Parkinson’s disease diagnosis

Making a Parkinson’s disease diagnosis isn’t always easy, especially in the early stages of the disease. Parkinson’s disease can cause symptoms similar to those of many other neurological conditions, and no single test can conclusively confirm a Parkinson’s diagnosis.

How is Parkinson’s disease diagnosed?

If Parkinson’s disease is suspected, the patient will likely need to see a specialist called a neurologist to confirm a diagnosis. The neurologist will review the patient’s medical history and perform motor tests for Parkinson’s symptom assessment. They may order additional tests, such as a levodopa response test or a biomarker test, and order imaging to help support a diagnosis.

Parkinson’s diagnostic criteria

Parkinson’s is defined by four motor symptoms:

• slowed movement (bradykinesia)
• rigidity
• rest tremor
• problems with balance and posture

To be diagnosed with Parkinson’s disease, a person must meet the core diagnostic criteria outlined in the Movement Disorder Society (MDS) guidelines. The individual must have bradykinesia along with at least one of the other three motor symptoms.

According to the MDS criteria, clinicians should rule out other neurological conditions or secondary causes of Parkinson’s-like symptoms before making a diagnosis.

Motor tests

Motor tests for Parkinson’s are important for diagnosis and will typically be performed by a neurologist or movement disorder specialist as part of a physical exam. Motor tests include:

• Bradykinesia tests: The doctor will ask the patient to do a repetitive action, such as tapping their fingers or opening and closing their fists. People with bradykinesia generally have difficulty performing these tasks.
• Rigidity tests: The doctor applies force to move a patient’s limb, usually at the wrist, elbow, or knee, while the limb is at rest. With rigidity, the limb resists movement.
• Tremor tests: A tremor test may involve sitting with hands resting on the knees while the patient performs mental tasks to make the tremor more noticeable. The doctor may then ask the patient to perform actions to observe how the tremor changes. Many people with Parkinson’s have a resting tremor, which lessens or disappears when the affected body parts move.
• Balance tests: These may include walking a certain distance or standing up from a seated position. The doctor may also gently pull at the patient’s shoulders to check balance.

Supportive tests and medication trials

A neurologist may order additional tests alongside the clinical exam to help support a diagnosis of Parkinson’s disease.

Levodopa challenge test

Parkinson’s disease results from the loss of dopamine-producing nerve cells in the brain. Dopamine is a chemical messenger involved in producing smooth, controlled movement. Lack of dopamine signaling in the brain can cause the motor symptoms associated with Parkinson’s.

Levodopa and its derivatives are gold standard medications for Parkinson’s treatment that work to ease motor symptoms by providing the brain with the resources needed to make dopamine.

Testing a levodopa response in a person suspected of having Parkinson’s can help to determine if the individual has Parkinson’s disease or a distinct condition with similar symptoms that levodopa does not treat.

In a levodopa test, levodopa or a similar medication is administered at a high enough dose to show benefit in someone with Parkinson’s (low doses for a day or two aren’t reliable). The doctor and patient will then work together to assess how the patient’s symptoms responded to treatment.

Smell test

Loss of smell, also called olfactory dysfunction or hyposmia, is one of the most common nonmotor symptoms of Parkinson’s disease. People with Parkinson’s may lose their sense of smell for years or decades before other symptoms become apparent.

A smell test may help identify early signs of Parkinson’s and distinguish it from other conditions.

The smell test is not very specific, however. Many people lose taste and smell as they age or due to other conditions, and not everyone who loses these senses develops Parkinson’s.

Cognitive tests

People with Parkinson’s may experience cognitive impairments that affect thinking and memory. Cognitive tests are used to assess thinking ability.

Common tests that assess cognitive function include the Mini-Mental State Examination and the Montreal Cognitive Assessment. Patients may also be referred for neuropsychological testing, a comprehensive cognitive examination that often takes several hours.

