People who have Parkinson's disease may not realize it, as many of the symptoms can mimic other conditions or may be dismissed as normal aging. Some of the most common symptoms of Parkinson's disease include tremors, movement problems, and a fixed facial expression. Although there is extensive, ongoing research involving this disease, there is currently no known cause of the condition and no known cure. However, researchers have discovered that people who have Parkinson's disease have a deficiency of a certain brain chemical (dopamine), which is responsible for movement. Treatment options for this condition can include medications, lifestyle changes, and surgery.