Dementia refers to a loss of cognitive function (cognition) due changes in the brain caused by disease or trauma.  The changes may occur gradually or quickly; and how they occur may determine whether dementia is reversible or irreversible. 

Cognition is the act or process of thinking, perceiving, and learning.  Cognitive functions that may be affected by dementia include the following:

• Decision making, judgment
• Memory
• Spatial orientation (knowing where they are)
• Thinking, reasoning
• Verbal communication

Dementia also may result in behavioral and personality changes, depending on the area(s) of the brain.

1. Some dementia is reversible and can be cured partially or completely with treatment.  The degree of reversibility often depends on how quickly the underlying cause is treated.

2. Irreversible dementia is caused by an incurable condition (e.g., Alzheimer’s disease).  Patients with irreversible dementia are eventually unable to care for themselves and may require round – the – clock care.

(Source: Neurology Channel - http://www.neurologychannel.com)