Defining the natural history of unruptured aneurysms.

Abstract

Despite advances in neurosurgical technique, neuroanesthesia, and neurocritical care and the evolution of endovascular therapy, aneurysmal subarachnoid hemorrhage (SAH) continues to be associated with poor outcome in a majority of patients. The 30-day mortality rate for SAH approaches 50%,1,2 and nearly one half of survivors suffer major neurologic morbidity. These dismal outcomes are especially significant since SAH affects a younger cohort than ischemic stroke, and the impact is magnified in terms of lost quality life-years. On the basis of an annual incidence of 10/100 000, it is estimated that nearly 30 000 Americans will have an aneurysmal SAH each year.3 Although prevention of SAH would seem to be the most effective strategy for reducing morbidity,4 the optimal management of patients with unruptured cerebral aneurysms remains controversial and requires a precise assessment of the risks for various treatment strategies and accurate knowledge of the natural history of the disease process. Unfortunately, the natural history of unruptured cerebral aneurysms is poorly understood. Until recently, few systematic studies have enrolled a sufficient number of patients for follow-up, and larger retrospective population analyses2,5 were done prior to the advent of current imaging modalities. Five years ago, the first phase of the International Study of Unruptured Intracranial Aneurysms (ISUIA) study provided a retrospective analysis of previously identified patients with unruptured aneurysms not receiving treatment, as well as a temporal snapshot of a cohort of patients followed prospectively over a 4-year period.6 The study reported what many considered to be remarkably low rates of aneurysm rupture (especially for aneurysms <10 mm in diameter) and a remarkably high rate of complications for surgical treatment, thus prompting a longer-term …