More patients undergoing brain–imaging scans are being diagnosed with small aneurysms, or enlargements of an artery, when tested for symptoms like severe headaches. These aneurysms can grow and rupture, causing significant disability and death. These aneurysms are often treated as soon as they are discovered to prevent these bad outcomes. However, a Yale researcher has found that the risk of small aneurysm rupturing may actually be quite low.

In the study, published in the journal Annals of Internal Medicine, Dr. Ajay Malhotra, associate professor of radiology and biomedical imaging, and the research team analyzed data from 26 published studies on the topic. They found, first, that the risk of small aneurysm growth and rupture was quite low: The growth rate for small and very small aneurysms was less than 3%, and the rupture rates were even lower — less than 1%. The growth rate and risk of rupture in aneurysms that are less than 7mm may vary, and very small aneurysms (<3 and <5mm) may have even smaller growth and rupture rates. The quality of the existing evidence however is limited and varied, note the researchers.

The study findings point to the need for better quality research, as well as a standard definition and measurement for aneurysm growth, said the researchers. Given the increasing use of brain imaging technologies and incidental findings of small intracranial aneurysms, doctors may need to consider these low rates of growth and rupture before recommending routine treatment or frequent imaging follow–up, said Malhotra.