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What Is Parkinson's Disease?

Parkinson’s disease is an illness that affects the brain. It is caused by a problem in the part of the brain that produces a chemical called ‘dopamine’. This normally helps with coordination and the smooth movement of muscles.

Therefore, when there is a problem in this part of the brain and the amount of dopamine is reduced, the body isn’t able to control its movements normally. The symptoms of the disease get worse with age.

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Who gets Parkinson’s disease?

The exact cause of Parkinson’s disease is still unknown, but it is likely to be due to a combination of genetic and environmental factors. It tends to affect people over the age of 50 years, although in rare cases it can affect younger people. The risk increases as people get older, and it is slightly more common in men than women.

What symptoms does it cause?

Parkinson’s disease causes three main symptoms: involuntary shaking (tremor), stiffness (rigidity) and slowness of movement (bradykinesia). For many people, these symptoms will develop over a long period of time.

There are also other symptoms that are associated with coordination and control of muscles. These include difficulty with fine movements (like tying shoelaces or handwriting), slower walking (with shorter, shuffling steps), problems with balance, showing fewer facial expressions, and difficulties with speech and swallowing.

More rarely, or in people where the disease has become advanced, the following symptoms may occur: problems with bladder and bowels (such as incontinence), a change in sense of smell, problems with sleep, sexual dysfunction, and hallucinations (hearing or seeing things that aren’t there).

Since the part of the brain affected by Parkinson’s disease does not normally control memory, dementia does not often occur in the early stages. However, people with Parkinson’s disease are at a higher risk of developing dementia as the condition progresses.

How is it diagnosed?

There is no single test to diagnose Parkinson’s disease, so diagnosis is based on the symptoms described above. The diagnosis will be made by a doctor who specialises in movement disorders.

They will have experience distinguishing Parkinson’s disease from other conditions that may also have similar symptoms, such as a drug-induced Parkinsonism (the side effects of certain medicines result in a Parkinson’s-like condition).

The doctor may also do some other tests to provide more information about the condition. These may include a scan of the brain, blood tests, and a test of the patient’s sense of smell.

What treatments are available?

There is currently no cure for Parkinson’s disease. Treatments therefore aim to manage symptoms such as shaking or movement problems. If the symptoms are not affecting a patient’s day-to-day activities, doctors may not immediately start treatment. Instead they will monitor the disease to see how it is affecting the patient.

If the symptoms of Parkinson’s disease start to cause problems, then medication will usually be started.

There are different types of medications used to treat Parkinson’s disease. These include dopamine ‘agonists’ (chemicals that act in the same way as dopamine), and monoamine oxidase inhibitors.

Dopamine agonists

These medicines act on the same receptors in the brain as dopamine and mimic its effects (fooling brain cells into thinking they are dopamine).

Known side effects of dopamine agonists

In general, the side effects of dopamine agonists include:

  • Nausea
  • Drowsiness
  • Impulsive behaviour. This is when someone may find it difficult to control the urge to do things they wouldn’t normally do or take risks they usually might not. Although this is rare, it is more common with this group of medicines than other medicines for Parkinson’s disease.


Levodopa is an example of a dopamine agonist. It is broken down in the brain to dopamine. Levodopa is always given with another medicine, like carbidopa, to make sure it is converted into dopamine in the correct part of the brain.

Known side effects of levodopa

The common side effects of levodopa include:

  • Nausea
  • Dizziness
  • Headache
  • Loss of appetite.

Levodopa tends to work less well as time progresses; this may mean increasing the amount or frequency, of levodopa taken.

Over time, muscle problems like involuntary jerking movements (dyskinesia) may also develop. Some people also develop an on-off pattern with the medicine; sometimes the medicine will be ‘on’ and symptoms will be well controlled, and other times it will switch to ‘off’ and cause quite severe stiffness.

A Duodopa (levodopa and carbidopa gel) infusion may be offered to patients if the ‘on-off’ effects are quite severe or symptoms are no longer responding to oral medication. During a Duodopa infusion, a small tube is inserted through the skin directly into the gut (small intestine), and a pump is used to provide a continuous supply of medication into the body. This can reduce the ‘on-off’ issues seen with the oral medication. For more information about this type of treatment, see our page on ‘Advanced medical therapies: pumps and infusions’.

Monoamine oxidase inhibitors are another group of medications used to treat Parkinson’s disease. They work by stopping the body breaking down dopamine, and so allow the effect of dopamine to last longer. However, the use of monoamine oxidase inhibitors is limited since they can interact with other medicines that a patient might also be taking, such as antidepressants.

Known side effects of monoamine oxidase inhibitors

The common side effects of monoamine oxidase inhibitors include:

  • Dizziness
  • Headache
  • Confusion and agitation
  • Nausea.


Other medicines

There are other medicines that may be useful for treating specific symptoms of Parkinson’s disease. The doctor will discuss the best treatment options for each patient and monitor their medication to achieve the best control of symptoms.


Additional support services

Keeping as active as possible and paying attention to diet can help ease muscle stiffness and manage the condition. As well as our movement disorder specialists, other health specialists such as physiotherapists, dieticians, and occupational therapists can also provide support. The London Clinic provides a wide range of these additional services.

What is the outlook for patients with Parkinson’s disease?

Symptoms of Parkinson’s disease tend to progress over time. There isn’t yet a cure for the disease, or a medicine that will stop it getting worse in people who have it.

For some people with Parkinson’s disease, they will have a period where their symptoms are mild and don’t affect their day-to-day lives. However, each person is different and it is very difficult to predict how the disease will progress.

Research is ongoing, and there are some studies that are looking at ways to stop the affected brain cells deteriorating or dying, rather than just controlling symptoms.

Why choose The London Clinic?

At The London Clinic, we are committed to delivering quality, patient-centred care at the cutting edge of innovation. We offer access to the very best facilities and equipment, and to leading specialists in the field of movement disorders who work alongside clinical support teams that are second to none.

What The Experts Say

Deep brain stimulation is a life transforming therapy. Two thin electrodes precisely inserted into the brain are connected to a chest pacemaker to jam abnormal brain signals causing unwanted movements.

At The London Clinic we have the UK’s first and only private hospital deep brain stimulation team of experienced surgeons and neurologists, using all the latest devices. Surgery is done asleep for comfort using tiny holes in the head with a minimally invasive, low profile technique and minimal hair removal.


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