[Very small intracranial aneurysms: Clip or coil]

Introduction: It is not unusual for very small aneurysms (≤3mm) to be responsible for subarachnoid haemorrhage. In addition, modern imaging has increased diagnosis of those that are asymptomatic. Because of their spatial configuration and thin and fragile walls, very small aneurysms can be a sizeable challenge for both open surgical and endovascular treatment. Based on recent literature data, the present manuscript reviews treatment indications and the choice of treatment strategy to occlude these particular aneurysms.

Methods: Literature review concerning surgical and endovascular treatment of very small aneurysms (≤3mm). Arterial dissections and blister aneurysms were excluded.

Results: We found no study that systematically and specifically assessed surgical treatment of very small aneurysms. Investigations of endovascular treatment are almost exclusively retrospective, usually evaluating a small number of patients, and are limited by selection bias. Despite often contradictory results, it appears that very small aneurysms carry a higher risk of rupture during endovascular procedures and higher ensuing mortality, as compared to larger aneurysms. The use of more flexible coils and additional endovascular tools appears to reduce this risk. There is no study comparing surgical to endovascular treatment.

Conclusion: Very small aneurysms carry higher treatment risks than larger aneurysms. A prospective randomised trial is justified for those very small aneurysms for which treatment is indicated.