Anoxic brain injuries are caused by a complete lack of oxygen being provided to the brain, which results in the death of brain cells after approximately four minutes of oxygen deprivation.
Anoxic brain injuries often cause an initial loss of consciousness, which can be short-term or long-term depending on severity and length of oxygen deprivation. Initial loss of consciousness may result in a comatose state. Other symptoms of an occurring anoxic brain injury may include slurring and difficulties with speech, confusion and disorientation or facial drooping.
Upon regaining consciousness, the effects and symptoms are often similar to that of a traumatic brain injury, depending on severity of the injury. More severe anoxic brain injuries may leave the patient in a vegetative state.
Anoxic and Hypoxic Brain Injury, Shepherd Center, https://www.shepherd.org/patient-programs/brain-injury/about/types-of-brain-injury/anoxic-hypoxic-brain-injury