Treatments for unruptured intracranial aneurysms

Background: Unruptured intracranial aneurysms are relatively common lesions in the general population, with a prevalence of 3.2%, and are being diagnosed with greater frequency as non-invasive techniques for imaging of intracranial vessels have become increasingly available and used. If not treated, an intracranial aneurysm can be catastrophic. Morbidity and mortality in aneurysmal subarachnoid hemorrhage are substantial: in people with subarachnoid hemorrhage, 12% die immediately, more than 30% die within one month, 25% to 50% die within six months, and 30% of survivors remain dependent. However, most intracranial aneurysms do not bleed, and the best treatment approach is still a matter of debate.

Objectives: To assess the risks and benefits of interventions for people with unruptured intracranial aneurysms.

Search methods: We searched CENTRAL (Cochrane Library 2020, Issue 5), MEDLINE Ovid, Embase Ovid, and Latin American and Caribbean Health Science Information database (LILACS). We also searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform from inception to 25 May 2020. There were no language restrictions. We contacted experts in the field to identify further studies and unpublished trials.

Selection criteria: Unconfounded, truly randomized trials comparing conservative treatment versus interventional treatments (microsurgical clipping or endovascular coiling) and microsurgical clipping versus endovascular coiling for individuals with unruptured intracranial aneurysms.

Data collection and analysis: Two review authors independently selected trials for inclusion according to the above criteria, assessed trial quality and risk of bias, performed data extraction, and applied the GRADE approach to the evidence. We used an intention-to-treat analysis strategy.

Main results: We included two trials in the review: one prospective randomized trial involving 80 participants that compared conservative treatment to endovascular coiling, and one randomized controlled trial involving 136 participants that compared microsurgical clipping to endovascular coiling for unruptured intracranial aneurysms. There was no difference in outcome events between conservative treatment and endovascular coiling groups. New perioperative neurological deficits were more common in participants treated surgically (16/65, 24.6%; 15.8% to 36.3%) versus 7/69 (10.1%; 5.0% to 19.5%); odds ratio (OR) 2.87 (95% confidence interval (CI) 1.02 to 8.93; P = 0.038). Hospitalization for more than five days was more common in surgical participants (30/65, 46.2%; 34.6% to 58.1%) versus 6/69 (8.7%; 4.0% to 17.7%); OR 8.85 (95% CI 3.22 to 28.59; P < 0.001). Clinical follow-up to one year showed 1/48 clipped versus 1/58 coiled participants had died, and 1/48 clipped versus 1/58 coiled participants had become disabled (modified Rankin Scale > 2). All the evidence is of very low quality.

Authors' conclusions: There is currently insufficient good-quality evidence to support either conservative treatment or interventional treatments (microsurgical clipping or endovascular coiling) for individuals with unruptured intracranial aneurysms. Further randomized trials are required to establish if surgery is a better option than conservative management, and if so, which surgical approach is preferred for which patients. Future studies should include consideration of important characteristics such as participant age, gender, aneurysm size, aneurysm location (anterior circulation and posterior circulation), grade of ischemia (major stroke), and duration of hospitalizations.