What is the cause of Parkinson’s disease? Does a virus cause Parkinson’s disease?

Do I have Parkinson’s disease?

This article is meant only for people who have Parkinson’s disease or are taking care of someone with Parkinson’s disease.

It is essential to get evaluated by a specialist neurologist to be sure of the diagnosis of Parkinson’s disease. I do provide a simple tool for testing yourself for symptoms of Parkinson’s disease, which can be accessed from the main page. However, this is mostly a memory aid and should not be used for clinical purposes.

All clinical diagnoses and treatment should be done only under the direct advice of a certified doctor.

What causes Parkinson’s disease?

We will go step by step.

First, let us understand how normal movement works: The front of the head is the part that decides to make a movement – this is our free “will”. Then the mid-portion of the brain (above your ears) sends the signal to execute this movement.

But before this signal reaches our muscles, it has to pass through a complicated maze of circuits deep inside our brain that is called the “Basal Ganglia Circuitry” (see image). This circuitry modulates movement, making it smooth and precise.


The substantia nigra is an important part of this circuitry. It is located at the back of the head, just above the neck. It produces a chemical called “Dopamine” – remember the name of this chemical, it is very very important: “Dopamine”.

The Substantia Nigra produces an important chemical called DOPAMINE.

This dopamine travels forwards, deep into the brain, and helps the basal ganglia circuitry operate correctly.


In Parkinson’s disease, for some reason, the cells in the substantia nigra are gradually destroyed. Therefore, less dopamine goes to the basal ganglia. Therefore, the basal ganglia do not function properly, leading to problems with movement.

Although there are many such movement problems in Parkinson’s disease, the three most typical are:

    • Uncontrolled shaking or TREMOR
    • Slowness of movements or BRADYKINESIA
    • Stiffness of body parts or RIGIDITY

This combination of motor problems is called “Parkinsonism”.

What causes the death of dopamine-producing cells? What other processes can cause Parkinsonism?

In a minority of cases, the reasons for the death of dopamine-producing cells is known:

1. Toxins: In rare cases, the destruction of cells may be due to ingestion of toxic substances like MPTP & rarely pesticides. However, this is believed to be very, very rare. This kind of Parkinsonism probably occurs only in certain people such as industrial workers and iv drug abusers.

2. Genes: Some patients may have faulty genes that lead to the gradual death of these cells. Several such defective genes including PARK-1, PARK-2, LRRK2 etc. have been identified. However, genetically inherited or familial Parkinson’s disease is also relatively rare – only about 10% of cases have a family history of Parkinson’s disease.

Faulty genes can produce Parkinson’s disease.

3. As part of another disease: For example, the death of these cells can occur as part and parcel of a more generalized destruction of cells in the brain. This happens in diseases that cause dementia, such as Alzheimer’s disease, and other illnesses called “Diffuse Lewy Body disease” & “Frontotemporal Dementia”.

NOTE: A few other diseases can directly cause basal ganglia dysfunction – e.g. In Wilson’s disease, there is accumulation of copper throughout the entire body. When copper accumulates in the basal ganglia, it produces parkinsonism. Similarly, liver failure can cause parkinsonism due to accumulation of a metal called manganese in the basal ganglia.

Alzheimers Disease
Parkinsonism can occur as part of a more generalized destruction of cells in the brain, for example as part of Alzheimer’s disease.

4. Medications: Some medications can cause symptoms like Parkinson’s disease. These include medications used for vomiting (metoclopramide, levosulpuride, high doses of domperidone) and for psychiatric problems (haloperidol, risperidone etc).

These medications may cause symptoms similar to Parkinson’s disease by temporarily decreasing the production of Dopamine. But there is no death of cells and so this condition is not called Parkinson’s disease. Instead, it is called “Medication Induced Parkinsonism” (“Parkinsonism” means “Parkinsons-like disease”).

Medications 1
Medications given for constipation can worsen Parkinson’s disease.

Medication Induced Parkinsonism is further explained in another article.

Do the reasons above explain most of the cases?


