Characteristics of the included early patient collective (1997 to 2003).

ACA: Anterior communicating artery, Anterior cerebral artery; ICA: Internal carotid artery; MCA: Middle cerebral artery; VA: Vertebral artery; BA: Basilar artery. Fisher-exact tests and Chi-Square tests examine the 0-Hypothesis H0 that there is no difference between the intervention modalities (endovascular group versus microsurgical group) regarding the ratios of the specific patient characteristics (e. g. ratio “WFNS°I-II” to “not WFNS°I-II” in the endovascular group versus ratio “WFNS°I-II” to “not WFNS°I-II” in the microsurgical group).