Severe trauma is the most likely to be immediately fatal. However, any condition that affects the brain can cause death.
Glioblastoma multiforme (GBM) tumors are the most malignant of all brain tumors
Gliobastoma Multiforme
heart disease
dysentery
Damage to the cerebral cortex is least likely to be fatal; damage to the medulla is most likely to be fatal.
A rare, often fatal disease of the brain, characterized by gradual dementia and loss of muscle control that occurs most often in middle age and is caused by a slow virus
The common housefly
Schilder's disease is uniformly fatal.
cystic fibrosis
Eastern European Jews
Yes, it can be fatal.
In the United States, about 1 in every 30,000 people has Huntington's Disease.
Cardiovascular disease (and 2nd is cancers, with 3rd being strokes).
Meningitis means inflammation of the coverings of the brain. It can be caused by bacteria or viruses. It is a serious and potentially fatal disease if not promptly treated.