Objective: Although the necessity of craniotomy for an unruptured cerebral aneurysm (UCA) is controversial, surgery is warranted if surgical risks are less than the risks of natural history. In this study, we investigated the need for craniotomy for UCAs on the basis of surgical risk.
Methods: History of cerebrovascular disorders, aneurysm site and size, surgical complications, and clinical outcome were investigated in 368 patients (134 men, 234 women; ages 31-79 yr) who underwent craniotomy for treatment of UCA at our institute between 1993 and 2000.
Results: We investigated 549 aneurysms. The mean size was 6.0 mm. Sites affected were the anterior cerebral artery (101 aneurysms), internal carotid artery (224 aneurysms), middle cerebral artery (201 aneurysms), and vertebrobasilar artery (23 aneurysms). The most common previous cerebrovascular disorders were subarachnoid hemorrhage (58 patients, 15.8%) and cerebral infarction (41 patients, 11.1%). Eight patients experienced permanent neurological deficits, for a total morbidity of 2.2%. One patient died, for a total mortality of 0.3%. For UCAs less than 10 mm in size, the morbidity was 0.6% and the mortality was 0%. For UCAs greater than 10 mm in size, the morbidity was 6.1% and the mortality was 1.2%. For UCAs in the anterior cerebral artery or middle cerebral artery, the morbidity was 0.3%. Temporary deficits were more frequently observed in patients older than 70 years of age than in patients 70 years of age or less.
Conclusion: Surgical treatment is a viable alternative for patients 70 years of age or less with UCAs less than 10 mm in size or UCAs located in the anterior cerebral artery or middle cerebral artery, because the surgical risk of treating such UCAs is sufficiently lower than the annual rupture rate of UCAs (2.3%) and the mental stress suffered by patients with untreated UCAs.