

FIGURE 2.

Left: cerebral “4 vessel” angiography – selective catheterization of the right internal carotid artery revealing an unruptured giant aneurysm situated in the communicant (C7) segment. Right: cerebral “4 vessel” angiography – post-embolization aspect

FIGURE 3.

Left: cerebral MRI. Left – T2: axial sequence – partially thrombosed GA of the right ICA. Left – T2*: axial sequence – partially thrombosed GA of the right ICA and multiple cerebral microbleeds

FIGURE 4.

Left: cerebral “4 vessel” angiography – post-ICA occlusion aspect; selective catheterization of the right common carotid artery revealing the absence of ICA filling. Right: selective catheterization of the left internal carotid artery revealing satisfactory filling of the right middle and anterior cerebral arteries

FIGURE 5.

Two-year check-up cerebral MRI. Up-left (T2 axial sequence) and up-right (FLAIR coronal sequence): thrombosed aneurysm exerting important mass effect on the adjacent structures. Down (T2* sequence): unruptured thrombosed GA of the left ICA and an increased number of cerebral microbleeds