In 1817, James Parkinson published his famous treatise: "An Essay on the Shaking Palsy," describing the symptoms which now collectively bear his name. Although many scientists before his time had described various aspects of motor dysfunction (ataxia, paralysis, tremor) Parkinson was the first to collect them into a common syndrome; one which he believed formed a distinctive condition. His sixty-six page essay contained five chapters describing symptoms, differential diagnoses, causality, possible treatments, and prospects for future study. What is most intriguing concerning Parkinson’s analysis (besides its consistent accuracy) is the fact that his clinical observations and inferences were made by watching the movements of six elderly males at a distance along the streets of London.
The symptoms seen in Parkinson’s Disease (PD) are of two distinct types: (1) a degeneration of normal actions and movements coupled with; (2) the appearance of abnormal-type behaviors. Positive symptoms are those behaviors not usually seen in normal people; since they occur often in patients with PD, they are thought to be mechanistically inhibited by normal physiological systems. However, when these systems degenerate or become damaged, they are released and abnormal behavior is the result. The main abnormalities seen in Parkinsonian patients are resting tremor, muscular rigidity, and anesthesia. Resting tremors occur while the patient is motionless; the symptoms disappear during activity or when the patient is asleep. They most often encompass alternating movements of the limbs, hands and head; for instance, one diagnostic tremor known as "pill-rolling," consists of repetitive rolling motions of the forefinger past the thumb. Other involuntary movements include postural changes which are made either as a response to inhibit tremor and muscle stiffness, or attempted unconsciously, without any apparent explanation (the latter is usually the case). These simple movements are referred to as akathesia and can occur during inactivity as well as with motion. Muscular rigidity, on the other hand, reveals an increase in tonicity of both flexors and extensors, especially in the distal limbs. Resistance to movement is seen to a point. However, if sufficient force is used, the muscles give and movement occurs briefly over a short distance. Rigidity is then re-initiated after the movement has stopped. This form of stepwise motions is referred to as cogwheel rigidity; its severity is variable depending on localization of the lesion, extent of neural damage, and progression of the disease over time. It is culminated by an increased slowness with difficulty beginning and continuing most every kind of movement.
Negative symptoms are not indicative of abnormal movements or actions. Rather, they are classified as revealing an absence or inability to perform certain behaviors. Such disorders fall into particular categories based on the type of...