What is Parkinson's disease?
Parkinson's disease is a progressive disease of the nervous system which affects around one person in every 500 in the UK. The disease becomes more common with increasing age. Symptoms usually first appear in people over the age of 50, although younger people can also develop the disease.
There is no evidence that Parkinson's disease is hereditary, although in around 5 per cent of cases there is another family member affected. It is believed that genetics may make some people more prone to developing Parkinson's disease but only if combined with exposure to external factors. To date, scientists have identified nine genes linked to Parkinson's disease.
What are the symptoms of Parkinson's?
The main symptoms of Parkinson's disease are tremor, stiff muscles and joints, and slowness or difficulty in walking.
In most people the presenting symptom of the disease is tremor, which usually begins on one side of the body (unilaterally) in the hand or arm. The tremor usually occurs at rest and decreases when the affected part is being used. It usually increases during times of stress or heightened emotion and decreases during sleep.
Stiffness or rigidity of the muscles can also occur - this can be quite painful and can cause difficulty in performing many everyday movements. Walking may be slowed and it can be difficult to start to walk. A lack of co-ordination may also cause problems.
Other symptoms include difficulties with balance, speech and writing and sometimes a lack of facial expression, altered posture and tiredness.
Some people may also experience symptoms unrelated to movement, such as memory impairment, mood disorders, sleep difficulties, loss of smell, constipation and drooling.
What causes Parkinson's?
The reasons why people develop Parkinson's disease are not yet fully known. However, it is known that it is caused by a decrease in the nerve cells in a particular area of the brain called the substantia nigra. These cells produce and store dopamine, a chemical messenger involved in the co-ordination of movements in the body. The amount of dopamine being produced is therefore reduced while the level of acetylcholine, another chemical messenger, remains normal causing an imbalance between the two. Symptoms of Parkinson's disease usually appear when around 80 per cent of the dopamine-producing cells have been lost.
What treatment is available?
Currently, there is no cure for Parkinson's. However, there are drugs available which are used to restore the balance between dopamine and acetylcholine and which can help to control some of the symptoms.
Levodopa is a natural amino acid that has been used to treat Parkinson's disease since the 1960s. Levodopa is converted into dopamine by an enzyme in the brain. In order to prevent the levodopa being metabolised by this enzyme before it reaches the brain it is given in combination with an enzyme inhibitor (eg, benserazide, carbidopa) that blocks the enzyme in the gastrointestinal tract. The inhibitors are not able to pass into the brain and therefore, do not inhibit the conversion of levodopa into dopamine in the brain. Levodopa considerably improves symptoms such as stiffness and slowness of movement.
The most commonly prescribed preparations are Madopar® (levodopa and benserazide, or 'co-beneldopa') and Sinemet® (levodopa and carbidopa, or 'co-careldopa'). There are different strengths of these preparations and controlled release forms are also available. Duodopa® is a gel containing levodopa and carbidopa that is administered directly into the small intestine via a permanent intestinal tube known as a port. The gel is administered continously by a small portable pump. Because administration is continuous, this form of administration may be useful in people who have severe fluctuations in their symptoms throughout the day and uncontrollable or impaired voluntary movements. It is only licensed for use in people whose symptoms cannot be controlled by other Parkinson's treatments.
Of those people who respond to treatment with levodopa, around two thirds will experience some loss of benefit after two to five years as their body becomes tolerant to the drug. Some people will then experience a progressive recurrence of their parkinsonian disability.
Other people, especially younger patients, will develop fluctuations in their mobility throughout the day - this is known as end-of-dose deterioration or the 'wearing-off' effect. Sometimes this effect can be managed by decreasing the time between doses of levodopa. In some people this may not be effective and the change between mobility and immobility may become more abrupt - this is known as the 'on/off' effect.
Dopamine agonists stimulate the parts of the brain where dopamine acts. They can be taken alone or sometimes in combination with Sinemet® or Madopar®. They produce fewer long-term side effects such as the on/off effect and are therefore often used in younger patients. Commonly prescribed examples are bromocriptine (eg, Parlodel®) and ropinirole (eg, Ipinnia XL®, Requip®, Raponer XL®).
Apomorphine (APO-go®) is an injectable dopamine agonist, which acts very quickly and can be used for people who experience extreme variations in mobility and need to be active at specific times. Cabergoline (eg, Cabaser®) and pergolide may be used in combination with levodopa, and pramipexole (eg, Mirapexin®) may be used alone or in combination with levodopa.
Rotigotine (Neupro®) is a new dopamine agonist that is available as a skin patch applied once daily. The patch may be useful for people who have difficulty swallowing. It may be used alone in the early stages of Parkinson's disease or in combination with levodopa.
Amantadine promotes the release of dopamine and can help to reduce involuntary movements, but as it has only a mild effect it is suitable for a smaller number of people.
Anticholinergics are used to redress the balance between acetylcholine and dopamine by blocking the action of acetylcholine. They are often used in younger people with milder symptoms. These include orphenadrine, procyclidine (eg, Kemadrin®) and trihexyphenidyl.
COMT inhibitors are a newer class of drugs that block COMT, an enzyme which breaks down levodopa. This class includes entacapone (eg, Comtess®), opicapone (Ongentys®) and tolcapone (Tasmar®). A combined product containing entacapone plus levodopa and carbidopa is also available (Sastravi®, Stalevo®).
Selegiline (eg, Eldepryl®, Zelapar®) and rasagiline (eg, Azilect®) slow down the breakdown of dopamine and can increase the effectiveness of Sinemet® or Madopar®. Safinamide (Xadago®) is another drug that works in a similar way.
The use of surgery to treat Parkinson's disease has been largely abandoned since the introduction of levodopa and other drugs. However, recently there has been renewed interest and new surgical techniques are currently being researched.
How does it affect a person's life?
Most people with Parkinson's disease can lead a long and busy life. Life expectancy is the same as for people who do not have the disease.
Problems with everyday life such as with writing, driving a car, mobility and communication difficulties can all be experienced. However, much help and support are available. Physiotherapy, speech and language therapy and occupational therapy are all beneficial.
- Keeping active can help to loosen stiff muscles and improve speech or posture.
- If you shuffle when walking, wear leather soled shoes to help you keep your balance.
- Try to keep your weight at a normal level as being overweight puts additional strain on your joints and may affect your mobility.
- Try to relieve symptoms of anxiety as this can make any tremor more severe and can also affect your sleep.
Further information available from:
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Fact sheet provided by MIMS
Date last reviewed: November 2014