[1] Univ Hosp Schleswig Holstein, Dept Neurol, D-24105 Kiel, Germany
[2] Univ Hosp Schleswig Holstein, Dept Neurosurg, D-24105 Kiel, Germany
[3] Univ Hosp Schleswig Holstein, Dept Neurosurg, Lubeck, Germany
[4] SHG Klin, Dept Neurosurg, Idar Oberstein, Germany
[5] Univ Essen Gesamthsch, Dept Neurol, D-4300 Essen, Germany
[6] Hannover Med Sch, Dept Neurosurg, D-3000 Hannover, Germany