Lifetime Effects of Small Unruptured Intracranial Aneurysms

BACKGROUND: Recent prospective multicenter studies have shown that the probability of rupture of unruptured aneurysms with maximal diameter <7 mm is rather low. However, the overall risks and long-term impact of unruptured aneurysms on lifetime quality of life are still unknown. METHODS: A mathematical model of the natural history of intracranial aneurysms was constructed, in which the hypothetical individuals with or without unruptured aneurysm transit between discrete health states. The annual rupture rate of small aneurysms was assumed to be 0.5% in the baseline analysis, followed by the subsequent sensitivity analysis. The analyses were continued until cumulative death rate from subarachnoid hemorrhage or other causes reached 1.0. - RESULTS: Age-specific ratios of death of subarachnoid hemorrhage in the individuals harboring unruptured aneurysm, if dying at 60 years old, were 25% in men and 43% in women. These ratios decreased rapidly with higher age. Most (more than 90%) patients with small aneurysms were expected to die of diseases other than subarachnoid hemorrhage. In the baseline analysis (60-year-old individuals), lifetime lost to small aneurysms could be estimated as 3.8% for men and 4.2% for women, but a somewhat larger impact could be identified in the young and/or female individuals compared with in the elderly and/or male individuals. CONCLUSIONS: Lifetime effects of small unruptured aneurysms without risk factors increasing the probability of rupture are relatively small, andmost patients were expected to die of diseases other than subarachnoid hemorrhage.