The results suggest that follow-up screening intervals could be lengthened to 5-10 years.
De novo aneurysm formation occurs in only a small percentage of patients in the years after diagnosis of ruptured or unruptured aneurysm, according to the results of a meta-analysis published online July 6, 2018, in the Journal of Neurosurgery. Based on this infrequent occurrence, researchers say routine screening for new aneurysms can be scheduled at 5- to 10-year intervals.
“A vast majority of de novo aneurysms were found at more than 5 years after diagnosis of the index aneurysm and few ruptured,” write [LM1] Enrico Giordan, MD (Mayo Clinic, Rochester, MN), and colleagues. “Among those aneurysms that ruptured, the mean time to rupture was greater than 10 years.”
Giordan and colleagues conducted a systematic review and meta-analysis that included data on 14,968 patients with aneurysm from 35 studies drawn from multiple databases. All patients had received > 1 year of follow-up imaging.
Low Yield Likely With Routine Screening
During a mean follow-up of 8.3 years, the overall incidence of de novo aneurysms was 2%. This translated to an estimated incidence density of 0.3% per patient-year.
When the researchers compared patients with a history of ruptured aneurysm vs those with unruptured aneurysm, they found no difference in the rate of de novo aneurysm (3% at 8.5 years and 3% at 5.8 years, respectively).
Twenty-seven of the 35 studies contained information on timing of de novo aneurysm. In these studies, the mean time to identification was 8.3 years, with 88.8% of de novo aneurysms being found at 5 years or later.
Twenty-six studies contained information on timing of aneurysm rupture. Fifty-five patients had de novo aneurysm rupture over a mean follow-up of more than 10 years. Of these patients, 58% had the rupture occur after more than 10 years.
“The findings from the current analysis should be taken in the context of the goal of screening brain aneurysm patients—preventing aneurysmal subarachnoid hemorrhage,” Giordan and colleagues write. They add that the results “are important as they suggest that routine screening for de novo aneurysms is likely of low yield and could be performed at time intervals of at least 5 to 10 years, with more frequent screening possibly indicated for patients with certain risk factors.” The latter group would include active smokers, those with a family history of intracranial aneurysms, and patients diagnosed with multiple aneurysms.
The researchers also acknowledged that one limitation of the analysis is the wide variety of screening modalities used in the included studies, which could “introduce some error or bias, along with the possibility of inter- and intraobserver variability in assessing true de novo aneurysms.”
In addition, few of the studies had mean follow-up times of longer than 10 years. “Thus, we could be underestimating the rate of de novo aneurysm formation,” Giordan et al write. “There are no reliable methods to ascertain that presence of publication bias in noncomparative series; however, publication bias remains possible.”
The current findings corroborate those of previously published cost-effectiveness and decision-tree analyses suggesting that de novo aneurysm formation and rupture are relatively rare, they conclude.
Giordan E, Lanzino G, Rangel-Castilla L, et al. Risk of de novo aneurysm formation in patients with a prior diagnosis of ruptured or unruptured aneurysm: systematic review and meta-analysis. J Neurosurg. 2018;Epub ahead of print.
Giordan reports no relevant conflicts of interest.