Saccular aneurysms are most common in the anterior communicating artery (ACoA).
Frequently it is a wide necked aneurysm with an irregular shape, incorporate parent vessels, and are associated with significant variations in vascular anatomy.
The most common site of rupture of very small intracranial aneurysms was the anterior communicating artery (ACoA). Rupture of small and very small aneurysms is unpredictable, and treatment may be considered in selected high-risk patients according to factors such as young age, ACoA location, and hypertension 4).
Morphological Scoring System of Choi
According to 2D-DSA, the points of aneurysm are divided into 5 types 5) 6).
Chen et al., classified as Type I, II (IIa, IIb), III and IV, based on the various projections and size of aneurysm. The principle for the choice of operative side was designed based on the type of aneurysm and the A2 fork orientation (the interrelations between the plane of bilateral A2, AComA, and mid-saggital plane) 7).
Small aneurysms located at the anterior communicating artery carry significant procedural challenges due to a complex anatomy.
Inferior or downward direction
Posterior or backward direction
Suprachiasmatic pressure may cause altitudinal visual field deficits, abulia or akinetic mutism, amnestic syndromes, or hypothalamic dysfunction.
Neurologic deficits in aneurysmal rupture may reflect intraventricular hemorrhage (79%), brain hemorrhage (63%), acute hydrocephalus (25%), or frontal lobe signs (20%).
Giant AComA aneurysms are extremely rare and may present with vision loss 11).
Visual apparatus compression can occur from giant AComA aneurysm directed posteriorly and inferiorly 12).
The pattern of visual loss in these cases is variable. The common pattern of visual loss is bilateral field deficits.
The other patterns of visual loss due to AComA aneurysms are central scotoma, bilateral heteronymous deficits, monocular or binocular inferior field loss, asymmetrical bitemporal hemianopsia, and incongruous homonymous hemianopsia 13).
For CT classification see the Modified Fisher scale.
Of 204 patients that presented with an ACoA aneurysm, 34 (16.7%) were found to have a hypoplastic A1. Patients with A1 segment hypoplasia were less likely to have a history of smoking (44.1% vs 62.9%, p = 0.0410). ACoA aneurysms occurring in the setting of a hypoplastic A1 were also found to have a larger maximum diameter (mean 7.7 vs 6.0 mm, p = 0.0084). When considered as a continuous variable, increasing A1 ratio was associated with decreasing aneurysm dome-to-neck ratio (p = 0.0289). There was no significant difference in the prevalence of A1 segment hypoplasia between ruptured and unruptured aneurysms (18.9% vs 10.7%; p = 0.1605).
The results suggest that a hypoplastic A1 may affect the morphology of ACoA aneurysms. In addition, the relative lack of traditional risk factors for aneurysm formation in patients with A1 segment hypoplasia argues for the importance of hemodynamic factors in the formation of ACoA aneurysms in this anatomical setting 17).
Between January 2008 and May 2016, information on 179 consecutive patients with unruptured AcoA aneurysms was obtained and included demographic data, aneurysm features, risk factors for formation and rupture, treatment type, complications, and follow-up information. A 2-tailed t test was used for continuous data and the chi-square test for categorical variables. Statistical significance was set at P value < 0.05.
There were 76 patients 65 and older (42.5%) and 103 younger than 65 (57.5%). Conservative management was more common in older patients (67.1% vs 41.7%, P=0.001). Endovascular treatment was more commonly used in the older population (80% vs 61% of the treated aneurysms in older and younger group, P=0.16). Treatment-related complications were 8% but resulted in permanent neurological deficits in one patient (1.2%). Among conservatively treated aneurysms, three (3.2%) ruptured at follow-up resulting in patient death in two cases (2.4%). All three ruptures occurred in elderly patients.
With a modern approach that emphasizes endovascular therapy, especially in older individuals, unruptured AcoA aneurysms can be treated with a very low morbidity. Among patients with small aneurysms for which treatment was not deemed indicated or necessary, the rate of rupture at follow-up was not negligible, with 5.8% of older patients experiencing bleeding from the aneurysm 18).
Colby et al., retrospectively reviewed an IRB-approved database of patients with an aneurysm at a single institution for patients with ACoA or A1-A2 aneurysms treated with PED. Data analyzed included demographics, aneurysm characteristics, procedural details, follow-up results, and outcomes.
A total of 50 procedures were performed on 41 patients, including seven patients who underwent bilateral ‘H-pipe’ PED placement. The average age was 56 years and 46% of the patients were female. The average aneurysm size was 4.5 mm, and two large (>10 mm) aneurysms were treated. The vessel of origin was either the ACoA (26 aneurysms, 63%) or the A1-A2 junction (15 aneurysms, 37%). Eighteen patients (44%) had prior subarachnoid hemorrhage and 20 had previously been treated either with clipping (6 aneurysms, 15%) or coiling (14 aneurysms, 34%). Procedural success was achieved in 48/50 cases (96%) and two cases were aborted. Coils were deployed adjunctively in two cases (4%). Procedural outcomes included no deaths, one major ischemic stroke (2%), and two patients with intracranial hemorrhage (4%). Complete aneurysm occlusion was achieved in 81% of patients at 6 months and 85% of patients at last follow-up digital subtraction angiography.
