SURGERY OF UNRUPTURED, ASYMPTOMATIC ANEURYSMS - A DECISION-ANALYSIS

Background: Asymptomatic cerebral aneurysms are diagnosed more frequen tly since the advent of computed tomography and magnetic resonance ima ging. Their management is currently empirical. We have used decision a nalysis to place it on a more analytical basis. Methods: Decision anal ysis was used to determine the benefit in years of survival free of se quelae resulting from elective surgery of unruptured aneurysms over na tural history. We took 2% as the annual rate of rupture (r), 73% as th e risk of death or disability with rupture (M), and 6.5% for the avera ge risk of elective surgery (S). Benefit was calculated from the equat ion L{[1-(1-r)L]M/2-S} [1] for life expectancy (L) corresponding to ea ch quinquennial age group from age 15 to 100 years. Sensitivity analys is was performed to take into account increasing risk of elective surg ery based on the size, and accessibility of the aneurysm, and variable risks of rupture and outcome. Results: A gain of at least one year of survival free of neurological sequelae is achieved by surgery compare d to natural history for patients whose life expectancy is 19.5 years, corresponding to age 63.5 years for males and 68 years for females. T he life expectancy at which a benefit accrues is longer (the patient i s younger) for larger, less accessible aneurysms, for lower rates of r upture, and for lesser risks of death or disability from rupture. Conc lusions: Elective surgery of unruptured asymptomatic aneurysms achieve s an increased survival over the natural history of at least one year free of neurological sequelae in patients whose life expectancy is 19. 5 years or more, using our baseline assumptions. Using equation [1], t he corresponding life expectancy producing this benefit can be calcula ted to account for the increased surgical risk of large, poorly access ible aneurysms and for factors affecting natural history.