How Parkinson's Disease Is Diagnosed

There's no "gold standard" test that will diagnose Parkinson's disease (PD). Instead, a physician relies on their own clinical observations and judgment, along with a patient's description of possible signs and symptoms, to make the diagnosis. That, of course, makes a physical examination very important in this process. Much of your doctor's exam will be aimed at assessing whether you have the so-called cardinal signs of Parkinson's: resting tremor, rigidity (stiffness), bradykinesia (slowness of movement) and postural instability (impaired balance).

Self-Checks/At-Home Testing

Make note of any symptoms you have been experiencing that are of concern. These include classic Parkinson's symptoms, but can also include a variety of others, as the disease affects nerves throughout your body.

These may appear even earlier than the movement problems and can include:

  • Reduced facial expressions
  • Trouble tying your shoes or buttoning your shirt
  • Slurred or softer speech
  • Reduced sense of smell
  • Constipation or slow digestion
  • Drop in blood pressure when you stand up
  • Sleep disturbances
  • Restless leg syndrome
  • Impulsive behaviors
  • Mood changes
  • Changes in your thinking and memory abilities

Recognizing any of these is in no way confirmation that you have Parkinson's disease. But a log of this information (what you're experiencing, how long it has been going on, the circumstances under which it happens, etc.) can be very useful to your doctor as they work to make a diagnosis.

Physical Examination and Tests

A trip to the neurologist’s office often includes what seems like dozens of questions, along with multiple tests.

There currently are no diagnostic blood tests for Parkinson's disease, but your doctor may do some routine blood and urine tests to assess your overall health. Your blood pressure will be taken sitting and standing to look for orthostatic hypotension.

A movement disorder specialist will do a variety of physical tests to assess you as well.

Looking for Tremors

Resting tremor often is the first symptom of Parkinson's disease. Your doctor likely will watch for it in your hands when you're seated with your arms relaxed and your hands in your lap. Sometimes, particularly early in the disease, patients need to be distracted (for example, by counting backward from 10) in order to bring out this tremor.

In addition to resting tremor, your doctor will watch for postural tremor, which occurs when your arms are in an outstretched position. They may also look for kinetic tremor, which occurs with voluntary movement and is usually assessed by the finger-to-nose test (where you are asked to touch your nose with your index finger and then touch the examiner’s finger, which changes positions with each try).

Although resting tremor is expected in Parkinson's disease, many people with the condition have a combination of different types of tremors.

Gauging Speed of Movement

Bradykinesia occurs in most people who have Parkinson's. It may cause a lack of spontaneous facial expression and fewer eye blinks per minute than usual, and your doctor will look for these signs in your physical exam.

Your doctor also may assess your speed of movement by asking you to open and close each hand or tap your index finger against your thumb repeatedly, making large movements as quickly as possible. In people with Parkinson's disease, the movement may start off fast and precise, but it will deteriorate quickly, becoming slow and limited.

Gait is also another way to test for this. Observing a patient while they walk, noting the length of their stride as well as the speed at which they move, can tell doctors quite a bit. Lack of arm swing is also a feature that appears fairly early in those with Parkinson's.

Assessing Level of Rigidity

Doctors also look for rigidity (another sign of Parkinson's) by moving the joints in your elbows, wrists, knees, and ankles to see if there's resistance. The resistance may be smooth or may appear as slight hesitations in movements, known as cogwheeling. This is sometimes made more obvious by the patient actively moving the opposite limb.

Evaluating Your Balance

Impaired balance (postural instability) usually occurs later in the disease and is a significant source of disability for patients.

To test for this, your doctor will quickly and firmly pull back on your shoulders while standing behind you. Taking one to two steps backward in order to regain your balance is a normal response, while anything more may indicate a concern.

Checking Your Response to Medication

In an effort to determine if you have Parkinson's disease, your doctor may actually give you a dose of the PD medication carbidopa-levodopa. If you have Parkinson's, you should notice significant improvement, which can confirm the diagnosis.

Imaging

Imaging is not often used in the diagnosis of Parkinson's disease, but such studies may be helpful in some cases.

A magnetic resonance imaging (MRI) scan is one of the more common tests done during a neurologic workup. It isn't particularly helpful in diagnosing Parkinson's disease because the brain structure will appear normal, but MRI can be used to rule out other disorders such as stroke, tumors, hydrocephalus (enlargement of the ventricles) and Wilson’s disease (a disease resulting from copper accumulation that can cause tremors in younger individuals).

If an MRI is done, it's typically in people under age 55 or when the clinical picture isn't typical for Parkinson's.

Specialized imaging gives information on how the brain is functioning rather than its structure.

A DaTscan is a type of single-photon emission computed tomography, or SPECT scan. An agent is injected that highlights the dopamine-producing nerve cells. In Parkinson's disease, there will be less dopamine activity visible.

This can be helpful in differentiating between the effects of Parkinson's disease and conditions such as essential tremor where dopamine levels are normal. But it may not distinguish between Parkinson's and other Parkinsonian syndromes (conditions that cause PD-like movement issues ) such as multiple system atrophy or progressive supranuclear palsy.

Positron emission tomography (PET) scans can help identify different neurodegenerative disorders, such as Parkinson’s disease, as well. They look at how the brain uses glucose; there are specific patterns seen for different disorders. However, they are more often used in research rather than in diagnostic testing.

Differential Diagnoses

Parkinsonism can be caused by other disease processes, including neurodegenerative diseases and secondary causes.

Drugs including antipsychotics, anti-emetics, calcium channel blockers, anti-epileptics, and SSRI anti-depressants can also cause symptoms, though they will usually go away in a few weeks after stopping these medications. Some toxins, including pesticides and carbon monoxide poisoning, can produce Parkinsonism as well.

If dementia develops within the first year of the Parkinsonism, it is characterized as dementia with Lewy bodies. Whenever dementia symptoms are seen so early, the doctor should rule out infection or a subdural hematoma.

Multiple system atrophy also shows Parkinsonism, but it tends to progress rapidly and doesn't respond well to the levodopa medication. An MRI can sometimes help distinguish between this condition and Parkinson's disease.

There are other conditions that produce a tremor, including essential tremor and dystonic tremor. These have characteristics that the neurologist can usually distinguish from Parkinson's disease.

Sometimes the diagnosis will not become clear until after repeated visits to look for the progression of symptoms.

A Word From Verywell

Researchers are working on blood and spinal fluid tests that may be allow your medical provider to make the diagnosis earlier on. In the meantime, don't let the prospect of a long diagnostic process deter you from seeing a doctor. Treatments are available and can help with symptoms as well as with prevention of complications associated with Parkinson's.

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Article Sources

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  1. Greenland JC, Barker RA. The Differential Diagnosis of Parkinson’s Disease. In: Stoker TB, Greenland JC, editors. Parkinson’s Disease: Pathogenesis and Clinical Aspects. Brisbane (AU): Codon Publications; 2018.

  2. National Institute of Neurological Disorders and Stroke. Tremor Fact Sheet. Updated August 13, 2019.

  3. National Institute of Neurological Disorders and Stroke. Parkinson's Disease: Challenges, Progress, and Promise. Updated August 13, 2019.

  4. Kim SD, Allen NE, Canning CG, Fung VS. Postural instability in patients with Parkinson's disease. Epidemiology, pathophysiology and management. CNS Drugs. 2013;27(2):97-112. doi:10.1007/s40263-012-0012-3

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