Parkinson’s disease is characterized as a degenerative disorder of the central nervous system which is understood to persist and continually worsen over time. It is the second most common neurological disorder. Parkinson’s disease affects approximately one million people within the United States. This disorder progresses slowly and is unique in the sense that Parkinson’s disease can be caused by genetics among other things. Parkinson’s disease is well known for its characteristic tremors, stiffness, and difficulty with speech in the patients it affects. Parkinson’s disease is caused by diminishment of the substantia nigra in the tegmentum which controls motor functions within the body. This disease is classified as a basil ganglionic disorder which causes a breakdown of dopamineric neurons in the substancia nigra, located in the midbrain. The substancia nigra is composed of neuromelanin which pigments the substancia nigra and gives it its darker characteristic.
The neuromelanin also connects to the motor cortex which is responsible for one’s motor control and balance. The chemical dopamine is created in the substantia nigra. The basil ganglia receives inputs from the motor cortex, the association cortex, and the substancia nigra. The basil ganglia then sends messages to the motor cortex by way of the thalamus. With Parkinson’s disease, the nigral neurons are damaged, which causes the neuromelanin to be free to move into the adjacent tissue where it is phagocytosed and moved away by macrophages. This degenerative process not only destroys the process of creating dopamine, but it also causes the pigmentation of the substancia nigra to change and become lighter in appearance. The lack of dopamine-related input from the substantia nigra negatively changes the equilibrium of the output from the basil ganglia to the motor cortex. This alteration in the equilibrium then causes the symptoms related to Parkinson’s disease. The direct cause of Parkinson’s disease remains a medical mystery, but many factors can participate in determining whether one is susceptible to developing Parkinson’s disease in the future.
The exposure to specific toxins in the environment and various environmental factors has the possibility of playing a role in those who were diagnosed with Parkinson’s disease. Another possible cause of Parkinson’s disease is the role of one’s genetics. It is found that certain mutations can give rise to Parkinson’s disease, although this is uncommon. The brains of patients with Parkinson’s disease change as the disease progresses. Lewy bodies are microscopic markers that characterize the presence of Parkinson’s disease within a patient. They are abnormal microscopic protein deposits that form in the brain and play a role in disrupting the brain’s normal functions. This disruption causes deterioration. Lewy bodies contain A-synuclein which is a protein that cells cannot break down. Early indicators of Parkinson’s disease include tremors or shaking which can reside in one’s finger, thumb, hand, lip, or chin, though shaking is normal after extensive physical activity, injury, or may be due to medications.
If one’s handwriting begins to appear smaller over a short period of time, it could be a warning sign of Parkinson’s although one should not base their self-diagnosis upon handwriting, for handwriting can change as one advances in age, but this happens over time and not suddenly. A loss of smell in specific foods can be an indicator, but a loss of smell can also be related to the possession of the common cold or the flu. Another early sign may be sudden movements while sleeping such as falling out of the bed or kicking and punching. It is important to understand that people on occasion may experience difficulty sleeping. Chronic stiffness can be a sign, but this symptom can also be caused by an injury or arthritis. If one is experiencing constipation on a daily basis, this can be considered a sign of Parkinson’s disease, although a lack of fiber in one’s diet or medications can determine the moving of one’s bowels. Having recently possessed a soft or low voice is an indicator unless one has a chest cold or other virus.
If one has the appearance of a masked face, a blank stare that persists, or undergoes a long duration of time without the action of blinking, these may be precursors to having Parkinson’s disease. Feeling dizzy or fainting can be signs of low blood pressure and may be connected to Parkinson’s disease along with the inability to stand up straight. There are many Parkinson’s-related symptoms that are known today. The most obvious of symptoms is a resting tremor. A shaking, or tremor, normally starts in one’s limb, and it is often located on a hand or fingers. This resting tremor usually stops when the patient is voluntarily moving the limb affected by the tremor. A “pill-rolling” tremor is common and is characterized by one rolling one’s thumb and forefinger. These tremors can be noticed when the limb is even at a relaxed state. Due to the tremors and inability to control certain motor functions, writing can become difficult for patients with Parkinson’s disease. It is noted that when writing, those effected with Parkinson’s disease posses handwriting that is characteristically small.
