What causes brain tumors?
For most patients the cause is unknown.
The only definitive environmental risk factor for brain tumors is ionizing radiation.
An elevated risk of several brain tumors such as meningiomas, gliomas, and nerve sheath tumors has been seen in cohort studies of atomic bomb survivors and childhood cancer survivors who received cranial radiation.
Additionally, a small percentage of brain tumors are related to specific genetic syndromes such as neurofibromatosis type 1, neurofibromatosis type 2, Turcot syndrome, Gorlin syndrome, von Hippel–Lindau syndrome, and Li–Fraumeni syndrome.