Treatment outcomes of surgical clipping for unruptured anterior circulation aneurysm-single institute experiences in the era of neurophysiologic monitoring and endovascular treatment.

Recently, the treatment of intracranial aneurysms entered a new phase due to safe surgical tool such as neurophysiologic monitoring and challenged by endovascular treatment. To determine the safety of clipping surgery in the modern era, we reviewed our experiences of simple unruptured anterior circulation aneurysm surgery which is commonly performed in many places. We retrospectively reviewed 610 consecutive patients who were treated with surgical clipping under motor evoked potential (MEP) monitoring for a tiny to large anterior circulation aneurysm in a single institute between 2008 and 2012. MEP changes were identified in 40 cases (6.6 %). MEP deterioration was associated with remote site epidural hematoma (n = 1), anesthesia (n = 2), temporary clipping (n = 21), and permanent clipping (n = 16). Despite that no persistent MEP deterioration was noted after prompt corrective measures, 56 (9.2 %) patients showed symptomatic (n = 14) and asymptomatic (n = 42) radiologic abnormalities. Anterior cerebral artery (ACA) aneurysm was associated with a higher radiologic complication rate (Fisher's exact test, P < 0.05). Two (0.3 %) patients showed severe morbidity (mRS >2) at latest follow-up. MEP monitoring can be helpful in preventing postoperative motor deterioration but seems to have some limitations. Although the permanent morbidity rate was low, a significant clinical (2.3 %) or radiologic (9.2 %) abnormality rate was identified even in simple aneurysm clipping that should be taken into account when performing interdisciplinary treatment planning and patient counseling. Also, direct vascular monitoring or new neurophysiologic monitoring techniques are needed to reduce surgical complications, especially in ACA aneurysm surgery.