[1] Univ Hosp Bonn, Dept Neurosurg, Venusberg Campus 1, D-53127 Bonn, Germany
[2] Goethe Univ Frankfurt, Dept Neurosurg, Schleusenweg 2-16, D-60529 Frankfurt, Germany
[3] Univ Hosp Bonn, Inst Med Biometry Informat & Epidemiol, Venusberg Campus 1, D-53127 Bonn, Germany
[4] Tech Univ Munich, Sch Med, Klinikum Rechts Isar, Dept Neurosurg, Ismaninger Str 22, D-81675 Munich, Germany
[5] Eberhard Karls Univ Tubingen, Dept Neurosurg, Hoppe Seyler Str 3, D-72076 Tubingen, Germany
[6] Univ Med Ctr Regensburg, Dept Neurosurg, Franz Josef Strauss Allee 11, D-93053 Regensburg, Germany
[7] Univ Hosp Essen, Dept Neurosurg & Spine Surg, Hufelandstr 55, D-45147 Essen, Germany
[8] Mainz Univ Hosp, Dept Neurosurg, Langenbeckstr 1, D-55131 Mainz, Germany
[9] Univ Ulm, BKH Gunzburg, Dept Neurosurg, Lindenallee 2, D-89312 Gunzburg, Germany
[10] Georg August Univ Gottingen, Dept Neurosurg, Robert Koch Str 40, D-37075 Gottingen, Germany
[11] Univ Hosp Bonn, Study Ctr Bonn SZB, Clin Study Core Unit, Venusberg Campus 1, D-53127 Bonn, Germany