Delirium is the condition of abrupt mental confusion or significant lost of mental awareness.  This condition can be caused by various factors including lack of blood flow to the brain, exhaustion, dehydration, drug influence, and lack of sleep.  Delirium is usually temporary and most often exhibited by the elderly.  More serious cases of delirium may be the result of physical damage of the brain from strokes or underlying diseases, such as multiple sclerosis and Parkinson’s disease.