How Do You Test for Parkinson’s Disease? An In-Depth Look at How It’s Diagnosed

Parkinson’s disease (PD) is a neurologic condition characterized by a resting tremor, slowed movements, instability, and rigidity. Unfortunately, these symptoms aren’t specific to Parkinson’s and sometimes overlap with other diseases. And there isn’t a blood or imaging test for it, so diagnosing Parkinson’s can be tricky. 

Parkinson’s disease is caused by a loss of certain cells in your brain, known as neurons, that use a molecule called dopamine to send messages to each other. The only sure way to diagnose Parkinson’s is actually during an autopsy. But correct early diagnosis is important since it will help with getting the right treatment and prognosis of the disease. Here we’ll discuss the process of testing and diagnosing Parkinson’s disease. 

Can you test for Parkinson’s disease? 

There’s no test that can diagnose Parkinson’s disease. So healthcare professionals — usually a neurologist — largely rely on what’s called a “clinical diagnosis.” This means that the diagnosis is based on symptoms and physical examination. 

Usually there are enough clues that allow a neurologist to correctly diagnose Parkinson’s. But sometimes it’s helpful to get other tests to confirm the diagnosis (more on this below). As medical tests get more advanced, there may be a better test in the future that’s more specific to Parkinson’s disease.

How is Parkinson’s disease diagnosed?

Usually the diagnosis journey starts when you or a loved one notice symptoms that may be concerning. For example, it might be a tremor or an abnormal movement pattern that makes you look for medical advice. 

When you first go to see your regular healthcare professional, they’ll likely refer you to a neurologist or a movement disorder specialist. They’re the experts at diagnosing Parkinson’s, especially since it’s a clinical diagnosis. 

They’ll start by asking a lot of questions about the symptoms and how they might have changed over time. For example, did the tremor start in one hand initially then move to both hands? Or did you notice it in both hands from the start? 

Your neurologist will also perform a physical exam, looking for tremors, and your body’s movement patterns. The main hallmarks of the disease that help in diagnosis are:

• Tremor, or shaking, at rest

• Slowed movements, also known as bradykinesia

• Stiffness and rigidity

• Poor balance

• Difficulty walking
  

In the process, the neurologist will also rule out other diseases or conditions that can cause similar symptoms. These include strokes, essential tremor, and inner-ear issues that cause poor balance. If you have the hallmark symptoms of PD, and your neurologist doesn’t think there’s another cause of your symptoms, they may diagnose you based on that alone. 

What tests help confirm Parkinson’s disease? 

If symptoms and signs on physical examination are enough to make a diagnosis, further testing isn’t necessary. But there are a few tests that can be helpful if the clinical diagnosis is less clear.

DaT/SPECT scan

DaT scans — also known as SPECT scans, or dopamine transporter imaging — look at those dopamine neurons in the brain. Since Parkinson’s is caused by the degeneration of those neurons, a DaT scan can help in diagnosis. 

Some other diseases like multiple system atrophy (MSA) or progressive nuclear palsy (PSP) can look similar to Parkinson’s on a DaT scan. A DaT scan is the most commonly used imaging test to help confirm a diagnosis of PD. But its accuracy in diagnosis is virtually equal to using just clinical diagnosis alone, so it’s not used in all cases.

MRI

MRI or other brain imaging is not recommended for routine diagnosis of Parkinson’s. It’s only used when symptoms aren’t typical or overlap with other diseases. MRI can help diagnose things like a stroke or a brain tumor, so it can help rule out other potential causes of symptoms. As MRI imaging techniques get more advanced, it’s possible that MRI will be used more frequently in the diagnosis of Parkinson’s disease. 

‘Drug challenge’

Because PD is caused by too little dopamine, taking medications that increase dopamine in the brain should improve symptoms. This is the reason behind  a “drug challenge,” which can help confirm a PD diagnosis in some situations. In other words, if your symptoms get better with a medication that increases dopamine, Parkinson’s is likely the right diagnosis. If symptoms don’t get better with these medications, it’s very likely that PD isn’t the right diagnosis. 

Olfactory testing

More than 95% of people with Parkinson’s disease develop issues with smelling. “Olfactory testing” is a fancy name for a smell test. This is also not specific for PD, so it’s not very useful. As such, this test is rarely used.

And keep in mind that people develop these symptoms at different times during the disease. Just because you don’t have any issues with smell now doesn’t mean you don’t have Parkinson’s disease, or that you won’t develop problems with smelling later on. It’s just information that goes along with the bigger picture in your diagnosis. 

Genetic testing

Genetic testing is an option, as Parkinson’s has been linked to some mutations. But fewer than 5% of people with it have an identifiable mutation. This means that most people with the disease will have a negative genetic test. 

Genetic testing can be helpful if PD runs in your family. So if this is true for you, ask your healthcare professional about genetic testing. If you don’t have a family history, a genetic test isn’t necessary for diagnosis. 

How long can you have Parkinson’s without knowing? 

Parkinson’s disease can be a tricky condition to recognize. In the beginning of the disease, symptoms can be mild, and they can look like symptoms of other conditions. For example, the tremor is usually minor, and starts on just one side of your body. This makes diagnosis difficult. As the disease progresses, symptoms become more advanced — like the tremor affecting both sides of your body. This makes the diagnosis not just more obvious but more accurate, too. 

There isn’t a specific amount of time someone can start to show symptoms before diagnosis since everyone’s symptoms are different. If you’re concerned, talk with your healthcare professional about your symptoms. It’s never too early to start the path to diagnosis.

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Written by:

Nicole Andonian, MD

Nicole Andonian, MD, is a private practice anesthesiologist in Orange County, California. Her focus is in general anesthesia, regional anesthesia, and acute pain management.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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