1. Department of Surgery, Hanoi Medical University
2. Department of Neurosurgery I, Viet Duc University Hospital
3. Department of Neurosurgery and Spine Surgery, Hanoi Medical University Hospital, Hanoi
4. Department of Surgery, Can Tho Univeristy of Medicine and Pharmacy, Can Tho, Vietnam
5. Department of Neurosurgery, Tulane University, Louisiana, USA