The authors of this study make the argument that for most small aneurysms in the anterior circulation, the predicted risk of rupture is much smaller than the risk of treatment complications, and therefore many of these small aneurysms are left untreated. However, a small proportion of these aneurysms do rupture and because these aneurysms by far outnumber other aneurysms, most instances of aneurysmal subarachnoid hemorrhage come from small aneurysms in the anterior circulation. Thus, the need for a better risk prediction model is required. The PHASES score is a model that provides absolute risks of rupture for aneurysms based on six easily retrievable factors which include population, hypertension, age, size of aneurysm, earlier SAH from another aneurysm, site of aneurysm. The score was utilized in this study to see if it is a predictor of aneurysm growth.
The authors analyzed a multicenter cohort of patients with unruptured intracranial aneurysms and follow-up imaging with computed tomography angiography or magnetic resonance angiography. They included 557 patients with 734 unruptured aneurysms. Eighty-nine (12%) aneurysms in 87 patients showed growth during a median follow-up of 2.7 patient-years (range 0.5-10.8). Using this cohort, they performed univariable and multivariable Cox regression analyses for the predictors of the PHASES score at baseline, with aneurysm growth as outcome. Per point increase in PHASES score hazard ratio (HR) for aneurysm growth was 1.32 (95% CI: 1.22-1.43). With the lowest quartile of the PHASES score (0-1) as reference, HRs for the second [PHASES 2-3] 1.07 (95% CI: 0.49-2.32), the third [PHASES 4] 2.29 (95% CI: 1.05-4.95), and the fourth quartile [PHASES 5-14] 2.85 (95% CI: 1.43-5.67).
It was concluded that this study shows that the PHASES risk score, which provides 5-year absolute risks of aneurysmal rupture, can also be used to identify aneurysms with a high relative risk of aneurysm growth. Despite the strengths of the study, while the PHASES score can be utilized as another surrogate marker for identification of aneurysms that have a higher risk of growth and also an aneurysms risk for rupture, it should be utilized with caution. This score will require further confirmation of its validity before it is implemented on a larger scale as aneurysms should not needlessly be treated give the risks and complications associated with the procedure.