Many people with Parkinson’s don’t develop substantial cognitive issues until later stages of the disease. Testing for cognitive problems isn’t needed to confirm a Parkinson’s diagnosis, but it can be valuable for detecting issues early so patients and their families can get support to help manage living with Parkinson’s.

Many people with Parkinson’s disease also have nonmotor symptoms that may be assessed with questionnaires.

Brain imaging and advanced biomarker tests

Other tests that can aid in the diagnosis of Parkinson’s disease include brain imaging scans and biomarker tests:

• Imaging scans: Allow doctors to look at the dopamine system in the brain or check for other conditions that may cause symptoms that mimic Parkinson’s disease
• Biomarker tests: Detect substances associated with Parkinson’s, such as the protein alpha-synuclein

Dopamine transporter scan

A dopamine transporter scan (DaTscan) for Parkinson’s disease may help differentiate Parkinson’s from other conditions with similar symptoms, but it’s not usually required for diagnosis, and most people don’t need one.

DaTscan is a form of single-photon emission computerized tomography that provides a picture of the dopamine-making brain cells whose death and dysfunction cause Parkinson’s.

The U.S. Food and Drug Administration has approved DaTscan to measure dopamine activity in adults with Parkinson’s, although the technology can’t reliably distinguish Parkinson’s disease from other diseases that cause dopamine loss in the brain.

Other imaging tests that may be used during a diagnostic workup for Parkinson’s disease include:

• MRI
• functional MRI
• positron emission tomography scans

These techniques generally aren’t very helpful for diagnosing Parkinson’s, but they may help rule out other conditions.

Alpha-synuclein tests

In Parkinson’s disease, the protein alpha-synuclein misfolds and forms clumps inside brain cells. These clumps are toxic to nerves and are thought to play a central role in the disease.

The following biomarker tests detect these protein clumps and can help support a Parkinson’s diagnosis:

• Alpha-synuclein seed amplification assay: Tests for misfolded alpha-synuclein in cerebrospinal fluid
• Syn-One Test: Uses skin biopsies to look for the presence of alpha-synuclein in nerve fibers in the skin

These tests can’t distinguish Parkinson’s from other disorders marked by alpha-synuclein clumping, such as Lewy body dementia and multiple system atrophy, but they may support a Parkinson’s diagnosis and help determine patient eligibility for clinical trials targeting alpha-synuclein.

Genetic tests

Most cases of Parkinson’s don’t have any clear genetic cause, but about 5% to 10% of people with the condition have a variant in a single gene linked to Parkinson’s disease. These variants are particularly common among people with a family history of the disease and may be linked to early-onset Parkinson’s.

Genetic testing can identify if a person carries a Parkinson’s-related genetic variant. These tests can be complicated to interpret, since some people who carry Parkinson’s-related genetic variants will never develop the disease.

A genetic test is not required to confirm a diagnosis of Parkinson’s disease, but people with a family history of the disease may find it helpful to speak with a genetic counselor and consider getting tested.

For people with Parkinson’s who carry a disease-related variant, genetic testing may help provide clues about their likely prognosis and determine eligibility for clinical trials.

Ruling out alternative conditions

Parkinsonism is an umbrella term for a group of motor symptoms, including slowness of movement, rigidity, and tremor, shared by Parkinson’s disease and a number of other health conditions.

Making a diagnosis of Parkinson’s may involve ruling out other causes of parkinsonism. These include:

Next steps after receiving a Parkinson’s diagnosis

Being diagnosed with Parkinson’s disease can be overwhelming. These steps may help a person with a new Parkinson’s diagnosis to move forward:

• Build a healthcare team of specialists who can help the patient manage symptoms, including a neurologist who specializes in movement disorders, a physical therapist, an occupational therapist, and a speech-language pathologist.
• Consult with a doctor for credible resources to learn more about the diagnosis.
• Start a symptom journal to track symptoms and how they respond to treatment.
• Join an online or in-person support group to connect with others who have the condition.
• Prioritize healthy lifestyle habits, such as exercise, a balanced diet, plenty of sleep, and stress-management techniques.

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Parkinson's News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.