Brain Tumor - Causes The exact cause of most brain tumors is unknown. A small number of brain tumors occur in people who have known genetic conditions, such as neurofibromatosis, tuberous sclerosis, Li Fraumeni syndrome or von Hippel Lindau syndrome. Other factors that have been suggested as possible causes of brain tumors include certain types of virus like HIV. Brain Tumor - References Published on Mar 02, 2016Last Updated on Apr 25, 2018