In most cases, no apparent reason can be identified for the destruction of Dopamine-producing cells. This is called “Idiopathic Parkinson’s disease”. The word “idiopathic” means “without a known cause”.

human 1211467
In the vast majority of cases, the cause for destruction of cells in the Substantia Nigra is NOT known.

Are there any theories regarding the reason for Parkinson’s disease?

As noted before, the cause for destruction of the Dopamine-producing cells in most cases (almost 90%) is not known. What could be the cause of this destruction? If only we could find this cause, it would be a revolution in the treatment of Parkinson’s disease!

Of course, scientists are working furiously to find this answer.

There are a few theories:

Many scientists believe there is no single cause for Parkinson’s disease.

It is produced by different mechanisms in different people. For example: in the genetic form of Parkinson’s disease, the faulty genes may produce copious quantities of a toxic waste product. This waste product is called alpha-synuclein, and it can damage the substantia nigra. In some genetic forms, very reactive free oxygen radicals may directly damage the substantia nigra. In some patients, the body’s immune system may go haywire and start destroying the substantia nigra (a process called “autoimmunity”).

Faulty genes may produce too much waste called “alpha-synuclein”

An interesting theory that has come up recently is that at least some forms of Parkinson’s disease may be caused by a viral infection that starts in the gut.

Is Parkinson’s disease the result of a Viral infection?

Constipation is a very early symptom of Parkinson’s disease. This constipation may be due to a viral infection of the intestines. From the gut, the viruses gradually move towards the brain through a large nerve called the vagus nerve that connects the intestine to the brain. Such a process is known to happen in other diseases such as Polio.

The theory is, when the viruses eventually reach the brain, after many years, they cause havoc and destruction of the substantia nigra.

Gut e1572025002154
Parkinson’s may be caused by a viral infection that starts in the gut.

This is a fascinating theory that is rapidly gaining traction. Recently, scientists have successfully demonstrated that viruses and their even smaller cousins called prions are present in the vagus nerve and in the posterior part of the brain in Parkinson’s disease patients (Dourmashkin et al. 2018).

This research is exciting because it raises some very tantalizing questions: Can Parkinson’s disease be prevented by anti-viral medications? Can the progression of Parkinson’s disease be halted by killing these viruses?

The furious research effort into finding the cause of Parkinson’s disease is bound to produce results soon.

These are compelling questions which may revolutionize the way we treat Parkinson’s disease. Only time will tell us the answers.

Caution: This information is not a substitute for professional care. Do not change your medications/treatment without your doctor's permission.
Dr. Siddharth Kharkar

Dr. Siddharth Kharkar

Dr. Siddharth Kharkar has been recognized as one of the best neurologists in Mumbai by Outlook India magazine and India today Magazine. He is a board certified (American Board of Psychiatry & Neurology certified) Neurologist.

Dr. Siddharth Kharkar is a Epilepsy specialist in Mumbai & Parkinson's specialist in Mumbai, Maharashtra, India.

He has trained in the best institutions in India, US and UK including KEM hospital in Mumbai, Johns Hopkins University in Baltimore, University of California at San Francisco (UCSF), USA & Kings College in London.

Call 022-4897-1800

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NeuroPlus Epilepsy & Parkinson's Clinic - Dr. Kharkar IconNeuroPlus Epilepsy & Parkinson's Clinic - Dr. Kharkar

near LIC, Dr Balabhai Nanavati hospital, near LIC, Swami Vivekananda Road, LIC Colony, Vile Parle

