[1] Univ Helsinki, Cent Hosp, Dept Neurosurg, SF-00260 Helsinki, Finland
[2] Suleyman Demirel Univ Hosp, Dept Neurosurg, TR-32260 Isparta, Turkey
[3] Istanbul Univ, Dept Neurosurg, Cerrahpasa Med Fac Hosp, TR-34098 Istanbul, Turkey
[4] Univ Kentucky, Dept Neurosurg, Lexington, KY 40506 USA
[5] Duzce Med Fac Hosp, Dept Neurosurg, TR-81620 Duzce, Turkey
[6] Galeazzi Hosp, Dept Neurosurg, I-20161 Milan, Italy
[7] Le Scotte Hosp, Dept Neurosurg, I-53100 Siena, Italy