Parkinsonism is a constellation of symptoms, including rigidity (stiffness), bradykinesia (paucity of spontaneous movement), loss of postural reflexes (prone to getting off balance and falling easily). It occurs in several different disease states, and can also be a side effect of certain medications (mostly used for prevention of nausea and for anti-psychotic uses).
Parkinson's Disease is the most common illness in which Parkinsonism is seen. Tremor is also a common symptom of parkinson's disease, although it is much less common in other diseases which cause Parkinsonism. The tremor is often the first symptom noticed by the patient, and occurs most frequently in the hands and arms, but occasionally in the jaw. The head itself rarely participates in the tremor. The Parkinson's tremor is a resting tremor, meaning it is worse when the limb is at rest and improves when the limb is used for a task. Parkinson's disease is a progressive degenerative disease of the brain. There is no cure at this time, but there are some very effective medical and surgical treatments. The links below contain much useful information about Parkinson's Disease.
Other Parkinsonian
Syndromes include Progressive Supranuclear Palsy, Shy-Drager Syndrome,
and Multi-system Atrophies. Links are given below to these also.
Organizations
There are two US national parkinson service organizations. This one is based in Miami, Florida
American Parkinson Disease Association
This is the other US parkinson service organization, based in New York.
Society for Progressive Supranuclear Palsy
Useful Links
Shy-Drager syndrome is Parkinsonism plus failure of the autonomic system, leading to postural low blood pressure (fainting) and incontinence.