Parkinson's disease: symptoms, causes, diagnosis and treatment

The NHS says the symptoms usually develop gradually and are mild at first, and that the order in which they develop and their severity is different for each person. It is unlikely that someone would experience all or most of them. Parkinson's UK counts over 40 symptoms, with three main ones.

The three main symptoms affect movement and are sometimes referred to by doctors as parkinsonism. The NHS describes them as below.

• Tremor: shaking that usually begins in the hand or arm and is more likely to occur when the limb is relaxed and resting.

• Slowness of movement (bradykinesia): physical movements are much slower than normal, which can make everyday tasks difficult and result in a distinctive slow, shuffling walk with very small steps.

• Muscle stiffness (rigidity): stiffness and tension in the muscles, which can make it difficult to move around and make facial expressions, and can result in painful muscle cramps (dystonia).

The NHS says Parkinson's disease also causes a range of other physical and mental symptoms, some of which can appear years before the movement problems. Loss of the sense of smell, for example, sometimes occurs several years before other symptoms develop.

Parkinson's disease is a progressive neurological condition. Parkinson's UK explains that people with Parkinson's do not have enough of the chemical dopamine in the brain because some of the nerve cells that make it have stopped working. Symptoms start to appear when the brain cannot make enough dopamine to control movement properly. The NHS says symptoms usually only start when around 50% of the nerve cell activity in the substantia nigra has been lost.

It is not infectious. Parkinson's UK says that unlike flu or measles, you cannot catch Parkinson's from someone. It also explains that parkinsonism is a term that covers several conditions with similar symptoms, of which Parkinson's is the most common.

The first signs are often subtle and easy to put down to something else. The NHS lists tremor, slow movement and stiff muscles as the main symptoms and notes that other symptoms, such as loss of the sense of smell, can come years before them. It also says that in the early stages a GP may find it hard to say whether you definitely have the condition because symptoms are usually mild.

If you are concerned that you or someone close to you may have symptoms of Parkinson's disease, the NHS says to see a GP, who will ask about the problems you are experiencing and may refer you to a specialist for further tests.

The NHS says no tests can conclusively show that you have Parkinson's disease. Your doctor bases a diagnosis on your symptoms, medical history and a detailed physical examination, and may ask you to perform simple mental or physical tasks such as moving or walking around.

If a GP suspects Parkinson's disease you will be referred to a specialist, usually a neurologist (a specialist in conditions affecting the brain and nervous system) or a geriatrician (a specialist in problems affecting elderly people). The NHS says the specialist will most likely ask you to perform a number of physical exercises to assess movement, and special brain scans, such as a single photon emission computed tomography (SPECT) scan, may be carried out in some cases to try to rule out other causes of your symptoms.

It is not known why the nerve cells are lost. The NHS says it is believed that a combination of genetic changes and environmental factors may be responsible. It says a number of genetic factors have been shown to increase risk, and that Parkinson's disease can run in families as a result of faulty genes being passed to a child, but that this is rare.

On environmental factors, the NHS says it has been suggested that pesticides and herbicides used in farming and traffic or industrial pollution may contribute, but the evidence is inconclusive. It also explains that some rarer types of parkinsonism have an identifiable cause, such as medication, other progressive brain conditions or a series of small strokes.

• Drug-induced parkinsonism, where symptoms develop after taking certain medicines, such as some antipsychotics, and usually improve once the medicine is stopped.

• Other progressive brain conditions, such as progressive supranuclear palsy, multiple system atrophy and corticobasal degeneration.

• Cerebrovascular disease, where a series of small strokes causes several parts of the brain to die.

The NHS says there is currently no cure, but treatments are available to help relieve the symptoms and maintain quality of life. They include supportive therapies such as physiotherapy, medicine, and surgery for some people. You may not need any treatment in the early stages because symptoms are usually mild, but you may need regular appointments so your specialist can monitor the condition.

A care plan should be agreed with your healthcare team and your family or carers, outlining the treatments and help you need now and are likely to need in the future, and it should be reviewed regularly.

Supportive therapies make living with Parkinson's disease easier. The NHS says a physiotherapist can work with you to relieve muscle stiffness and joint pain through movement and exercise, an occupational therapist can identify areas of difficulty in everyday life and ensure your home is set up for you, and a speech and language therapist can help with swallowing and speech problems.

On diet, the NHS says that for some people, dietary changes can help improve symptoms. It lists the changes below and says you may see a dietitian if your care team thinks you may benefit. It also advises eating a balanced diet containing all the food groups.

• Increasing fibre and making sure you drink enough fluid to reduce constipation.

• Increasing the amount of salt in your diet and eating small, frequent meals to avoid low blood pressure and dizziness when you stand up quickly.

• Making changes to your diet to avoid unintentional weight loss.

The NHS says regular exercise is particularly important in helping relieve muscle stiffness, improving your mood and relieving stress. If you are newly diagnosed or your symptoms are mild you could try vigorous activities such as team sports, cycling and running; if symptoms are complex or progressing, less strenuous activities such as walking or simple stretching and strengthening exercises.

Being diagnosed does not mean you have to stop working, according to the NHS, and many people keep working for years. You must inform the DVLA and your insurance company if you have been diagnosed, but you will not necessarily have to stop driving. The NHS also lists Parkinson's UK as the main support and research charity, with local groups and an online community forum.

The NHS says symptoms can get worse as the condition progresses, and it can become increasingly difficult to carry out everyday activities without help. Many people respond well to treatment and only experience mild to moderate disability, whereas a minority may not respond as well and can, in time, become more severely disabled.

The NHS says Parkinson's disease does not directly cause people to die, but the condition can place great strain on the body and make some people more vulnerable to serious and life-threatening infections. With advances in treatment, most people now have a normal or near-normal life expectancy. For complex Parkinson's disease, when treatment is unable to consistently control symptoms, medicines can still be adjusted under a specialist, and palliative care is discussed as the condition advances.

On the NHS, a GP refers you to a neurologist or geriatrician, and treatment, regular reviews and supportive therapies are organised through the specialist team and local services. The NHS says efforts are under way to increase the availability of supportive therapies such as physiotherapy for Parkinson's patients on the NHS, and your local authority can arrange a care and support needs assessment.

Some people see a neurologist privately for a faster diagnosis or second opinion, or pay for therapies. The NHS pages note that a diagnosis is clinical, so a private assessment relies on the same history and examination, and it helps to share the results with your GP so that medicines and reviews are coordinated.