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Our Stories

New findings challenge old notions of cerebral aneurysm development

Toronto, May 2, 2014

Dr. Loch Macdonald
Dr. Loch Macdonald

Cerebral aneurysms – bulges formed where the brain’s major blood vessels branch – can remain unruptured for years but may also cause life-threatening brain bleeds. Aneurysms are commonly believed to exist for decades and undergo only sporadic changes but new research suggests that cerebral aneurysms seem to change more rapidly than previously assumed and develop rather recently in a patient’s life.

The research, which was published in the journal Stroke, was conducted by an international research group led by neurosurgeons from Toronto’s St. Michael’s Hospital and Germany’s Heinrich-Heine University in Düsseldorf.

The researchers confirmed that brain arteries and aneurysms consist of very different proteins. Blood vessels in the brain are made up of a complex network of tissue layers and cells, which help to preserve the vessel wall’s integrity. But unlike the blood vessels they arise from, cerebral aneurysms are made up almost entirely of collagen type I.

Based on the knowledge that cerebral aneurysms had such different composition, the researchers used radiocarbon dating to determine the age of the collagen type I that they’d extracted from ruptured and unruptured cerebral aneurysms.

“In nearly all of the aneurysms, the collagen type I was quite young – less than five years old,” explained Dr. Nima Etminan, primary investigator and former cerebrovascular fellow at St. Michael’s Hospital. “This does not necessarily imply that all cerebral aneurysms are less than five years old, but it does indicates that cerebral aneurysms are dynamic structures and undergo continuous structural change.”

The collagen type I in the cerebral aneurysms was young regardless of the patient’s age or the specific traits of the aneurysms – such as shape, size and whether or not it had ruptured.

But there was one difference.

“The aneurysms in patients who had a history of risk factors had significantly younger collagen than those of patients with no increased risk factors,” said Dr. Loch Macdonald, senior author and neurosurgeon who also holds the Keenan Chair in Surgery at St. Michael’s Hospital. “This suggests that patients with unruptured cerebral aneurysms may benefit from regulating high blood pressure and quitting smoking.”

Radiocarbon dating can be used to determine when collagen in an aneurysm was last formed, but further research is needed before researchers might be able to determine exactly when aneurysm formation begins.

This research was funded by the Physicians Services Incorporated Foundation, National Institute of General Medical Sciences, the Brain Aneurysm Foundation, Canadian Institutes of Health Research, and the Heart and Stroke Foundation of Ontario.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

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