The PED can be used safely and effectively in the treatment of aneurysms of the ACoA region. This represents a good alternative treatment option to microsurgical clipping and endovascular coiling 19).
A total of 20 patients with ruptured very small (<3 mm) anterior communicating artery aneurysms were consecutively treated with coil embolization. The average maximum diameter was 2.66 ± 0.41 mm. Complete aneurysm occlusion was achieved for 17 (85%) aneurysms and near-complete aneurysm occlusion for 3 (15%) aneurysms. Intraoperative perforation was seen in 2 (10%) patients without any clinical worsening or need for an external ventricular drain. A thromboembolic event occurred in 1 (5 %) patient without clinical worsening or radiologic infarct. Median clinical follow-up was 12 (±14.1) months and median imaging follow-up was 12 (±18.4) months.
This report describes the largest series of consecutive endovascular treatments of ruptured very small anterior communicating artery aneurysms. These findings suggest that coil embolization of very small aneurysms in this location can be performed with acceptable rates of complications and recanalization 20).
Between January 2008 and February 2015, 254 consecutive patients with 255 ACoA aneurysms were treated with coiling. We retrospectively reviewed intraoperative angiograms and medical records to identify intraprocedural rupture and thrombus formation, and re-measured aneurysm morphologies using CT angiography images. Multivariate logistic regression models were used to determine independent predictors of intraprocedural rupture and thrombus formation.
Of the 231 patients included, intraprocedural rupture occurred in 10 (4.3%) patients, and thrombus formation occurred in 15 (6.5%) patients. Patients with smaller aneurysms more often experienced intraprocedural rupture than those with larger aneurysms (3.5±1.3 mm vs 5.7±2.3 mm). Multivariate analysis showed that smaller ruptured aneurysms (p=0.003) were independently associated with intraprocedural rupture. The threshold of aneurysm size separating rupture and non-rupture groups was 3.5 mm. Multivariate analysis showed that a history of hypertension (p=0.033), aneurysm neck size (p=0.004), and parent vessel angle (p=0.023) were independent predictors of thrombus formation. The threshold of parent vessel angle separating thrombus and non-thrombus groups was 60.0°.
Ruptured aneurysms <3.5 mm were associated with an increased risk of intraprocedural rupture, and parent vessel angle <60.0°, wider-neck aneurysms, and a history of hypertension were associated with increased risk of thrombus formation during coiling of ruptured ACoA aneurysms21).
Anterior communicating artery aneurysm can cause visual symptoms by compressing the optic nerve or direct rupture to the optic nerve with focal hematoma formation. Park et al., emphasize that cerebral vascular study is highly recommended to detect intracranial aneurysm before its rupture in the case of normal CT findings with visual symptoms and frequent headache 22).
The direction in which the fundus projects was chosen as the morphological criterion between endovascular and surgical methods. The authors propose that microsurgical clip application should be the preferred option in the treatment of ACoA aneurysms with anteriorly directed fundi and that endovascular packing be selected for those lesions with posteriorly directed fundi, depending on morphological criteria 23).
A 69-year-old male without a past history of mental disorders and neurological symptoms presented with a 2-month history of anxiety, sadness, lack of pleasure in usual activities, fatigue, difficulties falling asleep and waking up early in the morning, reduced appetite, and weight loss. The patient was diagnosed with major depressive disorder and antidepressant treatment was initiated. Subsequent non-contrast computed tomography (CT) of the head demonstrated hypointense oval-shaped lesion within the projection of the anterior communicating artery. CT angiography confirmed the diagnosis of a 0.8 × 0.6 cm saccular aneurysm originating from the anterior communicating artery and anterior cerebral artery. The patient underwent microsurgical clipping of the aneurysm. On psychiatric assessment 1 month after the surgery, there were no signs of depressive disorder and antidepressive treatment was discontinued. On follow-up visit 1 year after the surgery, the patient did not have any mood symptoms.
The case indicates that organic brain lesions, including intracranial aneurysms, should be suspected in elderly patients presenting with their first episode of mental disorder 25).
A 55-year-old man presented with a 3-year history of visual impairment associated with personality changes. His sister had died after an intracerebral aneurysmal rupture. An examination revealed poor visual acuity in the right eye with a field defect, as well as impaired neurocognition. Computed tomographic (CT) angiography (Panel A) and magnetic resonance imaging of the brain revealed a partially thrombosed, calcified, 7-cm aneurysm of the anterior communicating artery, with surrounding edema (Panel B). Thrombectomy and aneurysmal repair were performed to reduce the risk of aneurysmal rupture and to alleviate the mass effect. The patient recovered from surgery and had improvement in his neurocognitive deficits and vision, and he was able to return to work. His condition remained stable 2 years later, and delayed CT showed collapse of the aneurysmal sac (Panel C). Giant aneurysms (>2.5 cm) represent a small proportion of brain aneurysms but are associated with a high rupture rate when left untreated. Approximately 20% of patients with a brain aneurysm have a first-degree relative with a brain aneurysm 27).