Parkinson's Disease - Overview, Causes, Clinical features and Diagnosis

Parkinson's disease (PD) is a long-term degenerative disease of the central nervous system that mainly affects the motor system. The symptoms generally come on slowly over time. Put more simply, it is a medical condition in which parts of the brain become progressively damaged over many years. Symptoms of Parkinson's disease include muscle rigidity, tremors (or shaking), and changes in speech and gait.

Parkinson’s causes are unknown but genetics, aging (as it mostly affects older people), and toxins are being researched. After a Parkinson’s diagnosis, Parkinson’s disease treatments are given to help relieve symptoms. There is no cure for Parkinson's and herbal remedies are not shown nor proven to be of any benefit. Studies on using stem cells to treat Parkinson's disease are under way. The prognosis depends on the patient's age and symptoms. Now let us look at PD in more detail.

What is Parkinson's disease?

As defined above, Parkinson's disease is a condition in which parts of the brain become progressively damaged over many years. PD affects the way you move. It happens when there is a problem with certain nerve cells in the brain. Normally, these nerve cells make an important chemical called dopamine. Dopamine sends signals to the part of your brain that controls movement. It lets your muscles move smoothly and do what you want them to do. When you have Parkinson’s, these nerve cells break down. Then you no longer have enough dopamine, and you have trouble moving the way you want to.

Parkinson’s disease typically begins after the age of 50. The disease can be very hard to live with because it severely restricts mobility and as a result makes daily activities increasingly difficult. Parkinson’s disease is progressive, which means it gets worse over time. But usually this happens slowly, over a period of many years. And there are good treatments that can help you live a full life.

What causes Parkinson's disease?

The fundamental problem is a loss of nerve cells in part of the brain called the substantia nigra. This leads to a reduction in the chemical called dopamine usually found in the brain, as already explained above. Dopamine plays a vital role in regulating the movement of the body. A reduction in dopamine is responsible for many of the symptoms of Parkinson's disease.

No one knows for sure what makes these nerve cells break down in the first place. Most experts think that a combination of genetic and environmental factors is responsible. Medical scientists are doing a lot of research to look for the answer. They are studying many possible causes, including aging and poisons in the environment. Abnormal genes seem to lead to Parkinson's disease in some people. But so far, there is not enough proof to show that it is always inherited.

What are the symptoms?

The three main symptoms of Parkinson's disease are:

involuntary shaking or trembling of particular parts of the body when at rest (resting tremor). Tremor may affect your hands, arms, legs, or head.
slow movement (akinesia)
stiff and inflexible muscles (muscle rigidity) - in many cases, causing problems with balance or walking.

A person with Parkinson's disease can also experience a wide range of other physical and psychological symptoms, including:

depression and anxiety
balance problems – this may increase the chance of a fall
loss of sense of smell (anosmis)
problems sleeping (insomnia)
memory problems

Tremor may be the first symptom you notice. It is one of the most common signs of the disease, although not everyone has it. More importantly, not everyone with a tremor has Parkinson's disease. Tremor often starts in just one arm or leg or only on one side of the body. It may be worse when you are awake but not moving the affected arm or leg. It may get better when you move the limb or you are asleep. This type of tremor is called resting tremor.

In time, Parkinson’s affects muscles all through your body, so it can lead to problems like trouble swallowing or constipation. In the later stages of the disease, a person with Parkinson’s may have a fixed or blank expression, trouble speaking, and other problems. Some people also have a decrease in mental skills (dementia).

People usually start to have symptoms between the ages of 50 and 60, but in some people symptoms start earlier.

How is Parkinson's disease diagnosed?

Your GP or doctor will ask questions about your symptoms and your past health and will do a neurological exam. If he suspects you have PD, you may be referred to a specialist. This will usually be either a neurologist – a specialist in conditions affecting the brain and nervous system; or a geriatrician – a specialist in problems affecting elderly people.

A neurological exam includes questions and tests that show how well your nerves are working. For example, your doctor or the specialist will watch how you move, check your muscle strength and reflexes, and check your vision. In some cases, he or she may have you try a medicine. How this medicine works may help your doctor or the specialist know if you have Parkinson's disease. He or she will also ask questions about your mood.

There are no laboratory or blood tests that can conclusively show your doctor or the specialist (i.e. neurologist or geriatrician) whether you have Parkinson’s or not. A diagnosis of Parkinson's disease is likely if you have at least two of the three following symptoms:

shaking or tremor in a part of your body that usually only occurs at rest
slowness of movement (bradykinesia)
muscle stiffness (rigidity)

If your symptoms improve after taking a medication called levodopa, it's more likely you have Parkinson's disease. But you may have tests to help rule out other diseases that could be causing your symptoms. For example, you might have an MRI to look for signs of a stroke or brain tumor. Special brain scans, such as a single photon emission computed tomography (SPECT) scan, may also be carried out in some cases to try to rule out other causes of your symptoms.

Let us go on to discuss the different treatment modalities currently available for Parkinson's disease.

Treatment »

Reference:
1). NHS Choices: Parkinson's disease. Accessed 01.07.2010. Available here: http://www.nhs.uk/Conditions/Parkinsons-disease/Pages/Introduction.aspx
2). US Library of Medicine (PubMed Health). Parkinson's: Overview. Accessed 12.09.2017. Available here: https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0076679/
3). U.S. Department of Health and Human Services. Parkinson's Disease. Accessed 13.09.2017. Available here: https://www.report.nih.gov/NIHfactsheets/ViewFactSheet.aspx?csid=109

Article first written 01/07/2010. Rewritten 12/09/2017