[1] Erasmus MC, Dept Neurosurg, Doctor Molewaterpl 40, NL-3015 GD Rotterdam, Netherlands
[2] Haaglanden Med Ctr, Dept Neurosurg, The Hague, Netherlands
[3] Univ Hosp Leuven, Dept Neurosurg, Leuven, Belgium
[4] Univ Hosp Bern, Dept Neurosurg, Bern, Switzerland
[5] Harvard Med Sch, Massachusetts Gen Hosp, Dept Neurosurg, Boston, MA 02115 USA
[6] Univ Calif San Francisco, Dept Neurosurg, San Francisco, CA USA