Parkinson’s disease is mostly a clinical diagnosis. In other words, an examination by a doctor experienced in Parkinson’s disease is usually sufficient for diagnosis and treatment.

Although the formal criteria are somewhat complicated (bradykinesia, one of this, three of that etc…), it would be reasonable to simplify them for this article.

What are the main features of Parkinson’s disease?

There are three main symptoms of Parkinson’s disease. At least one of these symptoms is present, and slowness is almost always present.

  • Shaking = Tremor. This is the most easily recognized sign of Parkinson’s disease. Usually, the shaking only affects one hand or one leg in the early stages of the disease. The affected limb may shake both at rest, and while it is moving. Occasionally there might be shaking of the head.

    Shaking of hands is the most commonly recognized symptom of Parkinson’s disease.

  • Slowness = Bradykinesia. The patient’s movements become slow. Sometimes only the movements of a particular hand/leg become slow. But usually, there is some slowness of movement of the entire body. This is best noticed while walking. Relatives will often say “Well, she was one of the fastest walkers in the family. Now she walks slowly so that she gets left behind when we are walking in a group. After every 10 feet or so we have to wait so that she can catch up with us. Perhaps it’s old age…?”. This isn’t old age – It is frequently Parkinson’s disease and the good news is that it is curable.

    Walking slowly could be a symptom of Parkinson’s disease.

  • Stiffness = Rigidity. The patient’s body parts become stiff. This may be restricted to one hand so that, for the example, the patient has difficulty buttoning his shirt. A frequent complaint is that the patient is not able to reach the top of their head to comb or tie their hair. If a leg has become stiff, the patient may feel like he/she is dragging it while walking.

    Stiffness of the arms can make it difficult to comb hair, wear clothes or apply hair clips.

What are the other important features of Parkinson’s disease?

Now, in addition to these three main symptoms, the patient may also have other features which support the diagnosis of Parkinson’s disease.

There are many problems with movement in Parkinson’s disease.

  • Postural instability: Many doctors/guidelines consider this to be a core symptom of Parkinson’s disease. The patient is unstable while walking. Falls are not common in the early stages of Parkinson’s disease. But the patient may appear wobbly while taking turns, or if given a slight nudge in a crowded place.
  • An expressionless face.
  • Bending forwards while walking.
  • Shuffling while walking.
  • Freezing or getting stuck while walking.
  • Decrease in dexterity, or fine motor skills such as drawing.
  • Problems with thinking or memory (Dementia).

Which diseases can cause symptoms just like Parkinson’s disease?

These features are usually enough to make a clinical diagnosis of Parkinson’s disease. However, before the diagnosis can be made, two important things need to be ruled out:

  • Parkinsons-Plus syndromes can cause symptoms just like Parkinson’s disease.
  • Some medications can cause symptoms like Parkinson’s disease.

Parkinsons-Plus syndromes are diseases that appear to be just like Parkinson’s disease but are subtly different – e.g. in terms of eye movements, or early falls. These diseases have complicated names: Progressive Supranuclear Palsy (PSP), Multiple Systems Atrophy (MSA), Cortico-Basal Disease (CBD), etc…. These are further described here.

Certain medications can cause symptoms, just like Parkinson’s disease! This is an absolutely essential and often overlooked part of treating the patient. Some patients don’t require more medications, they require less!

Medications that can produce symptoms like Parkinson’s disease

Many medications used for psychiatric problems such as schizophreniaHaloperidol, Risperidal, Olanzapine, Aripiprzole, Trifluoperazine and many more. Clozapine and Quetiapine usually do not cause problems.
Some medications for mood and depressionFluphenazine, Tranycypormine, Lithium
Some anti-nausea medicationsMetoclopramide, Levosulpuride, High doses of domperidone about 30-40 mg/day, Flunarazine, rarely cinnarazine
Some heart and blood pressure medicationsAmiodarone, methly-dopa

If the patient has symptoms due to the side-effect of these medications, Amantadine is very useful. Sometimes trihexyphenidyl (Pacitane) is used for this purpose. Often there is a dramatic improvement in the patient’s functioning after removal of these medications and starting Amantadine.

Note: There are other things e.g. accumulation of minerals like copper, liver failure etc which can cause symptoms like Parkinson’s disease, but these are relatively uncommon and therefore we wont discuss them any further here. You can read more about these rare causes here. Usually, a basic set of blood tests (see below) can rule out most of these diseases.

Are additional tests needed?

Many doctors I know make a confirmatory diagnosis of Parkinson’s disease at this stage. If there are no red-flags, then a single office visit is usually enough to confirm the diagnosis.

Some doctors, including myself, do request some simple investigations (see box below). These are done to rule out rare causes. Usually, these tests do not show an additional problem.

Optional tests to rule out rare causes
– MRI Brain – CBC, LFT, RFT – TSH, PTH, Ceruloplasmin – Blood smear for acanthocytes In my clinical practice, these investigations change management only in about 10% of cases.

What is a DAT / TRODAT scan & F-DOPA scan?

Very rarely, the clinical diagnosis of a patient may be difficult. This can happen in two scenarios:

  • Very early Parkinson’s disease with very subtle symptoms.
  • When features of two different diseases are present – such as Parkinson’s disease and Essential tremor.

The diagnosis of Parkinson’s disease is usually very straightforward. Sometimes, it can be difficult.

In these cases, there are two options:

  • Treat with levodopa: if the patient responds he/she probably has Parkinson’s disease.
  • Do a DAT/TRODAT scan or even better – a F-DOPA PET scan.

The DAT/TRODAT & the F-DOPA scans can measure Dopamine activity inside the brain. Unlike an MRI which can only look at the structure of the brain, these scans are actually able to look at Dopamine activity itself. The image below is of a TRODAT scan:

The F-DOPA scan is superior overall to the DAT/TRODAT scan. It has higher resolution and more accurately measures the Dopamine activity. It also faster (overall about 1.5 hours) than a DAT/TRODAT scan which takes about 5 hours to be completed.

f-DOPA-PET scan: Note the relatively decreased brightness in the FIRST image.

However, the F-DOPA scan is slightly more expensive and is not available in all cities. In cities where the F-DOPA scan is not available, a DAT/TRODAT scan is a reasonable alternative.

Do all Parkinson’s disease patients need a DAT/TRODAT or F-DOPA scan?

No! Not at all!

First, the diagnosis of Parkinson’s disease is obvious in most patients. The proof of the pudding is in the eating. If you improve significantly with levodopa – you have parkinsonism. If this improvement is consistent for many years – you probably have Parkinson’s disease. (To know the difference between Parkinsonism & Parkinson’s disease, click here).

The proof of the pudding is in the eating. If you respond well to levodopa, then you have Parkinsonism.

Second, while these scans are useful in differentiating some diseases like Essential tremor from Parkinson’s disease, they are not very useful in differentiating many other diseases (e.g. the Parkinsons-plus syndromes).

Your doctor’s clinical examination beats these tests. These tests are a useful tool. Just like all tools in Parkinson’s disease, it is crucial to use them judiciously.


Dr. Siddharth Kharkar

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, Johns Hopkins University in Baltimore, University of California at San Francisco (UCSF), USA & Kings College in London.

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