Parkinson's disease
Introduction
Parkinson’s disease is a chronic (persistent), neurological condition that affects about 120,000 people in the UK. The condition was named after Dr James Parkinson, who first identified it in 1817. Parkinson's disease affects the way the brain coordinates body movements, including walking, talking and writing.
Parkinson's disease affects both sexes, although statistically, men are slightly more likely to develop the condition than women. The risk of getting the condition increases with age, with symptoms usually appearing in those who are over 50 years of age. However, younger people can also be diagnosed with Parkinson's disease.
When the symptoms of Parkinson's disease occur between 21-40 years of age, it is known as young-onset Parkinson's disease. If a person diagnosed with Parkinson's before the age of 18, it is known as juvenile Parkinson's disease, but this is extremely rare. Of the 10,000 people who are diagnosed with Parkinson's disease each year in the UK, 1 in 20 are under 40 years old.
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Symptoms
The symptoms of Parkinson's disease usually begin slowly and develop gradually, in no particular order. Parkinson's disease affects each individual differently and each person with the condition will have a different collection of symptoms and respond differently to treatment. The severity of symptoms also differs between individuals with the condition.
There are three main symptoms of Parkinson's disease which are outlined below.
Bradykinesia (slowness of movement)
If you have Parkinson's disease, initiating movement, such as starting to get out of a chair, can become difficult, and it can take you longer to perform tasks. You may also lack co-ordination in your movements. People often put this slowness of movement down to old age, and many do not have Parkinson's disease diagnosed until other symptoms occur.
Tremor (shaking)
Tremor (shaking) usually begins in one of your hands, or arms. It is more likely to occur when that part of your body is at rest, and usually decreases when you are using it. Shaking may become more noticeable when you are stressed, or anxious. However, the presence of tremor does not necessarily mean you have Parkinson’s disease, as it is a symptom of other conditions, including over-active thyroid (hyperthyroidism), multiple sclerosis, brain inflammation (encephalitis), and alcoholism. Although most people associate Parkinson's disease with tremor, up to 30% of people with the condition will not have this symptom.
Stifness of muscles (rigidity)
if you have Parkinson’s disease, your muscles may feel tense and, due to the stiffness, you may have trouble performing simple, everyday tasks. For example, you may find it difficult to turn around, get out of a chair, and roll over in bed. Making fine finger movements, facial expressions and body language may also become difficult.
Other symptoms associated with Parkinson's disease include:
- tiredness,
- constipation and bladder weakness,
- depression,
- problems with handwriting, speech, and balance, and
- difficulty swallowing.
Parkinsonism
The main symptoms of Parkinson's disease (shaking, stiffness and slowness of movement) are also the main symptoms of Parkinsonism, a collective group of conditions, of which Parkinson's disease is the most common.
Other less common forms of parkinsonism include:
- multiple system atrophy (MSA) - a neurodegenerative disorder that affects your motor system (the deterioration of brain signals to the muscles and limbs responsible for movement), and
- progressive supranuclear palsy (PSP) - another degenerative disorder that affects a person's vision and movement.
Both of the above disorders have similar symptoms and effects as Parkinson's disease.
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Causes
Parkinson's disease is caused by a loss of nerve cells in the part of your brain called the substantia nigra. The nerve cells are responsible for producing a chemical called dopamine which helps to transmit messages from your brain that control, and co-ordinate, your body movements.
If the nerve cells in your brain become damaged, or die, the amount of dopamine is reduced and the messages to your body become slow and abnormal. When 80% of the nerve cells have been lost, the symptoms of Parkinson's disease will appear. Over time, the level of dopamine will continue to fall slowly, and symptoms will become gradually worse.
The reason why nerve cell damage, associated with Parkinson's disease, occurs is currently unknown. However, two areas that are thought to be responsible are genetics (gene abnormalities) and environmental factors (toxins and pesticides). These areas are currently being researched in an effort to understand more about the role they play in relation to Parkinson's disease.
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Diagnosis
There are no tests that can definitely prove that you have Parkinson’s disease. Your GP will base the diagnosis on the symptoms you are experiencing, your medical history, and the results of a clinical examination.
In the early stages of Parkinson's disease, because your symptoms will usually be mild, your GP may find it difficult to say whether you definitely have the condition. You may be referred to a specialist if your GP suspects that you have Parkinson's disease.
The symptoms of Parkinson's disease are sometimes linked to environmental causes, such as toxins that kill dopamine-producing cells. In order to confirm, or rule out environmental factors, your specialist may carry out laboratory tests, such as blood tests, and scans, such as an MRI scan.
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Treatment
In the early stages of Parkinson's disease, you may not need any treatment because the symptoms will usually be mild. However, you may need to have regular appointments with your specialist so that the condition can be monitored.
At the moment, there is no cure for Parkinson's disease, but there are a range of treatments available to help control your symptoms, and maintain your quality of life. Medication is the main treatment option and there are three main types that are commonly used - levodopa, dopamine agonist, and monoamine oxidase-B inhibitors. These are described below in greater detail.
