Parkinson's diseaseThere is a group of people who live the last years of their lives in glass boxes. They are perfectly able to see outside, but unable to reach the world around them. Their emotions cannot be shown through facial expression, and as their condition continues, even speech becomes difficult or even impossible. These people are men and women of all races and geographic areas, who make up 1% of the world's population over the age of 50. Parkinson's disease is their disease. Although parkinsonism has existed for almost all of history, a cause or cure has not yet been found. Drugs tame symptoms and prolong life, but they cannot reverse the progression of the disease. The diagnosis is based exclusively on clinical signs and symptoms, because almost all laboratory and radiographic tests are normal in Parkinson's patients. For this reason, early diagnosis is very difficult. The fact that early signs of parkinsonism can easily be overlooked as normal aging further complicates the diagnosis. Therefore, primary care physicians of the middle-aged and elderly population must be extremely sensitive to patients' external appearance and changes in movement ability. Most signs and symptoms of Parkinson's disease correspond to one of three motor deficits: bradykinesia, akinesia, tremor, and rigidity. The first two qualities are usually present before the tremor, but often the patient and even the doctor attribute them to aging, so the disease is rarely diagnosed until the tremor becomes evident much later. An average of 80% of nigrostriatal neurons may have already degenerated at the time of diagnosis of parkinsonism, which complicates treatment (Fitzgerald, 130). Bra......half sheet......ed. Bailliere Tindall. London: 1985. Kandel, E. R., J. H. Schwarz, and T. M. Jessel. Principles of neural science. 3rd ed. Elsevier. New York: 1991.Korczyn, A.D. "Autonomic Nervous System Disorders in Parkinson's Disease." Advances in neurology. vol. 53, 1990, Pp., 463-468. Langston, J.W. "Current Theories on the Cause of Parkinson's Disease." Journal of Neurology, Neurosurgery, and Psychiatry. 1989, suppl. , pp. 13-i7.Lees, A.J. "The on-off phenomenon." Journal of Neurology, Neurosurgery and Psychiatry. 1989, suppl. , pp. 29-37. Lieberman, A., "Emerging Perspectives in Parkinson's Disease." Neurology. April 1992. suppl 4.. Pp. 5-7. Rowland, L.P., ed. Merritt Neurology Textbook. 7th ed. Lea and Febiger. Philadelphia: 1984. Walton, Sir John. Diseases of the brain of the nervous system. 9th ed. Oxford University Press. Oxford: 1985.