[1] UNIV GRAZ KLIN,DEPT NEUROSURG,GRAZ,AUSTRIA
[2] UNIV LUND HOSP,DEPT NEUROSURG,S-22185 LUND,SWEDEN
[3] UNIV BERN KLIN,DEPT NEUROSURG,BERN,SWITZERLAND
[4] UNIV FREIBURG KLIN,DEPT NEUROSURG,FREIBURG,FED REP GER
[5] FREE UNIV BERLIN,DEPT NEUROSURG,D-1000 BERLIN 33,FED REP GER
[6] ELISABETHEN KRANKENHAUS,DEPT NEUROSURG,RAVENSBURG,FED REP GER