What is Parkinson’s disease?

Parkinson’s disease is a disorder that affects the brain.[1] In healthy people, the thoughts, memory, emotions, touch, motor skills, vision, breathing, temperature, hunger and all the processes that regulate the body are controlled by the brain.[2]

In people with Parkinson’s disease (PD), the part of the brain that produces a chemical (dopamine) required for voluntary and smooth movement becomes damaged or dies.[3]

PD is a multifactorial disease and there could be several causes that could lead to disease development and damage to the brain cells (neurons).[4] These causes could mainly be due to the body’s faulty mechanisms like the build-up or clearing of unwanted proteins, weakened function of the powerhouses of the cells (mitochondria), or chemicals released by the brain’s immune cells (microglial cells).[4] Other causes may be genetic or coming into contact with harmful substances in the environment.

What are the symptoms of Parkinson’s disease?

Not everyone with these symptoms will have PD, and not everyone with PD will experience all of these symptoms. They may be caused by other, more common conditions. But if you have any of the below-mentioned symptoms, it is important to get them checked by your doctor.

The most common symptoms of PD include:[1,3,5,6,7]

  • Slowness of movement (bradykinesia)
  • Muscle stiffness
  • Shaking (tremor), especially while resting.

The other wide range of physical and psychological symptoms that a person with PD can experience are as follows:[1,3,5,7] 

Involuntary functions like:

  • Difficulty in bowel movements (constipation)
  • A drop in blood pressure when changing position from sitting to standing, experienced as a feeling of fainting (lightheadedness), sensation of spinning or losing one’s balance (dizziness) or actual fainting
  • Too much sweating even when it is not hot or even when the person is not anxious
  • Problems with urination such as involuntary loss of urine (incontinence) or difficulty emptying the bladder
  • Sexual health problems like decrease in desire to have sexual relations (loss of libido).


Changes in mood and thinking like:

  • Depression and anxiety
  • Lack of motivation and interest in activities (apathy)
  • Memory or thinking (cognitive) problems
  • Seeing things that are not there (visual hallucinations) and having false beliefs (delusions).


Other physical changes like:

  • Too much saliva in the mouth due to decreased swallowing ability (drooling)
  • Too much sleepiness or tiredness (fatigue) during the day
  • Problems with balance which can increase the chances of falling down
  • Loss of smell experienced as decreased ability to identify specific smells
  • Problems falling asleep (insomnia), acting out in dreams (rapid eye movement (REM) sleep behaviour disorder), or uncontrollable urge to move the legs (restless leg syndrome)
  • Pain in one part of the body or the entire body
  • Changes in skin such as from oily to dry
  • Speech problems experienced as slowness or unclear speech which is difficult for the others to hear (mumbling) or unclear speech where sounds of words get mixed (slurring)
  • Swallowing problems (dysphagia) seen as choking, coughing or clearing throat while eating or drinking
  • Visual changes like dry eyes, double vision and difficulty reading
  • Weight loss which can be mild to moderate
  • Reduced facial expression (mask-like face)
  • Changes in a person's writing style (Micrographia)
What are the different types of Parkinson’s disease?
  • Parkinson’s disease / Idiopathic Parkinson’s.[8] 80%–85% of people with Parkinson’s disease.[8]
  • Familial Parkinson’s.[8] 15% of people with Parkinson’s disease.[8]
  • Early-onset or young-onset Parkinson’s.[8] 10%–15% of people with Parkinson’s disease.[8]
What causes Parkinson’s disease? Who is at risk of Parkinson’s disease?

The reason why some people get PD is not completely understood. However, there are some factors that are known to increase the chance of a person developing this disease called ‘risk factors’. Having a risk factor does not mean that you will definitely get the disease, but the more risk factors you have can make it more likely. Some risk factors for PD are:[1,3]


  • Genetics: Chances of a person having Parkinson's disease increase (but are not guaranteed) when this disease runs in the family.

This happens when the disease is inherited due to the passage of faulty genes from parents to the child.


  • Environmental factors: Some researchers have suggested that environmental factors like pesticides and herbicides used for farming and for traffic, or industrial pollutants might contribute to this condition.


Men are twice as likely to have PD than women.[1,3] Most people with PD start to develop symptoms when they are in their 60s, however, some people might first experience symptoms when they are under 40 or 50 years.[1,3]


The mechanisms that cause PD are explained in detail below:[4]


  • The build-up of a misfolded protein called alpha-synuclein within neurons is toxic for the neuron and plays a key role in developing PD. In normal situations, unwanted proteins are cleared by the body’s chemical processes, however, due to this abnormal protein structure, they are unable to do so, inevitably resulting in the death of the neurons.
  • Fault in the mitochondrial activity occurs. In normal situations, old or damaged mitochondria are cleared by the body, however, this recycling is disturbed in PD leading to mitochondria build-up.
  • Immune response due to chemicals released by the immune cells of the nervous system.


