[1] Univ Helsinki, Helsinki Univ Hosp, Dept Neurosurg, Helsinki, Finland
[2] Univ Politecn Marche, Umberto Gen Hosp 1, Dept Neurosurg, Ancona, Italy
[3] Osped Riuniti Marche Nord, Dept Neurosurg, Pesaro, Italy
[4] Univ Andina Cusco, Ctr Invest Anat & Fisiol Alto Andina, Cuzco, Peru
[5] Univ Helsinki, Cent Hosp, Ctr Canc, Dept Radiat Oncol, Helsinki, Finland