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How a Diagnosis is Made

The bedside examination by a neurologist remains the first and most important diagnostic tool for Parkinson’s disease (PD). Researchers are working to develop a standard biological marker such as a blood test or an imaging scan that is sensitive and specific for Parkinson’s disease.

A neurologist will make the diagnosis based on:

  • A detailed history of symptoms, medical problems, current and past medications. Certain medical conditions, as well as some medications, can cause symptoms similar to Parkinson’s.
  • A detailed neurological examination during which a neurologist will ask you to perform tasks to assess the agility of arms and legs, muscle tone, gait and balance, to see if:
    • Expression and speech are animated.
    • Tremor Involuntary shaking of the hands, arms, legs, jaw or tongue. The typical Parkinson’s tremor is “pill-rolling” – it looks like holding a pill between thumb and forefinger and continuously rolling it around. Some people report an internal tremor, a shaking sensation inside the chest, abdomen or limbs that cannot be seen. Most Parkinson’s tremor is “resting tremor,” which lessens during sleep and when the body part is actively in use. can be observed in your extremities at rest or in action.
    • There is stiffness in extremities or neck.
    • You can maintain your balance and examine your posture.
  • You may notice that a neurologist records your exam into a table, called Unified Parkinson’s Disease Rating Scale (UPDRS). This is a universal scale used by neurologists and movement disorder specialists Neurologists with extra training (usually a one- or two-year fellowship) in Parkinson’s and other movement disorders. to comprehensively assess and document the exam of a person with PD at a baseline, judge the effect of medication and track the progression of disease during future visits.
  • Most commonly, people with PD respond well to dopaminergic medications. Lack of response to medications may prompt the doctor to seek an alternative diagnosis such as atypical parkinsonism A group of brain disorders that initially look like Parkinson's disease, but differ in the course of the disease and response to antiparkinson medications. The term is used interchangeably with Parkinson-plus syndromes. and order further testing such as an MRI (magnetic resonance imaging) A medical imaging technique that uses magnetic forces to obtain detailed images of the body. MRI is non-invasive and does not use radiation. of the brain.
  •  When unsure of a PD diagnosis, neurologists often refer patients to movement disorders specialists and order DAT scans.

What is a DAT scan and what role does it play in a Parkinson’s diagnosis?

A DAT scan is an imaging technology that uses small amounts of a radioactive drug to help determine how much dopamine A chemical messenger (neurotransmitter) that regulates movement and emotions. is available in a person's brain. A SPECT scanner is used to measure the amount and location of the drug in the brain.

In 2011, the U.S. Food and Drug Administration (FDA) approved the use of a DAT scan.

While a DAT scan cannot diagnose PD, doctors use them to confirm a diagnosis. A negative DAT scan result does not rule out a Parkinson’s diagnosis, but a positive result helps confirm it. The problem with positive results is that it does not differentiate Parkinson’s disease from other forms of parkinsonism, such as multiple system atrophy (MSA) or progressive supranuclear palsy (PSP), that can also produce a loss of dopamine in the brain. A positive DAT scan can differentiate PD from Essential Tremor A nervous system disorder that causes shaking of the hands or head and an unsteady quality of the voice. Shaking usually occurs on both sides of the body (compared to Parkinson’s, in which tremor typically begins on one side only) and is worse during movement (compared to Parkinson’s resting tremor). Essential tremor is more common than Parkinson’s. (ET) as there is no dopamine deficiency in the latter.


Are there risks associated with DAT scan?
Possible adverse reactions such as headache, nausea, vertigo, dry mouth and mild to moderate dizziness were reported, hypersensitivity reaction and injection site pain have also been reported.

I have PD and several symptoms. Should I get a DAT scan?
Likely no. There is no need for DAT scan when your history and exam suggests Parkinson’s disease and you meet the diagnostic criteria. Occasionally, if signs and symptoms are mild or you don’t meet the diagnostic criteria then your neurologist or movement disorder specialist will refer you for a DAT scan. Keep in mind that ultimately the diagnosis is based on your history and physical exam and the DAT scan is most commonly used to complete the picture and is not a necessary test for a diagnosis.

How can I get a DAT scan?
Speak with your doctor to see if a DAT scan is right for you. Learn more about DAT scans at

Is the DAT scan test covered by insurance, Medicare and Medicaid?
A DAT scan is covered by Medicare and Medicaid. Insurers are likely to cover a DAT scan, but coverage varies so please contact your insurer for confirmation before the procedure.

The Parkinson’s Foundation recommends that a person with symptoms resembling those of PD consider making an appointment with a movement disorder specialist. To find a specialist in your community, call our free Helpline at 1-800-4PD-INFO (473-4636) from Monday to Friday, 9:00 AM ET to 5:00 PM ET.

Page reviewed by Dr. Ahmad Elkouzi, Movement Disorders Fellow at the University of Florida, a Parkinson’s Foundation Center of Excellence.

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