4.6 87 reviews

  • Avatar Paras Prabhu ★★★★★ 6 months ago
    Out patient is epileptic from about 10 years and her seizure gotten worse during the past year with the frequency of about 3-4 times a week.So we consulted … More Dr. Kharkar. He tried a few medicines, and within 1.5-2 months now the patient is feeling very well now. There are no seizures for 14 days currently.Dr. tried to keep medicines as minimum as possible. He also tried to keep the cost of the treatment minimum.When some of the medicines started showing side-effects, he was quick to switch the medicines to the better options.Overall I think we are getting a best of the available treatments. We thank you very much Dr. Kharkar.
  • Avatar Dr Shobha Sankhe ★★★★★ a month ago
    Dr Kharkar is gem of a doctor with tremendous patience, empathy, genuine concern for his patients .He guides them very methodically & scientifically … More for their neurological ill healthOur epilepsy patient is extremely happy with his treatment , Patient feels better by just visiting him too!May his selfless service to humanity flourish to reach all the needy patients!!
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    I consulted Dr Sidharth for my sister who has become very hyper and aggressive and we could not understand the issue. Keeping in mind she is someone with … More special needs Dr Sidharth was extremely understanding of the situation and did not put her through unnecessary investigation and avoided a very long stay at the hospital. He was infact more keen on her returning home to her natural environment. We highly appreciate Dr Sidharth for his effort and for looking into the matter with utmost care. It was a very difficult decision for my family to get my sister admitted but we are glad we did it under his care.Thankyou Doc.
  • Avatar Prashant Purohit ★★★★★ a month ago
    my name is prashant purohit. I m become completely bed ridden from last 9 months and was unable to walk. I couldnt find out the cause even after visiting … More many doctors and many hospital in Ahmedabad nd jodhpur.started losing hope. A good friend of mine suggested to visit a neurologist. After searching a lot, I came to know about Dr. Siddharth Kharkar and took his appointment in Nanavati Hospital. He examined and said that he suffered from \u201cPKD(PAROXYSMAL KNESIGENIC DYSKNESIA\u201c. He assured us to reverse this in 5 days time. And indeed this happened. I started recovering miraculously. today I am fully well fit I m walking as normal . Many Many thanks to Dr. Siddharth Kharkhar sir for giving me a new life.
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  • Avatar N N ★★★★★ a year ago
    We visited Dr. Kharkhar for treatment regarding my mum - who is a multi-stroke patient and has aphasia. Certain medications were creating complications … More with her condition and Dr. Kharkhar was able to help mitigate the issue. We found him and his approach to be incredibly compassionate, considerate, individualized and patient-friendly. He advice is astute, up-to-date and empathetic. His treatment always comes from a deeply human place and is about seeing how to help the patient and their caregivers feel more at ease. Something that is quite rare and refreshing within the medical community.We feel that he genuinely cares about the patients that he is treating and is always kind and respectful in his communication. Moreover, his admin team is very efficient and prompt and it's a pleasure to deal with them.Would highly recommend Dr Kharkhar himself - though we must say our experience with Nanavati hospital itself has been less than ideal.Hope this helps.
  • Avatar Manish Ranjan ★★★★★ a year ago
    I have been visiting Dr Kharkar for treatment of my father. He is a very friendly doctor. He listens to our concerns with lot of patience. He also explains … More the issue in much greater details. He has really been of great help. My father is much better now.
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    One of the best Dr. Gives complete attention and time to listen to patient's history, issues. Explains various options of treatment with pros and … More cons.
  • Avatar Lawrence Castellino ★★★★★ a year ago
    Exceptional experience with an expert,Dr. Kharkar is a knowledge house. It is rare nowadays to find doctors with patience, knowledge, and a flair for … More handling patient’s questions, besides Dr. Kharkar’s bedside manners are exemplary. I am privileged to be treated by such an amazing soul. I have told him and will repeat it here that “I am advancing my move back to India although I am a US Citizen, because I know I am in good hands and will be well taken care of. Thanks Dr. Kharkar for your selfless service!
  • Avatar Hemant Kansara ★★★★★ a year ago
    Great doctor!! Really appreciate.The doctor diagnosed to my sister correctly and start treatment, she has good improvement after taking medicine prescribed … More by doctor as no epilepsy attake. We have good experience with the doctor. Thank you

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Noted as one of the best Neurologists in Mumbai

India Today Magazine - 2020, 2021, 2022, 2023

Outlook India Magazine - 2021, 2023

Ex-Assistant Professor, University of Alabama, USA

Outlook India - Best neurologist in Mumbai