Since these mechanisms mainly happen in the parts of the brain that are responsible for physical movement, this is why people with PD experience symptoms affecting physical movement.[1,3,6,7]

Greater understanding of what causes PD will help researchers find more effective ways to treat and manage it.

Learn more about Parkinson’s disease

How is Parkinson’s disease diagnosed?

If your doctor thinks you might have PD, they will ask questions about symptoms, examine a certain part of the brain, refer you to a specialist (like a neurologist and/or a geriatrician), run certain mental or physical tests.[9,11]


  • Brain scans like CT, MRI, PET and DaTscan.[10,11,12,13,14]
    • A CT (computed tomography) scan is a type of imaging technique where X-rays are passed through the body from different angles to make pictures of the brain.[11,12] It helps to rule out other causes like vascular disease or tumours for Parkinson’s-like symptoms.[11]
    • An MRI (magnetic resonance imaging) scan is a type of imaging technique where a strong magnetic field and radio waves are used to produce detailed images of the inside of the brain.[11,13] It helps to distinguish Parkinson’s disease from other Parkinson’s-like conditions.[11]
    • A PET (positron emission tomography) scan is a type of imaging technique that detects the radiation given off by a substance injected beforehand.[14] PET is an imaging test that helps to show how aspects of your brain are working. It does so by helping to reveal the biochemical or metabolic function of your brain.
    • A DaTscan (Dopamine Transporter Scan) is a type of imaging technique where a small amount of radioactive material is injected into the blood, where it circulates around the body and makes its way to the brain, where it is captured with a camera as an image.[11] This image is used to identify the loss of dopamine-producing brain cells leading to Parkinson’s. It helps to distinguish Parkinson’s disease from other conditions with similar symptoms.[10,11]

  • New imaging techniques are being developed and research is ongoing to detect Parkinson’s with new blood test, skin test and reliable smell test, heart scans (MIBG) [11,20]

What are the stages of Parkinson’s disease?

Symptoms of PD usually begin with early symptoms and the disease is known as ‘early/initial’ at this stage. PD may get worse over time. This is also known as ‘progressive disease’, or ‘disease progression’. As PD progresses, the symptoms become more severe from mid-stage to advanced-stage.

In 1967, Hoehn and Yahr defined five stages of PD based on clinical instability. This helped to classify PD into the early-stage represented by stages 1 and 2, the mid-stage represented by stages 2 and 3 and the advanced stage, represented by stages 4 and 5.[15]

PD can be divided into three main stages:[15]


  • Early-stage: Early-stage PD is the first stage of the disease, where the person shows mild symptoms which do not interfere with daily activities. The person is able to live independently, but daily tasks require time and become difficult.
  • Mid-stage: In mid-stage PD, the person is functionally restricted in their daily activities but is physically capable of living an independent life. The disability is mild to moderate at this stage.
  • Advanced-stage: Advanced-stage PD is the final stage of the disease, where symptoms are fully developed and debilitating, making the person bedridden or bound to a wheelchair. Around-the-clock care is required for all activities.


Some doctors use a more complex scale to make sure that not only physical symptoms but all aspects of the disease are included in staging.[16]

What does it mean to be a carrier for Parkinson’s disease?

In rare cases, PD is caused by a change (known as 'mutation') in the genes that are passed on from parents. Some of the most common gene mutations a child can inherit from their parents are GBA, PRKN and PINK1.[17]

People who are carriers of PD will not develop PD but may show milder or early symptoms of a condition called parkinsonism which describes several Parkinson’s-like symptoms like tremors, muscle rigidity and slowness of movement.[17]

What treatment options are available for Parkinson’s disease?

At the moment there is no cure for PD, so treatments are used to relieve symptoms in order to improve quality of life. The main treatments used for PD are:[1,3,18,19]


