1. Division of Neurosurgery, Department of Neurosciences, Philippine General Hospital, University of the Philippines Manila, Manila, Philippines;
2. Department of Anatomy, College of Medicine, University of the Philippines Manila, Manila, Philippines;
3. Neurosurgery Section, Department of Surgery, Bicol Regional Hospital and Medical Center, Legazpi City, Philippines;
4. Brain and Spine Institute, Cardinal Santos Medical Center, San Juan, Philippines;
5. Section of Neurosurgery, Department of Neurosciences, Makati Medical Center, Makati City, Philippines;
6. Department of Neurosurgery, Davao Doctors Hospital, Davao City, Philippines