Genetics, environmental factors, and free radicals are some of the possible causes of Parkinson's disease, although the exact cause is not yet known. This chronic and progressive brain disorder causes several symptoms, such as tremors, a fixed facial expression, and movement problems. Researches have discovered that many of the characteristic symptoms of Parkinson's disease occur as the result of a deficiency of a certain brain chemical (dopamine). There is no known cure for this disease, but medications, lifestyle changes, and surgery may help to relieve many of the symptoms of Parkinson's.