Surgical Clipping of Very Small Unruptured Intracranial Aneurysms: A Multicenter International Study

BACKGROUND: Treatment of very small unruptured intracranial aneurysms (VSUIAs, defined as <= 3 mm) can be indicated in selected circumstances. The feasibility and outcomes of endovascular therapy for VSUIAs have been recently published; however, the efficacy and complication rate of surgical clipping has not been reported in any large series to date. OBJECTIVE: We conducted a multicenter study to examine surgical outcomes for VSUIAs. METHODS: All consecutive patients undergoing surgery for a VSUIA in 4 neurosurgical centers between October 2001 and December 2012 were retrospectively analyzed. RESULTS: In the study, 183 patients (128 women, mean age 51.3 years) were treated with 190 procedures for a total of 228 aneurysms. Most were anterior circulation aneurysms (n = 215). The majority were directly clipped (n = 222, 97.4%), with coagulation or wrapping in the remainder. After 1 reoperation for incomplete clipping, postoperative imaging of 225 aneurysms confirmed complete occlusion in 221 (98.2%), 1 neck remnant (0.44%), and 3 partial occlusions (1.3%). Mortality was 0%. Early postoperative neurological deficit developed in 12 patients (6.6%); posterior circulation location was a significant risk factor for early neurological deficit (P<.001). Middle cerebral artery aneurysms had the lowest rate of postoperative deficits at 1.5% (P =.023). After the initial 30-day perioperative period, all deficits related to treatment of posterior circulation aneurysms recovered; overall neurological morbidity decreased to 2.7% with no mortality. CONCLUSION: VSUIA clipping is highly effective and is associated with a low morbidity rate. For VSUIAs selected for treatment, our data support surgical clipping as the modality of choice.