Cerebral Aneurysms: To Screen or Not to Screen?
Abstract & Commentary
By Dana Leifer, MD, Associate Professor, Neurology, Weill Medical College of Cornell University. Dr. Leifer reports no consultant, stockholder, speaker's bureau, research, or other financial relationship related to this field of study.
Synopsis: Screening patients with a history of cerebral aneurysm and screening relatives of patients with familial aneurysms can detect new or recurrent aneurysms that may benefit from treatment.
Source: Wermer MJ, et al. Follow-Up Screening After Subarachnoid Hemorrhage: Frequency and Determinants of New Aneurysms and Enlargements of Existing Aneurysms. Brain. 2005;128:2421-2429.
Subarachnoid Hemorrhage (SAH) is one of the most feared neurologic problems because of its sudden onset, its often catastrophic effects, and its propensity to strike adults in the prime of life. Usually it strikes without warning, but patients who have had one aneurysmal SAH are at increased risk for another hemorrhage, even if the aneurysm that ruptured has been clipped or obliterated by endovascular coiling. In addition, cerebral aneurysms may be familial. When 2 first-degree relatives have cerebral aneurysms, other family members are at increased risk. The ability of CT angiography (CTA) and MR angiography (MRA) to detect aneurysms non-invasively makes it more feasible to screen people at risk for SAH hemorrhage than in the past when catheter angiography was the only way to diagnose aneurysms reliably. In this background, Wermer and colleagues have published important work on the detection of aneurysms in patients with a personal or family history of aneurysm.
They performed follow-up CTA on 610 patients with ruptured aneurysms that were surgically clipped (Brain. 2005:128:2412-2429). The mean interval between SAH and the follow-up CTA was 8.9 years, with a range from 2.3 to 18.8 years. They detected 129 aneurysms that were not previously identified in 96 patients, for an overall incidence of 16%; 24 of the aneurysms were at the clip site and 105 were remote from the clip site. Imaging studies from the time of SAH were available for review for 59 of the 105 remote aneurysms.
Nineteen of these newly detected remote aneurysms were truly new, and 40 were retrospectively found on the studies done at the time of the SAH. The incidence of new aneurysms increased over time. A new aneurysm was found in only 1 of 120 patients (0.8%) whose follow-up study was within 5 years of the SAH, in 8 of 365 (2.2%) with a follow-up study within 10 years of the SAH, and in 14 of 610 (2.3%) overall. The mean interval between SAH and detection of a new aneurysm remote from the original clip site was 9.9 years.
The incidence of recurrent aneurysms at the clip site also increased over time, with new aneurysms in only 2 of 120 patients (1.7%) after 5 years, 10 of 365 (2.7%) after 10 years, and 24 of 610 (3.9%) overall. The mean interval between SAH and detection of a recurrent aneurysm at the clip site was 10.6 years.
These results suggest that aneurysm formation continues over many years, both at the site of the original clipping and at remote sites. The results indicate that screening of patients with a history of ruptured aneurysms will identify new aneurysms, but the study does not provide clear data about whether these aneurysms need to be treated. In this regard, only 13 of the 105 newly identified aneurysms remote from the clip site were more than 5 mm in size, and only 1 of these was more than 10 mm. Of the 24 aneurysms at the clip site, 4 were more than 5 mm and only 1 was more than 10 mm.
Wermer et al also performed a multivariate analysis to look for risk factors that increase the chance of new or recurrent aneurysm growth. Smoking, the presence of multiple aneurysms at the time of SAH, and family history of intracranial aneurysms were all significantly associated with new or recurrent aneurysm formation, so patients with these characteristics may be the ones most likely to benefit from follow-up screening.
The identification of family history as a risk factor for recurrent aneurysm raises the issue of screening asymptomatic patients with a family history of aneurysms. In a related paper, the same group addressed this question (Stroke. 2003:34:2788-2791). Patients with 2 or more first-degree relatives with aneurysms were advised to have repeated screening by MRA or CTA at intervals of 5 years. Ten new aneurysms were detected in 9 of 102 patients. Six of the aneurysms were found in 83 patients with no prior history of aneurysm and with an initial negative screening MRA. Three of these 6 aneurysms were found on the first follow-up MRA and the other 3 on a second follow-up MRA. The remaining 4 aneurysms were found in 3 of the 19 patients with a prior history of aneurysm. Six of the 10 aneurysms that were identified were treated; 3 by coiling and 3 by clipping. The other 4 aneurysms were less than 4 mm in size, and are being followed with repeated imaging.
The finding that 3 of the 10 aneurysms that were found did not appear until the third screening MRA suggests that a strategy of repeated screening is a reasonable one to consider in patients with a family history of aneurysm. The data in this study also suggest that screening may be particularly important in middle-aged adults, as all of the aneurysms that were treated were found when patients were 45 years of age or older.
Taken together, these studies suggest that given the potentially devastating effects of SAH, repeated non-invasive screening deserves consideration both for patients with a history of prior aneurysm and for those with 2 or more first-degree relatives with aneurysms. The benefits of detecting and treating aneurysms need to be weighed on an individual basis against the costs of screening, the anxiety that may be caused by finding small aneurysms that do not need treatment, and the risks of treatment. Additional prospective studies may help to clarify the best approach for non-invasive screening for cerebral aneurysms.