How Parkinson's Disease Is Diagnosed

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There's no "gold standard" test that will diagnose Parkinson's disease—instead, physicians rely on their own clinical observation and judgment along with the patient's description of possible signs and symptoms in order to make the diagnosis. That, of course, makes a physical examination very important in the diagnosis process. Much of your doctor's examination will be aimed at assessing whether you have the so-called cardinal signs of Parkinson's: resting tremor, bradykinesia (slowness of movement) and postural instability (impaired balance). Here's how doctors often look for these signs.

Self-Checks/At-Home Testing

Make note of any symptoms you have been experiencing that are of concern. These include tremor, rigidity, and impaired balance. But because Parkinson's disease affects the nerves to organs throughout your body, it can result in a variety of other symptoms. 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

Labs and Tests

A trip to the neurologist’s office often includes what seems like dozens of questions, along with multiple tests. Your blood pressure will be taken sitting and standing to look for orthostatic hypotension. 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.

The movement disorder specialist will do a variety of physical tests to assess you. Knowing what your doctor is looking for in these tests may help make the diagnostic process a bit easier.

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—in other words, when you're resting. 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. She may also look for kinetic tremor, which occurs with voluntary movement and is usually assessed by the finger-to-nose test (where the patient touches their nose with their index finger and then touches 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 these different types of tremors.

Slowness of Movement

This Parkinson's disease symptom, called "bradykinesia" by doctors, occurs in most people who have the condition. It may cause a lack of spontaneous facial expressions 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 the 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.

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.

Impaired Balance Appears Late in Parkinson's

Impaired balance (what doctors call "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 the presence of this debilitating symptom.

Responsiveness to Parkinson's Medications

Your doctor may give you a dose of carbidopa-levodopa and look for your response. If you have Parkinson's disease, you should have significant improvement and this can confirm your diagnosis.

Imaging

Imaging tests are often not used in the diagnosis of Parkinson's disease but may be if the clinical picture is unclear.

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 as the brain structure will appear normal. It may be done for someone under age 55 or when the clinical picture isn't typical for Parkinson's disease. An MRI can be used to rule out other disorders such as stroke, tumors, hydrocephalus (swelling in the brain) and Wilson’s Disease (a disease resulting from copper accumulation that can cause tremors in younger individuals).

Specialized imaging such as PET scans and DaTscans give information on how the brain is functioning rather than its structure. In a DaTscan, 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 parkinsonisms such as multiple system atrophy or progressive supranuclear palsy.

PET scans can help identify different neurodegenerative disorders such as Parkinson’s disease. They look at how the brain uses glucose, and 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.

Parkinsonism can be caused by drugs including antipsychotics, anti-emetics, calcium channel blockers, anti-epileptics, and SSRI anti-depressants. The symptoms will usually go away in a few weeks after stopping these medications. Some toxins, including pesticides and carbon monoxide poisoning, can produce parkinsonism.

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 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

It can be scary to make an appointment with a neurologist to be tested for Parkinson's disease. But it is far better to see a specialist sooner rather than later. Early treatment can help prevent or delay the complications and progression of the condition. Researchers are working on blood and spinal fluid tests that may be able to make the diagnosis earlier so patients can benefit from early treatment.

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Article Sources

  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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