  • Supportive therapies:
    • Physiotherapy can support people with PD to relieve muscle stiffness and joint pain through exercise and movements. This helps overall to improve the person’s fitness and ability to manage things independently.
    • Occupational therapy can identify the difficulties faced due to PD in everyday life and can work out practical solutions to ensure a safe and appropriate home setup and to maintain independence as long as possible. There is also growing use of smart home technology.
    • Speech and language therapists help the person with PD to solve problems by teaching how to speak and perform some swallowing exercises, or by some assistive therapy.
    • Dieticians can help with making dietary changes, which can improve some symptoms such as increasing fibrous food in the diet and drinking enough fluids to reduce constipation, increasing salt intake in the diet and eating small and frequent meals to avoid issues with low blood pressure, and making changes to the diet to avoid unintentional weight loss.
  • Medications: Medications that are metabolised to or imitate the chemical dopamine, substances that initiate a physiological response when combined with a receptor (dopamine agonists), and medicines that block the breakdown of dopamine (monoamine oxidase-B inhibitors). Oral and injectable options are available.
  • Surgery: Deep brain stimulation is a procedure, which involves surgically implanting a pulse generator in the brain (similar to a heart pacemaker in the chest wall). This is connected to one or two thin wires under the skin and is correctly inserted in specific areas in the brain. A tiny electric current produced by this generator stimulates the part of the brain that is affected by PD, which might ease some symptoms for some people.
  • Focused ultrasound: It is an alternative to deep brain stimulation and offers a non-invasive surgical procedure for Parkinson’s motor symptoms or other movement disorders that are characterised by uncontrolled, involuntary movements (dyskinesia).
  • Additional symptoms may need to be treated separately.

What is the outlook for a person with Parkinson’s disease?

Clinical trials (which can also be called ‘research studies’) are designed to look at how safe experimental drugs or procedures (such as new types of surgery) are and how well they work. Researchers are working hard to learn more about PD by researching on how to slow or halt the breakdown/death of brain cells (neurodegeneration) by enhancing the clearance of abnormal proteins and blocking their communication, improving mitochondrial activity and targeting the inflammation of neurons.[19]

Furthermore, topics of research include immunotherapies, using established drugs for a new indication (drug repurposing), targeting a specific type of chemical messenger (neurotransmitter) system called non-dopaminergic neurotransmitter systems, components relating to the growth of nervous tissue called neurotrophic factors, regenerative treatments and advances in deep brain stimulation.[18,19]

As researchers learn more about PD, clinical trials will be set up to look at potential new treatments.

If you would like to know more about Roche sponsored clinical trials or are interested in taking part in a clinical trial, speak to your doctor or visit the Roche ForPatients clinical trials page.

References and further resources

1. NHS. Parkinson’s disease. Overview. Accessed 16 January 2023. Available from: Link

2. John Hopkins Medicine. Brain anatomy and how the brain works. Accessed 16 January 2023. Available from: Link

3. National Institute of Neurological Disorders and Stroke. Parkinson’s Disease. What research is being done? Accessed 16 January 2023. Available from: Link

4. Poewe W, Seppi K, Tanner C.M, et al. Parkinson disease. Nat Rev Dis Primers. 2017 Mar 23; Volume(3):Article(17013). Available from: Link

5. NHS. Parkinson’s disease. Symptoms. Accessed 16 January 2023. Available from: Link

6. Michael J. Fox Foundation for Parkinson’s research. About Parkinson’s. Symptoms. Accessed 16 January 2023. Available from: Link

7. John Hopkins Medicine. How Parkinson’s disease is diagnosed. Accessed 17 January 2023. Available from: Link

8. Parkinson’s News Today. Types of Parkinson’s Disease. Accessed 17 January 2023. Available from: Link

9. NHS. Parkinson’s disease. Diagnosis. Accessed 16 January 2023. Available from: Link

10. American Parkinson Disease Association. What is a DaTscan and should I get one? Accessed 18 January 2023. Available from: Link

11. Parkinson's Europe. How is Parkinson’s diagnosed? Diagnosis. Accessed 17 January 2023. Available from: Link

12. NHS. CT scan. Accessed 18 January 2023. Available from: Link

13. NHS. MRI scan. Accessed 18 January 2023. Available from: Link

14. NHS. PET scan. Accessed 18 January 2023. Available from: Link

15. Parkinson's Foundation. Stages of Parkinson’s. Accessed 17 January 2023. Available from: Link

16. International Parkinson and Movement Disorder Society. MDS-UPDRS. The MDS-sponsored Revision of the Unified Parkinson’s Disease Rating Scale. Accessed 23 January 2023. Available from: Link

17. Parkinson's Foundation. Understanding genetics. Accessed 17 January 2023. Available from: Link

18. NHS. Parkinson’s disease. Treatment. Accessed 16 January 2023. Available from: Link

19. Thomas B. Stoker and Roger A. Barker. Recent developments in the treatment of Parkinson’s Disease. F1000Res. 2020 July 31;9:F1000 Faculty Rev-862. Available from: Link

20. Skowronek C, Zange L and Lipp A. Cardiac 123I-MIBG Scintigraphy in Neurodegenerative Parkinson Syndromes: Performance and Pitfalls in Clinical Practice. Front Neurol. 2019 Feb 26; Volume(10):152. Available from: Link

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