Bradykinesia, or a slowing of movement, can be present. Parkinson’s disease has the ability to cause one to move slower which can make simple every-day tasks a challenge. With bradykinesia, one’s steps may become smaller in distance when being mobile, and one’s feet may begin to drag when walking. Excessive muscle tone or hypertonia may be prevalent in patients with Parkinson’s disease and will manifest itself as stiffness or rigidness which causes pain and a loss in one’s range of motion. Parkinson’s disease patients may experience posture impairment and balance, for a patient’s posture can become stooped, and balance can be lost. Patients diagnosed with Parkinson’s disease may experience a loss in their autonomic functions which include and are not limited to smiling, swinging one’s arms while walking, and blinking. This loss in autonomic function caused a select number of patients to stop using their hands while speaking in normal conversations. Speech changes can affect those living with Parkinson’s disease. One may speak out of rhythm in such a way that it may sound soft, quick, hesitant, monotone or slurred.
Diagnosing Parkinson’s disease is not a simple process, for a test for Parkinson’s disease does not yet exist. In order to be diagnosed with Parkinson’s disease, a neurologist must first obtain a detailed medical history of the patient being diagnosed, a review of the patient’s signs and symptoms, a physical examination, and a neurological examination. Tests to exclude other conditions may be ordered to ensure proper diagnosis of the disorder. Once a patient has undergone sufficient testing and examining, the doctor may prescribe the patient the medication carbidopa-levodopa, which is a Parkinson’s disease medicine. If the patient improves considerably while on the medication, this often confirms a Parkinson’s disease diagnosis. There exists a wide-range of treatments for patients that suffer from Parkinson’s disease from drug treatments to surgical treatments.
The pharmacologic approach for those with Parkinson’s disease aims to increase the lack of dopamine in the patient’s basil ganglia. L-dopa or Levodopa is a drug that can cross the blood-brain barrier. The brain can convert this drug to dopamine. Carbidopa can also be prescribed to patients afflicted with Parkinson’s disease. Carbidopa is a decarboxylase inhibitor and, when taken with levodopa, can aid levodopa from converting to dopamine outside of the brain. The combination of medications allows for more levodopa to reach the brain which ultimately increases the brain’s supply of dopamine. These two medications decrease the side effects which are caused by an increased amount of dopamine outside of the brain. They reduce the supply of “free” dopamine from residing outside of the brain. An excess of dopamine outside of the brain could result in low blood pressure, vomiting, and nausea. Other medications include dopamine agonists which directly stimulate nerve receptors inside of the brain which are usually stimulated by dopamine.
In contrast to the medication levodopa, dopamine agonists do not convert into dopamine but rather behave like dopamine. Dopamine agonists are utilized in patients that are in the early stages of Parkinson’s disease and may be added to a treatment plan along with levodopa in the later stages of Parkinson’s disease. It may also be added when levodopa alone cannot sufficiently manage the patient’s symptoms or when the patient has severe motor fluctuations. Side effects associated with levodopa-carbidopa include dizziness upon rising, confusion, nausea, movement disorders, and hallucinations. Side effects commonly associated with dopamine agonists are vomiting, nausea, and orthostatic hypotension. Surgical treatment options are available for those who suffer from Parkinson’s. These surgical treatments are intended to control symptoms related to Parkinson’s disease patients who do not positively respond to medications. One of the surgical treatments creates a lesion in specific portions of the thalamus within the midbrain which become overactive in Parkinson’s disease. A reversible procedure that can be used on patients diagnosed with Parkinson’s disease is deep brain stimulation, or DBS. With this procedure, electrodes are implanted into exact locations. These locations are treated then with pulses of electrical currents.
Why deep brain stimulation works is unknown. Medical experts believe that the current could be activating, affecting, or inhibiting synaptic transmission onto neurons in the vicinity of the electrodes. The future prospects for a cure for Parkinson’s disease are promising, for the medical community has begun to identify the genetic causes linked to Parkinson’s disease. This allows the medical community to expand animal models of Parkinson’s disease. These will be highly useful in the process of understanding the pathogenesis of the disease and will be useful in further testing the neuroprotective therapies which can potentially aid in the fight against the progression of Parkinson’s disease. A different potential approach in the future would be to engage in the replacement of lost neurons via transplantation, which would be highly difficult and tedious. Overall, Parkinson’s disease is well on the way to being better understood and through this understanding scientists will be able to directly identify the source of this disease and eventually find a method that directly cures this disease.
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