a slowly progressive disease usually occurring in later life, characterized pathologically by degeneration within the nuclear masses of the extrapyramidal system, and clinically by a masklike face (
parkinson's facies), a characteristic tremor of resting muscles, a slowing of voluntary movements, a
festinating gait, peculiar posture, and muscular weakness. Called also
paralysis agitans and
shaking palsy. When the symptom complex occurs secondarily to another disorder, the condition is called
parkinsonism.
Symptoms. Parkinson's disease usually appears gradually and progresses slowly. At first the victim may be troubled by “resting tremors” of the hands and feet that diminish or disappear when the patient begins to move. Hypokinesia (reduced movement) is the most disabling feature of Parkinson's disease. A minor feeling of sluggishness may progress to inability to get up from a chair or even change position in bed. However, once the patient gets into motion, prolonged walking is possible. The gait is shuffling and festinating as the person attempts to regain his center of gravity. Rigidity of muscles in the arms, legs, and face is due to an increase in the tone of skeletal muscles. Loss of mobility in the face produces the characteristic masklike expression. Parkinson's disease does not adversely affect mental capacity.
Treatment. In general, treatment is symptomatic, supportive, and palliative. Most patients require lifelong management consisting of drug therapy, supportive psychotherapy, physical therapy, and rarely, surgical intervention. Newer forms of treatment now give hope for freedom from the progressive disability that once was almost inevitable. The biochemical basis of parkinsonism is a loss or inhibition of
dopamine activity in the corpus striatum, resulting from degeneration of the dopaminergic nigrostriatal pathway. Normally, the two opposing neurotransmitters in this structure,
dopamine and
acetylcholine, are in balance. When dopamine is depleted, the functional overactivity of acetylcholine produces the symptoms of parkinsonism.
In patients with mild symptoms and little functional impairment, some relief from symptoms can be obtained with anticholinergic
agents, such as
trihexyphenidyl (
Artane), or with
antihistamines with
anticholinergic properties, such as
diphenhydramine (
Benadryl). These drugs block the muscarinic effects of
acetylcholine in the central nervous system. Tricyclic
antidepressants, such as
imipramine or
amitriptyline, are also effective; they block the reuptake of
dopamine from nerve synapses and also have anticholinergic effects.
In patients with more severe symptoms and difficulty with routine daily activities, it is necessary to augment the dopamine level in the brain. This is done by administering
levodopa, which crosses the blood-brain barrier and is converted to dopamine by decarboxylation. This reaction also occurs in the peripheral tissues, and the dopamine produced may cause side effects such as cardiac stimulation (tachycardia and arrhythmias) and also nausea and vomiting. A newer drug called
Sinemet, which combines
carbidopa with
levodopa, is now being used to counteract the undesirable effects that may occur when levodopa is used alone. Carbidopa inhibits production of dopamine outside the brain, thus allowing more effective relief of symptoms. A disadvantage to the combination drug is that in some patients it may have only a limited span of effectiveness; therefore, it is usually reserved for more severe cases.
Patients receiving levodopa alone or in combination with carbidopa require nutritional counseling because dietary habits can greatly affect the action of the drug. Protein intake requires special attention because levodopa, an amino acid, must compete with the dietary amino acids for transport through the intestinal epithelium and across the blood-brain barrier. Alcohol intake also must be limited because in large amounts it can antagonize the effects of dopamine. Although the newer combined form of medication offers relief to many persons with Parkinson's disease, it must be given with caution and under continued supervision. Fewer than 10 per cent of patients with Parkinson's fail to respond to some combination of individual drugs.
Patient Care. Since these patients' mental outlook and motivation can affect the extent to which they can successfully cope with their disability, it is important that they receive psychological support. They should know the nature of the disease affecting them and be given realistic hopes for forestalling or preventing its more serious effects.
Some benefits can be derived from physical therapy in the form of applications of heat and massage to alleviate muscle cramps and relieve the tension headaches that often accompany rigidity of the cervical muscles. The patient also is instructed in simple exercises to perform at home. Although depression often accompanies the physical limitations of Parkinson's disease, much psychological benefit can be derived from maintaining mobility and observing social and emotional ties. Patients can be taught to initiate walking by leaning forward to stimulate intact walking reflexes. Family members will need help in dealing with the patient's slowness of speech and communication difficulties. Some minor changes in the home, such as railings and support bars, can encourage independent movement.