Relationship of A1 segment hypoplasia to anterior communicating artery aneurysm morphology and risk factors for aneurysm formation

J Neurosurg 127:89–95, 2017

Hypoplasia of the A1 segment of the anterior cerebral artery is frequently observed in patients with anterior communicating artery (ACoA) aneurysms. The effect of this anatomical variant on ACoA aneurysm morphology is not well understood.

METHODS Digital subtraction angiography images were reviewed for 204 patients presenting to the authors’ institution with either a ruptured or an unruptured ACoA aneurysm. The ratio of the width of the larger A1 segment to the smaller A1 segment was calculated. Patients with an A1 ratio greater than 2 were categorized as having A1 segment hypoplasia. The relationship of A1 segment hypoplasia to both patient and aneurysm characteristics was then assessed.

RESULTS 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).

CONCLUSIONS Our 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.

 

Endovascular Therapy of Very Small Aneurysms of the Anterior Communicating Artery: Five-fold Increased Incidence of Rupture

Neurosurgery 68:731–737, 2011 DOI: 10.1227/NEU.0b013e3182077373

Intraprocedural rupture is a dangerous complication of endovascular treatment. Small ruptured anterior communicating artery (ACoA) aneurysms and microaneurysms present a challenge for both surgical and endovascular therapies to achieve obliteration. An understanding of the complication rates of treating ruptured ACoA microaneurysms may help guide therapeutic options.

OBJECTIVE: To report the largest cohort of ACoA microaneurysms treated with endovascular therapy over the course of the past 10 years.

METHODS: We performed a retrospective review of 347 ACoA aneurysms treated in 347 patients at Cleveland Clinic and Emory University over a 10-year period. Patient demographics, aneurysmal rupture, size, use of balloon remodeling, patient outcomes, intraprocedural rupture, and rerupture were reviewed.

RESULTS: Rupture rates were examined by size for all patients and subgroups and dichotomized to evaluate for size ranges associated with increased rupture rates. The highest risk of rupture was noted in aneurysms less than 4 mm. Of 347 aneurysms, 74 (21%) were less than 4 mm. The intraprocedural rupture rate was 5% (18/347) for ACoA aneurysms of any size. There was an intraprocedural rupture rate of 2.9% (8/273) among ACoA aneurysms greater than 4 mm compared with 13.5% (10/74) in less than 4-mm aneurysms. Procedural rupture was a statistically significant predictor of modified Rankin score after adjusting for Hunt and Hess grades (HH).

CONCLUSION: ACoA aneurysms less than 4 mm have a 5-fold higher incidence of intraprocedural rerupture during coil embolization. Outcome is negatively affected by intraprocedural rerupture after adjusting for HH grade.