Brain damage may occur due to a wide range of conditions, illnesses, or injuries. Possible causes of widespread (diffuse) brain damage include prolonged hypoxia (shortage of oxygen), poisoning, infection, and neurological illness. Common causes of focal or localized brain damage are physical trauma (traumatic brain injury), stroke, aneurysm, or neurological illness.

The extent and effect of brain injury is often assessed by the use of neurological examination, neuroimaging, and neuropsychological assessment.

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