The medical records of 312 patients who underwent surgical intervention for unruptured intracranial aneurysm by the same neurosurgeon between April 1979 and December 2000 were analyzed retrospectively to clarify the complexities of this treatment. Patients were divided into Groups I (earlier) to IV (later) according to the date of surgery. Outcome was evaluated as no change after surgery, transient postoperative deterioration (TD), or permanent deterioration (PD). Operative period, background disease, age, aneurysm location and size, postoperative results, and affecting factors were investigated. The overall rate of PD was 5%, including one death (0.3%), and the overall rate of TD was 11%. Cases of middle cerebral artery aneurysm and small aneurysm with diameters less than 10 mm in all locations showed favorable outcomes. There were no significant differences in operative results and period except the lower incidence of TD in Group IV. Surgical outcome was significantly correlated with aneurysm size. Vertebrobasilar artery aneurysm was associated with worse operative results. Most of the causes of PD were related to operative procedures, mainly perforator injury and general complications. Unruptured aneurysm can be treated safely, especially in cases of middle cerebral artery aneurysm and small aneurysm of less than 10 mm diameter in all locations. Larger aneurysms and vertebrobasilar artery aneurysm should be treated by experienced neurosurgeons.
2004 by The Japan Neurosurgical Society