1. Department of Neurology and Neurosurgery, South Central High Specialty Hospital, Pemex, Mexico
2. Neurosurgery and Neurology Department, Mexican Oil Company (Pemex) Villahemosa Regional Hospital, Instituto de Seguridad Social del Estado de Tabasco ‘Julian Manzur Ocaña Medical Center’, Tabasco, Mexico
3. Pathology Department, South Central High Specialty Hospital, Pemex, Mexico
4. South Central High Specialty Hospital, Pemex, Mexico
5. National Institute of Nutrition ‘Salvador Zubirán’, Mexico