Brain aneurysms — even small ones — are more likely to rupture if they are growing, a new study has shown. The discovery counters current guidelines and emphasizes the need for regular monitoring and earlier treatment.
"Our results suggest that all aneurysms can grow, and all can rupture but they are more likely to rupture if they are growing. We conclude that all aneurysms of any size need to be followed. If they are growing then treatment should be considered. Following patients is not such a big deal. It only involves an annual outpatient CT scan. This should not be prohibitively expensive," lead investigator J. Pablo Villablanca, MD, University of California Los Angeles Medical Center, told Medscape Medical News.
The study was published online in Radiology on July 2.
Catastrophic Event
Dr. Villablanca explained that the rupturing of brain aneurysms has an extremely high mortality rate.
"In North America there are about 30,000 ruptures a year. Of these [patients] about 70% die, so it is a catastrophic event and it is crucial to try and understand which aneurysms are at risk of rupturing."
The most authoritative study so far — ISUIA, conducted in 2003 — showed that the largest aneurysms were the ones most likely to rupture, he noted.
"In their population of 1500 patients there were no ruptures of aneurysms of less than 7 mm. So because of this it is now recommended to follow more closely and consider treatment of aneurysms larger than 7 mm."
For the current study Dr. Villablanca and colleagues looked at a group of 165 patients who had a total of 258 cerebral aneurysms, which had been found incidentally upon scanning for something else. So these patients did not generally have symptoms. They were scanned once a year. Results showed that 46% of aneurysms were growing, a rate Dr. Villablanca said was higher than expected.
In the mean 2.2-year follow-up, 4 aneurysms ruptured, of which 3 were growing and saccular aneurysms. The 1 nongrowing aneurysm that ruptured was a fusiform type.
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Dr. J. Pablo Villablanca |
Twelve-Fold Increase in Rupture Risk
The rupture rate was 2.4% per patient per year if the aneurysm was growing vs 0.2% if not growing (P = .034).
"The 2.4% rupture rate is not that high but is 12-fold higher than if there was no growth," said Dr. Villablanca. Tobacco smoking and initial size were independent risk factors for aneurysm growth and predicted 78.4% of growing aneurysms.
Three of the four aneurysms that ruptured were under the 7 mm threshold that has until now been used as an indication for treatment.
"These patients would not have been picked up under current recommendations unless they had developed symptoms. But none of the patients in this study with rupture had symptoms before the rupture," Dr. Villablanca said.
Although growth was defined as 5% or more increase in volume, all 3 saccular aneurysms that ruptured showed at least a 30% increase in volume. Because of the small numbers of ruptured aneurysms in this study, it was not possible to determine statistically valid values for minimal growth, growth rate, or time to growth that increase risk for rupture, the researchers note.
The investigators are now extending follow-up and increasing sample size to see if they can determine these values.
Radiology. Published online July 2, 2013. Abstract