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Brain Disease and Injury

Reviewed by Psychology Today Staff

The depth of the brain’s unconscious, taken-for-granted functions and complex conscious abilities comes into sharp relief when they are disrupted in cases of brain disease and injury. Whether the damage unfolds in slow motion over the course of decades or begins to alter the brain in an instant, the loss or distortion of mental function that neurological conditions can wreak can be life-changing.

That’s why efforts toward prevention, diagnosis, and treatment are so crucial. Many brain diseases cannot be cured, and sudden brain injuries can have lasting effects. But for many conditions, from dementia-causing diseases such as Alzheimer’s disease to traumatic brain injury, scientists and health experts point to ways to promote brain health and reduce risk. And for many conditions, timely diagnosis and intervention may influence the course of the illness and the extent of the long-term harm done.

Neurological Diseases

There are hundreds of different diseases that can affect the function of the brain and nervous system, leading to many possible physical, cognitive, and emotional difficulties—from impaired movement or speech to deficits in reasoning, memory, and mood. Some neurologic diseases are present at birth, while many do not manifest until later in life.

Major categories of neurological diseases include:

  • Neurodegenerative diseases, which involve the breakdown and death of nerve cells over time. The most common of these are Alzheimer’s disease, marked by a decline in memory and other cognitive functions, and Parkinson’s disease, a movement disorder. The risk of symptoms increases with age, though some conditions that involve nerve cell degeneration, such as Huntington’s disease, are due to a genetic defect. Other degenerative diseases include amyotrophic lateral sclerosis (ALS), multiple sclerosis, and Lewy body disease.
  • Stroke, which affects blood vessels that provide blood to the brain, leading to cell death and potentially lasting disability.
  • Cancer, which can cause cognitive, movement-related, and other kinds of disability when tumors originate in or spread to the brain.
  • Viral or bacterial infection can cause brain inflammation (encephalitis), the symptoms of which can range from flu-like symptoms to severe headache and seizures.
  • Diseases due to developmental defects, such as spina bifida, which involves aberrant development of the spinal column before birth.
  • Seizure disorders, including epilepsy

See more information on Alzheimer’s disease and Dementia, and on Promoting Brain Health.

What are the most common brain diseases?

Stroke and Alzheimer’s disease (along with other dementias) are among the most prevalent neurological conditions, according to recent research. Global studies have reported about 80 million cases of stroke in a single year worldwide and estimated that nearly 44 million people live with Alzheimer’s disease and other dementias. Tension-type headache and migraine, which are classified as brain disorders but not uniformly considered diseases, were the most common conditions identified.

What are some signs of dementia?

Major signs of dementia, which can be caused by Alzheimer’s disease or other diseases, include problems with remembering—which may impede everyday activities (such as completing household tasks or getting to destinations)—and other marked declines in thinking and problem-solving. Some people with dementia also show decreased inhibition, including less control of their emotions. Alzheimer’s diseases and other conditions that cause dementia are progressive: Symptoms may become apparent when they are relatively mild and grow increasingly severe over time.

Brain Injury

Each year, millions of people suffer a sudden blow, jolt, or other impact that impairs the function of their brain. A majority of these brain injuries would be classified as “mild,” resulting in temporary effects on brain function and requiring mostly rest. But more damaging brain injuries can cause extended or permanent difficulties with thinking, communicating, emotion, sensation, movement, and can also be fatal.

Spinal cord injuries, of which there are hundreds of thousands a year, can also have a major impact on nervous system function by damaging the bridge between the brain and the rest of the body. Depending on the severity of the injury, the long-term impact may include partial or total impairment of motor or sensory function below the location of the injury.

For more information, see Traumatic Brain Injury.

What are common causes of brain injury?

Brain injuries occur when a person’s head is struck or jolted, or when it is penetrated by an object (such as a weapon). Common causes of a traumatic brain injury include falls, car accidents, hitting one’s head while playing a sport, and physical assault. Falls are the most common cause of TBI in older adults, while motor vehicle crashes are the biggest cause in young adults. A concussion is a type of brain injury resulting from an impact to the head or body that causes rapid movement of the brain within the skull.

What are some signs of a brain injury?

The signs and symptoms of a brain injury depend on its severity. A mild traumatic brain injury may include symptoms such as headache, dizziness, ringing in the ears, difficulty with memory or focus, blurred vision, or fatigue. In some cases (but not all), someone with a mild TBI will briefly lose consciousness. Those with a more severe TBI may experience a persistent headache, nausea, vomiting, seizures, limb weakness or numbness, slurred speech, agitation, or other symptoms, including those present in mild TBI.

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