Dementia is a loss of brain function that occurs with certain diseases. It affects memory, thinking, language, judgment, and behavior.

Most types of dementia are non reversible (degenerative). Non reversible means the changes in the brain that are causing the dementia cannot be stopped or turned back. Alzheimer's disease is the most common type of dementia.Lewy body disease is a leading cause of dementia in elderly adults. People with this condition have abnormal protein structures in certain areas of the brain.Dementia also can be due to many small strokes. This is called vascular dementia.The following medical conditions also can lead to dementia:

• Parkinson's disease
  
• Multiple sclerosis
  
• Huntington's disease
  
• Pick's disease
  
• Infections that can affect the brain, such as HIV/AIDS and Lyme disease