1. Departments of Neurosurgery, Faculty of Medicine, University of Cartagena, Cartagena de Indias, Colombia
2. Departments of Neurosurgery, National Center for Neurological Sciences, Shaab Hospital, Khartoum, Sudan
3. Departments of Neurosurgery, Instituto Nacional de Neurologia y Neurocirugia, Hospital Angeles de Pedregal, Mexico City, Mexico