Growth, not just size, boosts brain aneurysms' risk of bursting

Brain aneurysms of all sizes - even small ones the size of a pea - are up to 12 times more likely to rupture if they are growing, according to a new study from University of California, Los Angeles.
 
Published 2 July in the online edition of the journal Radiology, the discovery counters current guidelines suggesting that small aneurysms pose a low risk for rupture, and it emphasizes the need for regular monitoring and earlier treatment.
 
"Until now, we believed that large aneurysms presented the highest risk for rupture and that smaller aneurysms may not require monitoring," said lead author Dr. J. Pablo Villablanca, chief of diagnostic neuroradiology at the David Geffen School of Medicine at UCLA. "Our findings show this is not the case and shed light on additional risk factors for rupture in aneurysms of all sizes."
 
An aneurysm occurs at a weak spot in an artery that supplies blood to the brain. The artery wall bulges outward, creating a balloon filled with blood. If an aneurysm ruptures, blood leaks into or around the brain, which can cause stroke, paralysis, brain damage or death.
 
An estimated 6 million people in the US, one in 50, live with a brain aneurysm, most with no symptoms. But brain aneurysms rupture in some 30,000 Americans each year. The prognosis is grim: About 40 per cent die before reaching the hospital, and another third die within the first 30 days post-rupture. The majority of those who survive are left with permanent brain damage and physical disability.
 
Villablanca and his colleagues imaged the brain blood vessels of 165 patients with 258 asymptomatic aneurysms using a noninvasive method called computed tomography angiography, or CTA. Patients underwent CTA scans every six or 12 months.
 
In 38 of the patients, the researchers saw growth in 46 aneurysms - nearly 18 percent of all the aneurysms. Three of the growing aneurysms ruptured; all were smaller than 7 millimeters when the patient enrolled in the study.
 
"Our study shows that the size of the aneurysm is not as important as we once thought," Dr. Villablanca said. "Any aneurysm is capable of growth and requires follow-up imaging."
 
Compared with the aneurysms that did not increase in size, growing aneurysms were associated with a 12-fold higher risk of rupture. The researchers calculated the risk of rupture for growing aneurysms at 2.4 percent per patient-year, versus 0.2 percent for aneurysms without growth.
 
"Our data emphasize the importance of long-term follow-up imaging to watch for possible growth in all unruptured aneurysms, including small lesions," Villablanca said.
 
In a secondary finding, the researchers reported that tobacco smoking and an aneurysm's initial larger size were independent factors predicting aneurysm growth. These combined risk factors were linked to nearly 80 percent of all aneurysm growth in the study.
 
"Our findings correlated a higher risk of rupture to the combined factors of smoking, aneurysm growth and larger aneurysm size," Villablanca said. "Patients who smoke and have growing aneurysms may require earlier treatment, such as brain surgery or endovascular coiling."
 
The research was supported by a grant from the National Institute of Biomedical Imaging and Bioengineering.
 
Villablanca's co-authors included Dr. Gary Duckwiler, Dr. Reza Jahan, Dr. Satoshi Tateshima, Dr. Neil Martin, Dr. John Frazee, Dr. Nestor Gonzalez, James Sayre and Dr. Fernando Vinuela, all from UCLA.