Introduction: Natural history studies indicate that anterior communicating artery aneurysms have a higher risk of rupture than other anterior circulation lesions (1,2,3). As surgical and endovascular treatment improves, morbidity may fall to levels which justify intervention even for small lesions. With low treatment risk and a more nuanced understanding of these lesions, a more aggressive treatment strategy is justified.

Methods: The records of 149 patients with unruptured aneurysms of the anterior communicating artery treated by the senior authors over a five-year period were reviewed. Treatment selection was based on age, aneurysm anatomy, and medical comorbidities by a team where operators performed both endovascular and surgical techniques. Outcomes were recorded at three months and one year from treatment. The primary outcome measure was defined as a modified Rankin scale score (mRS) of >2 or persistent cognitive impairment as assessed by a neuropsychologist.

Results: Age averaged 61 years, range 34-84 years. Sixty-four percent of patients were female. Aneurysm size averaged 6 mm, range 2-15 mm. Clipping was performed in 65.8% of patients. Older patients were more likely to be treated endovascularly (OR=2.55; 95% CI 1.26-5.14, p=0.0089). The primary outcome measure was met in 8% of cases. Age >60 was the most significant predictor of poor outcome with a nearly 13-fold increased risk for older patients (OR=12.9; 95% CI 1.62-102.9, p=0.016). Patients under 60 years had a risk of poor outcome of 0.67%. No patient under 60 had an mRS>1.

Conclusions: The risk of combined endovascular and surgical treatment of unruptured anterior communicating artery aneurysms for patients under age 60 is low. Comparing treatment risk with natural history studies, patients treated under age 60 can be expected to outperform natural history within one to two years. Recognizing the risk of smaller anterior communicating artery aneurysms, a more aggressive management strategy is supported, particularly in younger patients.

Patient Care: The risk of anterior communicating artery aneurysms as reported in newer natural history studies is higher than traditionally reported for anterior circulation aneurysms. Treatment morbidity continues to fall as a result of better surgical care, and the improvement in endovascular approaches. Updated outcomes data are critical for both patients and cerebrovascular neurosurgeons when making the decision for treatment or observation.

Learning Objectives: At the conclusion of this session, participants should be able to: 1)Describe the natural history of small unruptured anterior communicating artery aneurysms, and understand the risk is higher for these lesions than other anterior circulation aneurysms, 2) understand the overall risk of treatment of small unruptured aneurysms is low, particularly in those less than 60 years old, and 3) compare overall treatment risk with natural history to better assess indications for treatment as treatment risk falls.

References: 1. Morita A, Kirino T, Hashi K, et al. The natural course of unruptured cerebral aneurysms in a Japanese cohort. N Engl J Med. 2012;366(26):2474-2482. 2. Mira JMS, Costa FADO, Horta BL, Fabião OM. Risk of rupture in unruptured anterior communicating artery aneurysms: meta-analysis of natural history studies. Surg Neurol. 2006;66:S12-S19 3. Weir B, Disney L, Karrison T. Sizes of ruptured and unruptured aneurysms in relation to their sites and the ages of patients. J Neurosurg. 2002;96(1):64–70.