Levodopa
Levodopa is a medication that is absorbed by the nerve cells in your brain, and turned into dopamine. It is usually taken by mouth, in tablet or liquid form, and is often combined with other medication, such as benserazide, or carbidopa. This prevents the levodopa from being destroyed by enzymes (proteins) in your gut. These medicines also reduce the side effects of levodopa, which include nausea, vomiting, tiredness, and dizziness.
The first effects of levodopa often show a dramatic improvement in the symptoms of Parkinson's disease. However, levodopa tends to be less effective over time. This is because as more nerve cells in the brain gradually die, there are less to absorb the medicine. This means that the dose may need to be increased from time to time.
If the dose of levodopa is increased, there is an increased risk of developing side effects. For example, you may experience 'on-off' effects, where you can suddenly switch between being able to move (on) and being immobile (off). Muscle problems that cause uncontrollable, jerky movements (dyskinesias) is another problem associated with long term levodopa use.
Dopamine agonists
Dopamine agonists have a similar effect to levodopa, but they work in a different way. They lock on to the dopamine receptors in your brain, which receive signals from the dopamine that tell your body to move. Therefore, dopamine agonists act as a substitute for dopamine.
Unlike levodopa, dopamine agonists do not need to be converted in your body to become active. They are mostly prescribed in tablet form, but can also be taken by intravenous injection (injection in the vein). Dopamine agonists are sometimes taken at the same time as levodopa, in order to allow lower doses of levodopa to be used.
The possible side effects of dopamine agonists are similar to those of levodopa, and also include nausea and vomiting. However, episodes of confusion, or hallucinations, are more common with dopamine agonists, so they need to be used cautiously, particularly in the elderly, who may be more susceptible to these symptoms.
If you are prescribed a course of dopamine agonists, the initial dose will usually be very small, to prevent problems with nausea. The dosage is then gradually increased over a few weeks. If nausea is a problem, your GP may prescribe anti-sickness medication, such as domperidone.
Dopamine agonists used to be regarded as a 'top-up' treatment in addition to levodopa. However, in recent years, it has become a first-line treatment because people who take dopamine agonists are less likely to develop muscle problems (dyskinesias) than those on levodopa. Most people with Parkinson's disease will need to have levodopa eventually. However, dopamine agonists can delay the need for levodopa for months or, sometimes, years.
Monoamine oxidase-B inhibitors
Monoamine oxidase-B inhibitors are another alternative to levodopa as a treatment for early Parkinson's disease. They include selegiline and rasagiline which work by blocking the effects of a chemical called monoamine oxidase-B in the brain. This chemical destroys dopamine, so by blocking it, dopamine is able to last longer in the brain. Both of these medicines improve the symptoms of Parkinson's disease, although their effects are small compared to levadopa. They can be used alongside levodopa or dopamine agonists.
In some patients, selegiline can cause confusion. Rasagiline is more powerful than selegiline and has few side effects. Rasagiline has been proven to improve symptoms of Parkinson's disease at all stages of the illness.
As with dopamine agonists, people using these monoamine oxidase-B inhibitors will eventually need to use levodopa. However, by using the inhibitors first, the need for levodopa can be delayed.
Each of the medicines described above has to be prescribed to suit the individual needs of each person who has Parkinson's disease. Factors that can influence which medicine is prescribed include:
- your age,
- the severity of your symptoms,
- how well you respond to treatment, and
- whether or not you experience side effects.
Your specialist will advise you about the best medicine to take for your circumstances. Regular reviews will be needed as the disease progresses and your needs change.
Surgery
Surgery is sometimes used to treat people who have had Parkinson's disease for many years. However, surgery is not suitable for everyone.
Chronic deep brain stimulation is a surgical technique that is sometimes used to treat Parkinson's disease. This is where a pulse generator (like a heart pacemaker) is inserted in your chest wall. A fine wire is placed under the skin that attaches to your brain. A tiny electric current is produced from the pulse generator, which runs through the wire and stimulates the part of your brain which is affected by Parkinson's disease.
Although surgery does not cure Parkinson's disease, it does ease the symptoms for many people, particularly if medication is not working well.
Therapies
There are a number of therapies that can make living with Parkinson's disease easier. The three main therapies that are used are:
- physiotherapy,
- speech and language therapy,and
- occupational therapy.
Physiotherapy involves learning techniques which will help improve your movement, and make moving easier. A physiotherapist can help to relieve muscle stiffness and joint pain through movement and exercise.
About half of people with Parkinson's disease experience problems with communication, such as slurred speech, or poor body language. If you have problems with communication, a speech and language therapist can help you to improve your speech and use of language.
An occupational therapist can help identify problem areas in your everyday life, such as dressing yourself, or getting to your local shops. They can then help you to work out practical solutions.
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