Microsurgical clip ligation in the treatment of intracranial aneurysm shows long-term durability, with a small risk for recurrence when residual aneurysms are present after treatment, according to a new study.

“This is the largest study to date with the longest follow-up data that confirms the long-term efficacy of aneurysm clip ligation,” said first author Mason Brown, a medical student with the Indiana University School of Medicine, Indianapolis, in presenting the findings at the American Association of Neurological Surgeons (AANS) 83rd Annual Meeting.

Previous studies have estimated the recurrence risk with aneurysm clip ligation to be approximately 0.26% to 0.053% annually, and the risk for de novo aneurysm at 0.84% to 1.8% per year; however there is currently no standard protocol for the timing or length of follow-up after surgery, Brown said.

For the study, the researchers retrospectively reviewed records on 616 patients (mean age, 48 years) who underwent microsurgical clip ligation and follow-up imaging for more than 1 year following discharge from the university’s medical center.

Among the patients, 919 aneurysms were treated, including 753 that underwent surgical clip ligation for ruptured and unruptured aneurysms.

With angiographic imaging available on the aneurysms at a mean of 7.2 years after discharge, the authors found only one recurrent aneurysm (0.14%) of the 699 (92.2%) clipped aneurysms that showed no residua following the initial operation.

The recurrence rate was higher among the 59 (7.8%) known residual aneurysms following clip ligation, with 8 (13.6%) of the aneurysms regrowing and 4 requiring treatment.

Of 111 patients presenting with multiple aneurysms on admission, 8 (7.2%) had a de novo aneurysm formation on follow-up. Meanwhile, there were no de novo aneurysms among patients presenting with a single aneurysm on admission.

“Our results demonstrate a low recurrence of 0.14% to 13.6% after clip ligation, while recurrence rates after coil embolization can be as high as 30% to 40%,” Brown said.

Nevertheless, he underscored that the findings indicate that anything less that completely clipped aneurysms should have careful follow-up.

“There is a significant growth risk for residual aneurysms after incomplete clip ligation, and the findings necessitate continued follow-up, late angiographic imaging and further intervention.”

Adam S. Arthur, MD, MPH, from the Semmes-Murphey Clinic in Memphis, Tennessee, who co-moderated the session, agreed that the findings provide important insights on potential areas of risk after clip ligation.

“These findings document the low risk of aneurysm recurrence after clip ligation,” he told Medscape Medical News.

“Importantly, however, this recurrence risk is not zero. As we have developed new ways to treat aneurysms we have struggled to evaluate the long-term durability of these treatments.”

“It has become clear that we should also research the durability of the gold standard historical treatment for aneurysms, surgical clipping.”