Ignatius Ngene Esene1, Ali Kotb2, Hossam ElHusseiny2. 1. Department of Neurosurgery, Ain Shams University, Cairo, Egypt; Research Associate, Gamma Knife Center, Nasser Institute, Cairo, Egypt; Encyclopaedia Neurochirurgica, Paris, France. Electronic address: ignatiusesene@yahoo.co.uk. 2. Department of Neurosurgery, Ain Shams University, Cairo, Egypt.