Alex Zhdan
Professor Donnelly
Anatomy 1571
11/11/2017
Parkinson’s Disease
Parkinson’s Disease is a progressive neurological disease that affects thousands across the globe. It is a brain disorder that disturbs many spheres of life including mobility, mood, and autonomic functions. Stemming from neuron degradation within the brain, the disease has troubling implications on physical and cognitive processes. Although no cure is available, there are ways to reduce the risk of this disease as well as treatments that alleviate the symptoms associated with Parkinson’s disease which vary based on age, cognitive function, and response to treatment.
Parkinson’s Disease (PD) manifests itself in the human body through a number of observable ways. Many physical signs stem from the movement control centers of the brain. This includes “tremors, rigidity, slow movements (bradykinesia), and posture instability” (Gulli 824). A person with Parkinson’s Disease slowly begins to lose muscle control in different areas of the body, one of which is the sphincter muscles in the bladder and rectum. This causes urinary and fecal incontinence. Affected people can have urge incontinence where the sensation to urinate comes suddenly, or stress incontinence where the bladder can leak during coughing or laughing (Mosley 139). Tremors start occurring when muscles start to contract and relax involuntarily. Muscle tone may increase which often causes a masklike appearance of the face (Tortora 593). Furthermore, the range of motion decreases due to hypokinemia; walking is impaired, arm swings diminish, writing is more difficult and shaky. Doing everyday tasks such as cutting food, shaving, and buttoning a shirt may take longer to do (Tortora 593). Blurry vision is also a very common issue due to eyelid rigidity and bradykinesia (Mosley 36). The physical manifestations of the disease complicate the lives of the PD patients, leading to falls, depression, and often general dissatisfaction with quality of life.
The overall pathogenesis of Parkinson’s Disease is not very clear. The reasons for the dying motor neurons in the brain are unknown. In fact, about 85% of the cases of Parkinson’s Disease are idiopathic, meaning that there is no obvious cause or explanation (Mosley 139). Genetics is thought to not be an influential factor, with only five percent of patients having a family history of the disease (Tortora 593). However, genetics is currently being actively researched in the scientific community as many emerging cases are starting to show closer links to genetics and certain geographic prevalence. Although the cause is unknown, the functions and components in the brain involved with PD have been identified and studied.
Fundamentally, Parkinson’s Disease stems from a disorder in the basal ganglia, which is the part of the brain that is largely responsible for movement. More specifically, the caudate nucleus and the putamen are responsible for receiving input from motor areas of the cerebral cortex and the substantia nigra. Output then comes from the globus pallidus and substantia nigra (Tortora 588). The disease is precipitated by the degeneration of dopamine releasing neurons that are found in the substantia nigra. The caudate nucleus contains neurons that release acetocholine, but in PD this production does not digress like the dopamine does, which causes for an imbalance in the levels of dopamine and ACh (Tortora 593). It is this imbalance that may be causing the majority of symptoms in PD patients.
Although the cause of PD is unknown, there are several environmental factors that are believed to contribute to PD. Some of these include exposure to chemicals such as pesticides, herbicides, and carbon monoxide (Tortora 593). Genetics, although previously believed to not be closely associated with the disease, has in recent times become a talking point in the scientific community. Genetic research continues to be done and some links have been made between people with the disease and their geographical family origins (Palfreman 170), which will be discussed later. Also, “toxins such as MPTP, an impurity in some illegal drugs, can also cause parkinsonism by generating free radicals in the body. Symptoms of PD appear within hours of ingestion” (Gulli 825). These free radicals can cause cell death. Cell death can also be precipitated by infection, trauma and poisoning. These factors give rise to PD symptoms, although it is unclear whether or not there is a direct link.
The population affected by Parkinson’s Disease is mostly people over the age of 60. “Specifically, about one percent of people over the age of 60 develop PD. It is also 1.5 times more common to see in men than in women” (Gulli 824). In recent years, trends have been rising in the number of people who exhibit symptoms of the disease at age 40 (Mosley 230). About one million Americans are affected by this disease. Each year there are about 50,000 new cases diagnosed (Mosley 225). It is clear that aging is a correlation for this disease- the older a person becomes, the more likely they are to experience PD.
Clinical assessment for the disease is essentially a diagnostic journey. Long term observation may need to be conducted by the primary care physician and neurologist to gauge and diagnose the disease in clinical practice. Physicians must weigh their patients’ full medical histories and conduct neurological exams to see possible symptoms. “Tests for other causes of parkinsonism may include brain scans, blood tests, lumbar puncture, and x rays” (Gulli 826). Mini-Mental Status Evaluations (MMSE) can also be useful ways to gather as much clinical information as possible to attempt a diagnosis.
