Introduction: Newer natural history studies show anterior communicating artery aneurysms have a higher risk of rupture than was historically appreciated (1-3). Concurrent with a better understanding of aneurysm risk, the morbidity of surgical and endovascular treatment continues to decline to levels which suggest intervention even for small aneurysms (4). With declining treatment risk and better understanding of natural history, an aggressive treatment strategy may be warranted.
Methods: 149 patients with unruptured anterior communicating aneurysms were treated by the senior authors over a five-year period. Treatment was performed by operators trained in endovascular and surgical techniques. Modality of treatment was based on estimate of highest efficacy/lowest risk. Outcomes were recorded at three months and one year from treatment. The primary outcome measure was a modified Rankin scale (mRS) of >2 or persistent cognitive impairment as assessed by a neuropsychologist when indicated.
Results: Age averaged 61 years, range of 34-84 years. Median aneurysm size was 5.5 mm (IQR 4-7 mm). Sixty-eight percent of aneurysms were less than 7 mm. Clipping was performed in 98 patients (65.8%). Poor outcome was observed in 12 patients (8%). Neither aneurysm size nor treatment method were predictive of poor outcome. Both a history CAD/MI and older age were most significantly associated with poor outcome (CAD/MI OR=8.11, 95% CI 2.20-29.86, p=0.002; Age OR=1.09, 95%CI 1.019-1.17, p=0.013). When dichotomized for age >65 years, the odds of poor outcome increased nearly 11-fold (OR=10.93, 95% CI 2.29-52.03, p=0.003).
Conclusions: The risk of endovascular or surgical treatment of unruptured anterior communicating artery aneurysms for patients under age 65 is exceedingly low. Comparing treatment risk with natural history studies, patients treated under 65 years old can be expected to outperform natural history within five years. Recognizing the risk of smaller anterior communicating artery aneurysms, an aggressive management strategy is supported, particularly in younger patients.
Patient Care: Neurosurgeons considering treatment of smaller unruptured anterior communicating artery aneurysms would be able to make a more informed decision for treatment versus observation and have better data for patient counseling about the risks of these aneurysms, both treated or untreated.
Learning Objectives: By the conclusion of this session, participants should be able to 1) discuss newer natural history studies and the greater risk posed by anterior communicating artery aneurysms when compared to other anterior circulation aneurysms, 2) appreciate the overall trend in declining risk for aneurysm treatment and greater role of endovascular treatment of unruptured aneurysms, and 3) gain a better understanding of treatment risk for anterior communicating artery aneurysms in particular and risk factors for poor outcome.
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. doi:10.1056/NEJMoa1113260.
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. doi:10.1016/j.surneu.2006.06.025.
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.
4. O’Neill AH, Chandra RV, Lai LT. Safety and effectiveness of microsurgical clipping, endovascular coiling, and stent assisted coiling for unruptured anterior communicating artery aneurysms: a systematic analysis of observational studies. J NeuroInterventional Surg. September 2016:neurintsurg-2016-012629.