Response to Letter to the Editor “Preoperative Digital Subtraction Angiography in Incidental Unruptured Intracranial Aneurysms”

Abstract

Dear Editor, we read Mr. Malhotra's valuable comments and questions [1] with great interest and would like to thank him for his interest in our study [2]. The primary intention of this prospective study was to scrutinize the "good clinical practice" of performing a four-vessel angiography in all patients with the incidental finding of an unruptured intracranial aneurysm in magnetic resonance imaging (MRI).For us, the most interesting piece of information we learned from our study was the very low percentage of aneurysms actually being missed by routine MRI when read by an experienced neuroradiologist. Furthermore, we learned that the vast majority of aneurysms that remained undetected occurred in the patient cohort bearing more than one aneurysm on the initial MRI scan. Therefore, we conclude that a four-vessel angiogram actually does add more information in this group of patients. Moreover, all aneurysms missed on MRI were relatively small in size. As summarized recently, the natural history of small and very small aneurysms is not well understood [3] and there is no general recommendation for treatment or for follow-up [4]. It is also a well-known fact that the annual risk of hemorrhage is lower for small aneurysms when compared to large aneurysms, as again proven by the study of Malhotra et al. [3]; however, although size is one of the strongest predictors, even small aneurysms do rupture [5]. Growth and risk of hemorrhage does not only depend on the mere diameter but also on factors concerning the configuration and localization of the aneurysm as well as patient characteris-M. Herzberg