Rationale for treating unruptured intracranial aneurysms: actuarial analysis of natural history risk versus treatment risk for coiling or clipping based on 14,050 patients in the Nationwide Inpatient Sample database.

Objective: The treatment of small unruptured intracranial aneurysms has been questioned based on the results of the International Study of Unruptured Intracranial Aneurysms. Our objective was to compare natural history rupture risk versus treatment risk for coiling and clipping small unruptured aneurysms using data in the Nationwide Inpatient Sample database.

Methods: Data for clipping and coiling of unruptured aneurysms was collected from the Nationwide Inpatient Sample from 2002-2008. Treatment risks were adjusted for age, gender, and medical comorbidities. Logistic regression models were used to create curves depicting the estimated probability of poor outcome as a function of patient age for clipping and coiling. These treatment risk curves were compared against natural history actuarial risk curves calculated from four prominent studies.

Results: There were 14,050 hospitalizations: 7439(53%) coiling; 6611(47%) clipping. For patients who underwent coiling or clipping, the mortality rate was 2.17% and 2.66%, and the morbidity rate was 2.16% and 4.75%, respectively. The adjusted risk of poor outcome from clipping and coiling, when modeled against most natural history studies, demonstrates a treatment benefit for clipping for patients <70 years and for coiling patients <81 years. Models using the International Study of Unruptured Intracranial Aneurysms data demonstrate a treatment benefit for clipping for patients <61 years and for coiling for patients <70 years.

Conclusions: Both clipping and coiling of unruptured intracranial aneurysms are safe. This analysis demonstrates rationale for clipping small unruptured aneurysms in patients <61-70 years and coiling small unruptured aneurysms in patients <70-80 years. Treatment beyond these age ranges is associated with increased risk of poor outcome.