By Irving M. Asher, MD
Parkison's disease (PD) is the second most common neurodegenerative disorder, afflicting more than 1 million people in the United States. The disease usually manifests itself in three main symptoms: (1) bradykinesia — diminished amount of spontaneous movement, or slowness of movement, (2) rigidity — a stiffness of muscles, and (3) resting tremor. These are caused by the loss of a chemical neurotransmitter called dopamine contained in brain cells that project from the substantia nigra in the brainstem to the striatum in the forebrain.
In the 1960’s it was shown that orally administered L-DOPA, a precursor of dopamine, increased the amount of dopamine in the striatum and improved the symptoms of PD, marking a major advance in medical therapeutics for which Arvid Caarlson was awarded the Nobel Prize in 2000. The subsequent development of dopamine agonists that mimic the effect of dopamine in the brain, as well as drugs to prolong the effect of L-DOPA, further improved the ability of physicians to manage the basic motor difficulties associated with PD.
Over the past two decades, it has become apparent that motor impairment and lack of dopamine are only a part of PD, which has been shown to involve changes in many areas of the brain as well as the peripheral autonomic nervous system, which controls blood pressure, heart rate, sweating, and other involuntary functions, and the network of nerves that serves the gut. These widespread pathologic changes result in a diverse complex of symptoms affecting many aspects of the PD patient’s life. Sleep is often fragmented and daytime sleepiness a common problem. Enactment of violent dreams (REM Behavior Disorder) occurs in over 50 percent of PD patients and sometimes precedes the appearance of motor symptoms by up to two decades. Loss of smell and chronic constipation represent other common difficulties that may precede problems with movement. Bladder dysfunction with urgency and the need for frequent urination at night are major contributors to diminished quality of life. Patients with PD commonly experience depression and anxiety as an integral part of their disease. Fatigue and dizzy spells as a result of sudden drops in blood pressure are common in PD. In later stages of PD, dementia, psychosis and imbalance with falls can have major impacts on the life of the PD patient and those caring for them.
The American Academy of Neurology has recently issued guidelines for the care of the PD patient, developed as a result of this new understanding of PD as a multisystemic disorder with a wide range of symptoms, only a fraction of which are related to dopamine deficiency and limitations of motor function. Appreciation of the many and diverse manifestations of PD by physicians and patients alike will allow for improved care and further improve the quality of life of those affected by this disorder.
Published September 25, 2012.
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This is a summary of the article "New Perspectives in the Care of Parkinson's Disease" by Irving M. Asher, MD, which was originally published in the July/August issue of Missouri Medicine. The full article is available here.