Brain tumours and surgery can cause extreme personality changes.
As a brain tumour grows, it puts pressure on surrounding tissue affecting the function, process or part of the body that is controlled by that area of the brain.
Personality changes are most common in people when the tumour is located in their frontal lobe, which controls personality, behaviour and emotions, problem solving and long-term memory.
Personality changes can also be caused by a tumour in the pituitary gland which controls hormone levels.
This can result from treatments including surgery, radiotherapy and chemotherapy.
Changes in personality and behaviour that have occurred as a direct or indirect result of these treatments usually pass gradually as people recover.
Large tumours can have a greater effect as they affect a greater area. However, even a small tumour in a key structure of the brain can have a significant impact.
Personality changes might also be experienced as a natural reaction to the diagnosis and treatment.
The emotional impact of the diagnosis, undergoing treatment, and the lifestyle changes that are often necessary for a person living with a brain tumour, can affect mood, general persona and can cause a person to become more irritable.