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What is Parkinson's disease?
Parkinson's Disease (PD) is a gradual, progressive neurological condition classically characterized by a tremor (usually at first in the hand), rigidity and slowness of movement; these symptoms initially occur on one side of the body. The disease becomes more common with age, particularly beyond the age of 60. It can though rarely present much earlier (before the age of 30), which is suggestive of an inherited form of disease.
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What is the cause?
It is thought that PD is the result of both genetic (it does tend to run in families) and environmental factors. With respect to the latter, studies suggest that exposure to certain metals or toxins increases the susceptibility to PD. There is a decreased risk of PD in those who drink coffee and smoke cigarettes. Although the disease process is not completely understood, it is known that there is a decrease in one of the chemicals found in the brain, dopamine. Current treatments are aimed at addressing this deficiency.
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How common is the problem?
Parkinson's disease is thought to affect over six million people worldwide, and is slightly more common in men than in women. Up to 10% of sufferers are diagnosed before the age of 50.
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What are the symptoms?
Of the aforementioned symptoms, mild slowness of movement and rigidity may also be present on the other side of the body at diagnosis. The condition does tend to be more prominent on one side than the other throughout its course. As the disease progresses, the slowness, tremor and rigidity become more pronounced. The patient may also begin to display an impassive expression, a characteristic sign of disease.
There is a greater liability to fall on account of problems with balance. Classically a Parkinson's patient is described as having a slow, 'shuffling' walk. He or she may be seen to 'freeze' (stop suddenly) when turning or passing through a restricted space such as a doorway. Problems with speech, swallowing and drooling are further features of progression.
Other symptoms include the need to urinate frequently+/-incontinence, constipation, problems with sleep and postural hypotension (the tendency to feel dizzy when sitting or standing up, often leading to more falls). 'Cognitive' changes lead to problems with concentration and memory, with almost a third of Parkinson's patients going to develop dementia. -
How is it diagnosed?
The diagnosis continues to be a clinical one. Imaging such as CT scans or MRI do not contribute to the diagnosis, nor are there any blood tests that are helpful.
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What is the treatment?
There is no cure for Parkinson's disease. Treatment at this time is based on addressing the symptoms. There are six types of medication available: anticholinergics, amantidine, L-dopa, dopamine agonists, MAOI (monoamine oxidase inhibitors) and COMT-I (catechol-O-methyltransferase inhibitors).
L-dopa is the precursor of dopamine, the brain chemical deficient in Parkinson's disease. Though still the mainstay of Parkinson's therapy, it is not without its own problems; long-term complications include fluctuations in effectiveness, abnormal movements ('dyskinesias') and psychiatric manifestations such as hallucinations.
It is common practice at this time for younger patients to be tried on dopamine agonists first, on account of the fact that they have shown to delay the onset of early dyskinsias and fluctuations. As they have also been shown to be less effective and less well tolerated than L-dopa, older and less healthy patients are started on L-dopa at the onset. -
What is the role of surgery in Parkinson's disease?
Parkinson's patients with more advanced disease have a poor quality of life, the symptoms exacerbated by side effects of their treatment (notably L-dopa). For some of these patients surgery may be useful in alleviating some of their symptoms.
Examples of procedures in use today include Stereotactic Thalamotomy (effective for tremor and rigidity), and Subthalamic Deep Brain Stimulation (which may also allow for a reduction in the medication being taken by the patient). The best candidates for surgery tend to be younger, healthier patients who have previously shown a good response to medical therapy.
There are other surgical approaches currently under study (including for example foetal cell transplantation), but none at this time have been sufficiently developed to be useful as therapies.
