PHASES and ELAPSS Scores Are Associated with Aneurysm Growth: A Study of 431 Unruptured Intracranial Aneurysms

Background: Understanding risk factors for intracranial aneurysm growth is important for patient management. We performed a retrospective study examining risk factors for the growth of unruptured intracranial aneurysms followed at our institution, evaluating both traditional risk factors and the PHASES (Population, Hypertension, Age, Size, Earlier Subarachnoid Hemorrhage, Site) score. Methods: We retrospectively reviewed a consecutive series of unruptured intracranial aneurysms followed at our institution for a minimum of 6 months over a 15-year period. The primary outcome of this study was aneurysm growth, defined as a ≥1-mm increase in maximum diameter. Risk factors studied included PHASES score, ELAPSS (Earlier Subarachnoid Hemorrhage, Location of Aneurysm, Age, Population, Size, and Shape) score, demographics, multiple aneurysms, previous subarachnoid hemorrhage, family history of aneurysm or subarachnoid hemorrhage, smoking, hypertension, and aneurysm shape, size, and location. The χ² test was used for comparison of categorical variables, and the Student t test was used for continuous variables. Results: The study cohort comprised 352 patients with a total of 431 unruptured intracranial aneurysms. The mean duration of follow-up was 4.8 years, and there was a total of 2100 aneurysm-years of follow-up. Forty aneurysms (9.3%) grew, for an annualized growth rate of 2.0% of aneurysms/year. Current smoking status was the sole modifiable risk factor associated with growth (growth rate of 5.1%/year compared with 1.5%/year for never smokers; P = 0.0004). Increasing size (odds ratio [OR], 1.22; 95% confidence interval [CI], 1.11–1.33; P < 0.0001), ELAPSS score (OR, 1.10; 95% CI, 1.09–1.11; P < 0.0001), and PHASES score (OR, 1.24; 95% CI, 1.20–1.28; P < 0.0001) were associated with growth as well. Age, location, previous subarachnoid hemorrhage, and hypertension were not independently associated with aneurysm growth. Conclusions: Our retrospective study suggests that aneurysm size, smoking status, PHASES score, and ELAPSS score are associated with aneurysm growth.