Unfortunately, no definitive tests exist for this disease. Parkinson’s disease is difficult to diagnose accurately due to the large variety of symptoms. One test that can be done to detect the loss of dopamine neurons is SPECT or single photo emission computed tomography. Radionuclides are injected into the body and computerized imaging techniques can then show the internal brain structures such as the basal ganglia (Mosley 277). The multidimensional images can provide information about existing damage to these areas of the brain.
There is a variety of current treatments available for patients with this progressive degenerative disease. This includes pharmacological treatment and lifestyle alterations. The pharmacological treatments for PD often times target the underlying problem of the disease – unbalanced dopamine levels. The drug levodopa, developed in the 1960s, partially alleviates symptoms by acting as a precursor to dopamine (Tortora 593). However, since the disease is progressive, the drug becomes useless as more brain cells die with time. Anticholinergic drugs can reduce symptoms including tremors and rigidity by restoring the balance between ACh and dopamine. The blood-brain barrier, which is a “dense layer of endothelial cells that line the interior of blood vessels in the brain to form a semipermiable membrane that significantly limits the molecules that can pass from the blood to the brain” (Mosley 35). This poses a challenge to the disease since dopamine and other neurotransmitters cannot be transmitted through the membrane and so dopamine therapies cannot act directly on the involved portions of the brain. Other treatments reflect lifestyle changes that patients can make. For example, regular exercise has been shown to improve motor functions and maintain a more optimal range of motion by those suffering from PD. Furthermore, patients taking levodopa may need to limit their protein intake as levodopa is an amino acid absorbed by the same transporters that pick up amino acids from the proteins found in the patient’s diet (Gulli 826). These changes can help improve overall wellbeing and happiness.
Since there is no cure for Parkinson’s Disease, there is research being done to find a way to reverse the effects of the disease, and eventually to permanently cure it. Certain research demonstrates that PD may originate due to certain environmental factors that have not yet been discovered. One such study examined several families who had descendants from a small village in southern Italy called Contursi. The multi-generational families were examined by geneticists- blood samples were drawn and their DNA was analyzed. The autopsies revealed a large number of “Lewy structures, a pathological hallmark of true Parkinson’s Disease” (Palfreman 157). Geneticists also discovered that the families from this region had a mutation in a specific band of chromosome 4 (Palfreman 161). A 2011 study linked the disease with a gene that codes for a protein called alpha-synuclein (Gulli 823). This discovery provided clues to how the disease spreads within the body, however more research is being done to provide definitive answers on possible treatments.
Another area of research has focuses on antioxidants. Specifically, the only antioxidant that has shown to be a potential treatment is selegiline. Selegiline provides the body with the antioxidant co-enzyme Q10 which is found in every cell of the human body. Supplementation of this co-enzyme showed the ability to slow the progression of PD in preliminary studies (Gulli 827). In fact, there are half a dozen clinical trials in progress as of 2011 to further understand the implications of this promising research.
Surgical procedures are also being researched to treat PD. A highly experimental procedure is the transplant of fetal nigral cells, but these surgeries have only shown modest benefits (Gulli 828). Another procedure is a pallidotomy in which targeted areas of neutrons are destroyed within the globus pallidus. The goal is to interrupt neuronal activity in this structure which controls movement, which in turn reduces symptoms like tremors, rigidity, and dyskinesia (Mosley 219). Overall, multiple types of treatments mentioned can be combined and structured to form a promising silver lining of treatment for those suffering from PD, ultimately improving their quality of life as they grow older.
DBS therapy is another solution being studied and improved to help abate PD symptoms. In this therapy, a small device is placed inside the chest and pulses are then sent to the brain to block nerve signals. “Changes in neurophysiology, neurochemistry, neurovascular structures, and neurogenesis may also underpin the benefits of DBS therapy” (Okun). Although this procedure doesn’t treat all symptoms, it can be used when other forms of treatment have been ineffective.
There are various preventative measures and steps people can take to reduce the risk of PD. Coffee and other caffeinated beverages have been shown to help reduce the likelihood of Parkinson’s Disease. Scientists believe caffeine blocks alpha-adenosine receptor activation in the brain” (Mosley 44). Scientists posit that this extends the effectiveness of dopamine, which is critical for proper body mobility. Smoking tobacco has shown to protect against PD,
All in all, Parkinson’s Disease causes drastic lifestyle changes to people it seizes. Despite no definitive panacea available, there are ways the fight the symptoms associated with this disorder. Until a cure is found, patients must remain hopeful, as did renaissance man and discoverer of Parkinson’s disease, James Parkinson: “There appears to be sufficient reason for hoping that some remedial process may ere long be discovered, by which, at least, the progress of the disease may be stopped.