Parkinson's disease
Parkinson's disease: Excerpt from Professional Guide to Diseases (Eighth Edition)
Named for James Parkinson, the English physician who wrote the first accurate description of the disease in 1817, Parkinson’s disease characteristically produces progressive muscle rigidity, akinesia, involuntary tremor, and dementia. Death may result from aspiration pneumonia or an infection.
Causes and incidence
Although the cause of Parkinson’s disease is unknown, study of the extrapyramidal brain nuclei (corpus striatum, globus pallidus, and substantia nigra) has established that a dopamine deficiency prevents affected brain cells from performing their normal inhibitory function within the central nervous system. Parkinson’s disease occurs in families in some cases; in others, it’s secondary to external factors such as medications used to treat schizophrenia.
Parkinson’s disease, also called parkinsonism, paralysis agitans, and shaking palsy, is one of the most common crippling diseases in the United States. Parkinson’s disease strikes 2 in every 1,000 people, most often developing in those older than age 50; however, it also occurs in children and young adults. Because of increased longevity, this amounts to roughly 60,000 new cases diagnosed annually in the United States alone. Incidence increases in persons with repeated brain injury, including professional athletes, and persons using psychoactive substances, whether prescribed or illicit.
Signs and symptoms
The cardinal symptoms of Parkinson’s disease are muscle rigidity and akinesia and an insidious resting tremor that begins in the fingers (unilateral pill-roll tremor), increases during stress or anxiety, and decreases with purposeful movement and sleep. Muscle rigidity results in resistance to passive muscle stretching, which may be uniform (lead-pipe rigidity) or jerky (cogwheel rigidity). Akinesia causes the patient to walk with difficulty (gait lacks normal parallel motion and may be retropulsive or propulsive) and produces a high-pitched, monotone voice; drooling; a masklike facial expression; loss of posture control (the patient walks with body bent forward); and dysarthria, dysphagia, or both. Occasionally, akinesia may also cause oculogyric crises (eyes are fixed upward, with involuntary tonic movements) or blepharospasm (eyelids are completely closed). Parkinson’s disease itself doesn’t impair the intellect, but a coexisting disorder, such as arteriosclerosis, may do so.
Diagnosis
Generally, laboratory data are of little value in identifying Parkinson’s disease; consequently, diagnosis is based on the patient’s age, history, and characteristic clinical picture.
Conclusive diagnosis is possible only after ruling out other causes of tremor, involutional depression, cerebral arteriosclerosis and, in patients younger than age 30, intracranial tumors, Wilson’s disease, or phenothiazine or other drug toxicity.
Treatment
Because Parkinson’s disease has no cure, the primary aim of treatment is to relieve symptoms and keep the patient functional as long as possible. Treatment consists of drugs, physical therapy and, in severe disease states unresponsive to drugs, stereotactic neurosurgery or the controversial treatment called fetal cell transplantation. In this treatment, fetal brain tissue is injected into the patient’s brain. If the injected cells grow within the recipient’s brain, they will allow the brain to process dopamine, thereby either halting or reversing disease progression. Neurotransplantation techniques, including the use of nerve cells from other parts of the patient’s body, have been attempted with varying results.
Drug therapy usually includes levodopa, a dopamine replacement that’s most effective during early stages. It’s given in increasing doses until symptoms are relieved or adverse effects appear. Because adverse effects can be serious, levodopa is frequently given in combination with carbidopa to halt peripheral dopamine synthesis. Occasionally, levodopa proves ineffective, producing dangerous adverse effects that include postural hypotension, hallucinations, and increased libido leading to inappropriate sexual behavior. In that case, alternative drug therapy includes anticholinergics such as trihexyphenidyl, antihistamines such as diphenhydramine, and amantadine, an antiviral agent.
Research on the oxidative stress theory has caused a controversy in drug therapy for Parkinson’s disease. Traditionally, levodopa-carbidopa has been a first-line drug in management; however, it has also been associated with an acceleration of disease process. Inclusion of entacapone potentiates the effects of levodopa-carbidopa treatment so that less frequent doses are required.
Selegiline, an enzyme-inhibiting agent, allows conservation of dopamine and enhances the therapeutic effect of levodopa. Selegiline used with tocopherols delays the time when the patient with Parkinson’s disease becomes disabled.
ELDER TIP Elderly patients may need smaller doses of antiparkinsonian drugs because of reduced tolerance. Be alert for and report orthostatic hypotension, irregular pulse, blepharospasm, and anxiety or confusion.
When drug therapy fails, stereotactic neurosurgery, such as subthalamotomy and pallidotomy, may be an alternative. In these procedures, electrical coagulation, freezing, radioactivity, or ultrasound destroys the ventrolateral nucleus of the thalamus to prevent involuntary movement. This is most effective in young, otherwise healthy people with unilateral tremor or muscle rigidity. Neurosurgery can only relieve symptoms. Brain stimulator implantation alters the activity of the area where Parkinson’s disease symptoms originate. A pacemaker is implanted into the chest wall, and the electrode is threaded (using magnetic resonance imaging for guidance) to the thalamus, pallidum, or subthalamic nucleus. A successful procedure reduces the need for medication, thus reducing the medication-related adverse effects experienced by the patient.
Individually planned physical therapy complements drug treatment and neurosurgery to maintain normal muscle tone and function. Appropriate physical therapy includes both active and passive range-of-motion exercises, routine daily activities, walking, and baths and massage to help relax muscles.
Special considerations
Effectively caring for the patient with Parkinson’s disease requires careful monitoring of drug treatment, emphasis on teaching self-reliance, and generous psychological support.
❑Monitor drug treatment and adjust dosage, if necessary, to minimize adverse effects.
❑If the patient has surgery, watch for signs of hemorrhage and increased intracranial pressure by frequently checking level of consciousness and vital signs.
❑Encourage independence. The patient with excessive tremor may achieve partial control of his body by sitting on a chair and using its arms to steady himself. Advise the patient to change position slowly and dangle his legs before getting out of bed. Remember that fatigue may cause him to depend more on others.
❑Help the patient overcome problems related to eating and elimination. For example, if he has difficulty eating, offer supplementary or small, frequent meals to increase caloric intake. Help establish a regular bowel routine by encouraging him to drink at least 2 qt (2 L) of liquids daily and eat high-fiber foods. He may need an elevated toilet seat to assist him from a standing to a sitting position.
❑Give the patient and his family emotional support. Teach them about the disease, its progressive stages, and drug adverse effects. Show the family how to prevent pressure ulcers and contractures by proper positioning. Inform them of the dietary restrictions levodopa imposes, and explain household safety measures to prevent accidents. Help the patient and his family express their feelings and frustrations about the progressively debilitating effects of the disease. Establish long- and short-term treatment goals, and be aware of the patient’s need for intellectual stimulation and diversion. Refer the patient and his family to the National Parkinson Foundation or the United Parkinson Foundation for more information.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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