Non traumatic brain injury
An internal event caused the injury.
An aneurysm is weak bulging spot in the wall of an artery. It happens when the pressure of blood passing through has forced a weakened part of the artery to balloon outward. An aneurysm can cause brain injury because the blood flow through the artery can thin and stretch the bulging part of the artery wall, eventually causing it to rupture. This may lead to either stroke or bleeding in the brain.
Our brain needs oxygen to function, and because it is unable to store oxygen, when we find ourselves in situations where the brain isn't getting it - we are likely looking at brain damage after a couple minutes of oxygen deprivation. (Unless you are a free diver). When would we experience anoxia, or oxygen deprivation? Near drowning, severe asthma attack, smoke inhalation, obstructed airway/choking, and poisoning, to name a few.
A stroke happens when the blood supply to the brain is cut off or interrupted. Without blood (and the oxygen the blood brings), the cells in the brain start to die and the functions dependent on that area of the brain can be lost. Injury is dependent on where the stroke occured and how much damage was sustained. Strokes are also known as cerebrovascular accidents (CVAs) or as a brain attack, and are divided into hemorrhagic, ischemic and transient ischemic attacks (TIAs or mini-strokes). See here for more information on stroke.
A brain tumour is a mass of abnormal cells in or around the structure of the brain. Brain tumours can be either benign or malignant. The Brain Tumour Foundation of Canada states there is over 120 types of brain tumours, and has a concise Brain Tumour 101 resource. HealthLink BC states that when "a tumor grows into or presses on an area of the brain, it may stop that part of the brain from working the way it should. Both benign and malignant brain tumors cause signs and symptoms and need treatment." Read more here.