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 very important to get evaluated by a specialist neurologist to be certain 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 by clicking here. 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 advise 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 complex 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 substaita 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”.
This dopamine travels forwards, deep into the brain, and helps the basal ganglia circuitry operate properly.
In Parkinson’s disease, for some reason, the cells in the substantia nigra are gradually destroyed, so that less dopamine goes to the basal ganglia. As a result, the basal ganglia circuitry does not function properly leading to many different problems with movement. These have been described in detail in another article. But in short, the 3 most important movement problems are:
- Uncontrolled shaking or TREMOR
- Slowness of movements or BRADYKINESIA
- Stiffness of body parts or RIGIDITY
What causes the death of dopamine-producing cells?
The reason for the death of dopamine-producing cells in the substantia nigra is not known.
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 and occurs only in certain people such as industrial workers and iv drug abusers.
Sometimes, 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 diseases called “Diffuse Lewy Body disease” & “Frontotemporal Dementia”.
Some patients may have faulty genes that lead to gradual death of these cells. A number of such faulty 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.
However in most cases no clear reason can be identified for the destruction of Dopamine-producing cells. This is “TRUE” or idiopathic Parkinson’s disease. The word “idiopathic” means “without a known cause”. Parkinson’s disease is more common in elderly people, but most people do not believe that it is age itself that causes destruction of these cells. Most people believe there is a different reason, that we still don’t know about.
Note: 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) may cause Parkinson’s disease like symptoms 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 (or Parkinsons-like disease). The difference is further explained here.
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 toxic waste products called alpha-synuclein that can damage the substantia nigra. In some genetic forms, very reactive free oxygen radicals may directly damage the substatia nigra. In some patients, the body’s immune system may go haywire and start destroying the substantia nigra (a process called “autoimmunity”).
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.
Constipation is a very early symptom of Parkinson’s disease. It is believed that, at least in some people, this constipation is caused by a viral infection of the gut. From the gut, the viruses gradually move towards the brain through a large nerve called the vagus nerve that connects the gut to the brain. Such a process is known to happen in other diseases such as Polio. When the viruses eventually reach the brain, after many years, they cause havoc and destruction of the substantia nigra.
This is very exciting research that is rapidly gaining traction. As of 2019, 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? These are very exciting questions. Only time will tell us the answers.
Dr. Kharkar is a Neurologist, Epilepsy specialist & Parkinson’s disease specialist in Mumbai, Maharashtra, India.
He has trained in the best institutions in India, US and UK including KEM hospital in Mumbai, University of California at San Francisco (UCSF), USA & Kings College in London.
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