SAN DIEGO—Unruptured aneurysms larger than 5 mm should be treated, according to analyses presented at the 2013 Annual Meeting of the American Society of Neuroradiology. The analyses examined a single-center cohort of nearly 3,400 patients with unruptured aneurysms who underwent either treatment or observation.
“Treatment has complications, and some patients deteriorate clinically,” said Yuichi Murayama, MD, Director of the Center of Endovascular Surgery at Jikei University in Tokyo. “However, we find that unruptured aneurysm treatment-related complications leave no effect on function, as measured by modified Rankin Scale scores. On the other hand, once an aneurysm ruptures, there is a high incidence of death and disability. Based on that [finding], we conclude [that] unruptured aneurysms larger than 5 mm should be treated.”
Annual Rupture Rate Was Less Than 1%
In the cohort of 3,395 patients with unruptured intracranial aneurysms (UIAs), 28% were treated. The remaining 72% were managed conservatively and underwent biannual 3D computed tomography angiography (CTA). Patients were referred to Jikei University between January 2003 and December 2012.
Most UIAs were measured using 3D CTA, which was considered more accurate and less invasive than magnetic resonance angiography (MRA). Patients were recommended for treatment with endovascular coiling or microsurgical clipping if the aneurysm was larger than 5 mm and could be treated safely, if multiple aneurysms were present and one had previously ruptured, or if the patient had a family history of subarachnoid hemorrhage. Endovascularly treated patients underwent MRA follow-up at three, six, and 12 months after treatment and subsequently underwent annual MRA and MRI studies. Surgically treated patients had angiography at 12 months after treatment and 3D CTA.
Almost 1,700 patients with UIAs who were not treated were followed during the 10-year period with CTA. Overall, 49 (2.9%) aneurysms ruptured, yielding an annual rupture rate of 0.8% per year. The average size of aneurysms in the treatment group was 7.8 mm, compared with 4.4 mm in the observation group. The frequency of treatment increased with aneurysm size. Approximately 10% of small aneurysms (4.9 mm in diameter or less), 50% of medium aneurysms (5.0 to 9.9 mm), and almost 100% of large (10.0 to 24.9 mm) and giant aneurysms (greater than 25 mm) were treated, said Dr. Murayama.
Annual rupture rates were 0.35% for small aneurysms, 2.2% for medium aneurysms, 10.75% for large aneurysms, and 50% for giant aneurysms. Although the risk of rupture of small aneurysms is low, 17 small aneurysms ruptured within the observation period. Furthermore, Dr. Murayama said that while most ruptures occurred within two years of discovery, even apparently stable aneurysms might rupture after two years. The most common sites for aneurysm rupture were the anterior cerebral, middle cerebral, vertebral, and posterior communicating arteries.
About 200 additional patients were followed with MRA rather than CTA, Dr. Murayama said. Ongoing analyses of the rupture rates in these patients may change the rupture rates for various aneurysm sizes.
A Previous Study Had Similar Findings
Dr. Murayama compared the results from his institution to the findings of another Japanese cohort in the UCAS study, which included 5,700 patients with almost 6,700 aneurysms enrolled from 283 medical centers. The annual risk of rupture for small aneurysms was 0.36%, which was similar to that found by the Jikei group (0.35%). The annual risk for 7- to 10-mm aneurysms was 1.7%, which was similar to that found by the Jikei group (1.5%).
The annual risk of rupture for aneurysms measuring 5 to 7 mm differed significantly between the two studies (0.5% in the UCAS cohort vs 2.3% in the Jikei cohort). “For [aneurysms of] this size, the decision to treat is difficult because the risk of rupture is relatively low, but treatment risk also exists. That is why, in our database, 50% of patients with 5- to 7-mm-sized aneurysms went to observation,” said Dr. Murayama.
Using 3D CTA, Dr. Murayama investigated whether UIAs grow. In the Jikei cohort, 10% of aneurysms grew in size (defined as a change of 1 mm or more between the baseline measurement and follow-up). “If you see a change in morphology, treat without delay,” he said.
—Amy Rothman Schonfeld
IMNG Medical News