Hakan Ak1, Tugay Atalay2, Ismail Gülşen3. 1. Department of Neurosurgery, Bozok University, School of Medicine, Yozgat, Turkey. Electronic address: nrsdrhakanak@yahoo.com. 2. Department of Neurosurgery, Bozok University, School of Medicine, Yozgat, Turkey. 3. Department of Neurosurgery, Yüzüncü Yıl University, School of Medicine, Van, Turkey.