In Parkinson's disease, or PD, nerve cells die in an area of the brain controlling movement. The primary motor effects of PD vary in degree, ranging from minor movement impairment to severe disability. However, according to the National Parkinson Foundation, the nonmotor effects are becoming the focus of research, since these effects may occur years before the motor effects are noticed.
Genetic Causes
Genes appear to have a connection to PD, reports the National Institute of Neurological Disorders and Stroke. In cases where the disease is prevalent in families, mutation of a specific gene passed from one generation to the next is suspected. However, in most cases, it is thought that genes create a predisposition for the disease. It takes interaction with an environmental trigger to increase the disease potential.
Environmental Causes
According to the National Institute of Neurological Disorders and Stroke, research has consistently linked toxins such as pesticides to PD. Viruses may also play a role. Furthermore, information from The Michael J. Fox Foundation for Parkinson's Research suggests a connection between head injuries--considered environmental events--and people with a predisposition for PD.
Tremor
According to the American Academy of Neurology, the majority of patients develop tremor. The characteristic back and forth shaking of PD often begins in one hand. It is a resting tremor that disappears momentarily with an intentional movement, such as reaching for a cup. Tremor may appear in the jaw, head, arms, legs and body. When it is severe, tremor may inhibit daily activities.
Bradykinesia
The term literally means slow movement. Ordinary tasks such as washing and dressing that were once performed quickly can become an ordeal. Poverty of movement has also been used to describe the decrease in voluntary and spontaneous action. Loss of automatic movements such as blinking and smiling contribute to the fixed, mask-like expression of those with PD.
Rigidity
The resistance to movement is caused by a disruption in the signals from the brain coordinating the contraction and relaxation of opposing muscle groups. The rigidity or stiffness is often referred to as a "cog-wheel" motion. Prolonged muscle tension may cause discomfort and pain.
Postural Instability
Impaired balance increases the risk for falls. Stability may be further compromised by a forward-leaning or stooped posture and a lack of compensatory arm movements.
Gait
Patients may develop a Parkinson's gait typified by short, shuffling steps and a lack of arm swinging. Difficulty initiating walking or abruptly stopping are examples of the "freezing" phenomenon that some patients experience. A hurried or festinating gait describes the action of walking slowly initially but then progressively accelerating with little control.
Non-motor Effects
Cognitive and autonomic nervous system dysfunctions account for most of the non-motor effects. Memory, language and reasoning are among the intellectual skills affected. Examples of autonomic nervous system disturbances are sleep disorders, bowel and bladder dysfunction, and speech and swallowing difficulties. Areas of the brain responsible for mood and emotions may also be compromised, leading to depression, anxiety and personality changes.
References
- National Parkinson Foundation: What is Parkinson's disease (PD)?
- National Institute of Neurological Disorders and Stroke: Parkinson's Disease: Hope Through Research
- The Michael J. Fox Foundation for Parkinson's Research: What are the risk factors for PD?
- American Academy of Neurology: Parkinson's Disease
