Parkinson's disease (PD) is caused by a loss of nerve cells in a part of the brain called the substantia nigra.
This leads to a reduction of dopamine, a chemical that acts as a messenger between the brain and nervous system to control and coordinate body movements, resulting in slow and abnormal movements.
The causes of this loss of nerve cells are unknown.
Currently, they are believed to be a combination of genetic and environmental factors.
PD can occur in families, but it is rare for it to be inherited in this manner.
There is inconclusive evidence that pesticides and herbicides, as well as traffic and industrial pollution, may contribute to PD.
Other causes include medicines like anti-psychotics, stroke and other brain conditions.
The loss of nerve cells is a slow process, with symptoms beginning to develop when about half of the nerve cell activity in the substantia nigra have already been lost.
PD is the second most common neurogenerative disease after Alzheimer’s disease.
There are an estimated 20,000 PD sufferers in Malaysia, with an estimated five-fold increase in the next two decades.
Most PD sufferers develop symptoms when they are more than 50 years of age, although some have developed it before they are 40.
Men are more likely to get PD.
No specific test
There is no specific diagnostic test for PD.
The diagnosis is made on the basis of the complaints, medical history and physical examination.
Diagnosis in the early stages of PD may be difficult because the symptoms are usually mild.
Referrals may be made to a neurologist, who is a medical specialist in conditions affecting the nervous system, or a geriatrician, who is a medical specialist in conditions affecting senior citizens.
The specialist will carry out an assessment to determine if there are problems with movement.
The severity of PD will also be staged with a rating scale.
Imaging investigations may be carried out in some cases to rule out other causes of the symptoms.
Supportive treatment only
There is currently no cure for PD, but there are treatments to relieve the symptoms and maintain quality of life for the patient.
Treatment may not be needed in the early stages of PD as the symptoms are usually mild.
Regular assessments by the specialist are needed to monitor the progress of the disease.
The treatments of PD are both pharmacological and non-pharmacological.
The latter include supportive therapies and surgery for some sufferers.
The supportive therapies are multidisciplinary.
Physiotherapy helps to relieve muscle stiffness, make movement easier, improve walking and flexibility, and improve fitness and ability to manage daily activities.
Occupational therapy helps in providing solutions to accomplishing activities of daily living and ensuring independence for as long as possible.
Speech and language therapy can improve speaking and swallowing. Assistive technology, when available, may also help.
Dietary advice can reduce constipation, unintentional weight loss and reduce dizziness.
Surgery may reduce the symptoms in certain individuals.
These specific types of surgery are only available in certain specialist centres.
The surgeon will discuss the risks and benefits of the procedure with the patient if surgery is being considered.
Additional symptoms, such as depression, anxiety, insomnia, erectile dysfunction, excessive sweating, swallowing difficulties, excessive drooling, urinary incontinence and dementia, need to be treated as well.
Pharmacological options
Medicines can improve tremors and movements.
They are usually prescribed when the symptoms become troublesome.
However, some specialists prescribe them upon diagnosis of PD as it is believed that they will lead to better outcomes.
The three commonly prescribed medicines are levodopa, dopamine agonists and monoamine oxidase inhibitors.
The side effects of the medicines are different.
A “start low, go slow” approach may minimise certain side effects.
However, not all medicines are useful for every PD sufferer.
Levodopa is an effective PD medicine.
It is converted in the brain to dopamine, which usually improves movement problems.
It is often combined with other medicines to prevent its breakdown in the bloodstream before it gets to the brain, and to reduce its side effects, which include nausea, vomiting, tiredness and dizziness.
The dose may need to be increased with time as more nerve cells in the brain are lost.
Dopamine agonists are a substitute for dopamine in the brain with similar, but milder, effects than levodopa.
Sometimes, it is prescribed together with levodopa to reduce the dose of the latter.
Its side effects include nausea, vomiting, dizziness, hallucinations and increased confusion.
It has also been associated in certain individuals with the development of compulsive behaviours, e.g. shopping, gambling and interest in sex.
An uncommon side effect is sudden onset of sleep.
There are different dopamine agonists.
If one causes side effects, another can be substituted.
Monoamine oxidase-B (MAO-B) inhibitors block the breakdown of dopamine by MAO-B, thereby increasing dopamine levels.
Both selegiline and rasagiline, which are MAO-B inhibitors, improve PD symptoms, but their effects are small.
They may be prescribed together with levodopa or dopamine agonists.
Their side effects are occasional and include nausea, headache, abdominal pain and blood pressure changes.
Other medicines prescribed in PD include anti-cholinergic agents, catechol-O-methyltransferase inhibitors, morphine, co-careldopa and foslevodopa-foscarbidopa.
Healthy habits help control
Most PD sufferers can expect to have relatively mild symptoms for some time.
When the symptoms worsen, they can expect several years of good or reasonable control of the symptoms with medicines.
As everyone is different, it is difficult to predict how rapidly PD will progress.
Some may only be disabled two decades after PD first begins, while others may be very disabled after one decade.
There are several interventions that PD sufferers can take to mitigate its effects and maintain a good or reasonable quality of life.
Everyone would benefit from a healthy lifestyle, which includes a healthy diet, maintaining an appropriate weight, regular exercise, sufficient rest, safe sexual practices, avoiding nicotine exposure, moderate alcohol consumption and keeping vaccinations current.
Exercise has been shown to improve many PD symptoms, including balance, mobility, depression, constipation, and even thinking skills.
In addition, there is accumulating evidence that exercise may have a neuroprotective effect, slowing the degeneration of brain cells.
Support groups can also play an important role in helping patients cope with their disease.
The Malaysian Parkinson’s Disease Association (www.mpda.org.my) is a local support group.
Other support groups include the United States-based Parkinson’s Foundation (www.parkinson.org) and the Parkinson Society of Singapore (parkinson.org.sg).
Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. For more information, email starhealth@thestar.com.my. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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