Brain disorder is a generic term for any and all of the numerous disorders associated with the human brain, including infections, stroke, seizures, trauma, cancer and other life-threatening diseases, autoimmune diseases, inherited disorders, neurodegenerative conditions, and growths such as tumors.
Most forms of mental illness, particularly those that are chronic, severe, or progressively debilitating (such as untreated schizophrenia) are also categorized as brain disorders. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) is the most commonly used diagnostic reference tool in the United States for psychiatric illness; the International Classification of Diseases, Part 10 (ICD-10), which is used for both physical and mental illness, is used worldwide.
There are several types of infectious process that may directly affect brain function or cause brain diseases, the most common of which are: brain abscesses or infections within the structures of the brain; encephalitis, in which the brain tissue becomes inflamed as the result of a viral syndrome; and meningitis, which may be caused either by bacterial infection or a viral syndrome and results in inflammation of the lining of the spinal cord or brain tissue.
When an area of the brain experiences an abrupt interruption or cessation of blood flow during a stroke, the affected tissue often dies or is irreparably damaged, affecting the part(s) of the body controlled by that brain region. Bleeding in the brain, which may cause stroke or brain damage, can be caused by a ruptured aneurysm (extremely swollen blood vessel), subdural hematoma (usually trauma-related bleeding on the surface of the brain causing increased intracranial pressure), epidural hematoma (bleeding between the skull and the dura matter covering the brain), or any other type of bleeding inside the brain (intracerebral hemorrhage). Swelling in the brain caused by any means causes increased pressure and may result in stroke as well.
Seizures, whether caused by a seizure disorder such as epilepsy or occurring in isolated form such as febrile seizures (seizures caused by a very high fever during an illness), are considered brain disorders. When not well controlled or when lasting for more than just a couple of minutes, seizures can cause lasting damage to the brain. Seizures may be caused by infection, tumors, increased intracranial pressure, infections of the brain, stroke, or head trauma as well.
A significant head injury may result in increased pressure or bleeding within the brain. Traumatic brain injury, when moderate or severe, often results in lasting damage to the brain with resultant loss of cognitive or other (motor, visual, etc.) function, possible seizure disorder, mood and personality changes, and loss of function in the body regions associated with the damaged brain area. A concussion, depending upon severity, typically results in severe headaches and/or vision and memory problems and causes temporary changes in brain function; it may be associated with temporary loss of consciousness and changes in mental status.
Any abnormal growth within the brain or skull is called a tumor, but not all brain tumors are caused by cancer. Any unusual growth or excess fluid within the brain causes increased intracranial pressure. There are many types of cancer that either originate within the brain or metastasize from elsewhere (produce secondary tumors) and create cancerous lesions in the brain. Hydrocephalus is an increased amount of cerebrospinal fluid remaining inside the skull rather than circulating. It causes increased pressure and may result in permanent damage unless removed. Quite often in cases of hydrocephalus, a surgical procedure is performed in which a tube called a shunt is placed inside the skull to drain excess fluid from the brain into the abdominal cavity, where it can be harmlessly reabsorbed. A shunt may be permanent or a temporary drain may be used, depending on the cause of the hydrocephalus.
See also Alzheimer's disease ; Brain injuries ; Dementia ; Minimal brain dysfunction .
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