The terms parkinsonism, Parkinson disorder, and Parkinson syndrome are all synonymous and can be used interchangeably depending on which you prefer. All of these terms refer to the symptoms. To be diagnosed with a Parkinson disorder, you must exhibit two out of three of the following motor symptoms:
- unilateral resting tremor
- slowness of movement (bradykinesia)
- muscle rigidity or stiffness (cogwheel rigidity)
This is with or without postural instability, which usually refers to a shuffling gait, poor balance, and increased falls.
When someone gets symptoms of parkinsonism, they often think they have Parkinson disease because of its popularity in famous people like Muhammad Ali and Michael J. Fox. However, there are more Parkinson disorders than just Parkinson disease, and these rarely get shown on TV or other forms of media. There are three main categories of Parkinson disorders: typical, atypical, and secondary Parkinson disorders. Only Parkinson disease is in the typical category, and it responds to 200 mg of carbidopa/levodopa (a Parkinson disease medication also called Sinemet) by at least 30 percent.
There are several Parkinson disorders in the atypical category, and the most frequently occurring ones are Lewy body dementia, multiple system atrophy, and progressive supranuclear palsy. Remember there are many more Parkinson disorders and disorders that have symptoms of parkinsonism as an extra feature. The world started to know more about atypical Parkinson disorders when famous comedian Robin Williams developed Lewy body dementia, although the news outlets mistakenly announced it was Parkinson disease initially. Secondary parkinsonism can be caused by brain tumors, normal pressure hydrocephalus (increased fluid in the brain), prescription medications, pesticides, organic solvents, industrial chemicals, and herbicides like Agent Orange.
The rarity and reality of PSP
Progressive supranuclear palsy, or PSP, is rare and occurs in three to 10 per 100,000 people, mainly occurring in those over 60 years of age and affecting 20,000 to 40,000 Americans. Former Representative Jennifer Wexton’s battle with progressive supranuclear palsy led to the passing of the National Plan to End Parkinson’s Act (H.R. 2365) in 2024. Even then, instead of parkinsonism, Parkinson disorders, or Parkinson syndrome being in the title of the bill, it was “Parkinson’s,” which is what people say when referring to Parkinson disease. Recently, Jesse Jackson was diagnosed with Parkinson disease in 2017, then progressive supranuclear palsy in April 2025.
Common reasons for misdiagnosis
Why might Jesse Jackson or any other patient be misdiagnosed with Parkinson disease instead of PSP? Here are the most common reasons that people are misdiagnosed with Parkinson disease instead of an atypical or secondary Parkinson disorder. The public and primary care physicians are sometimes unaware of subspecialties that neurologists receive only brief exposure to in residency, assuming that just being a smart neurologist is good enough. However, intelligence does not make a well-trained subspecialist. Therefore, most people will see a general neurologist or a neurologist whose specialty is not movement disorders.
Finding the right specialist
Who should people see if they think they have a Parkinson disorder? They should see a neurologist with fellowship training in movement disorders. Be warned that since there is not a subspecialty board exam for movement disorders, any neurologist can say they specialize in it or are a movement disorder specialist. What you want to do is ask the neurologist’s staff or research them online to see if they have done a fellowship in movement disorders. These neurologists read movement disorder journals, attend movement disorder conferences, and stay up with the most current research, just like any other subspecialty in neurology.
Differentiating PSP from Parkinson disease
What can you look for early on to differentiate PSP and Parkinson disease? In all atypical Parkinson disorders, there is a more rapid progression of motor symptoms than in Parkinson disease, and the motor symptoms respond less than 30 percent to 200 mg of carbidopa/levodopa. Even though atypical Parkinson disorders have symptoms that overlap, they also have additional symptoms that can help you distinguish them.
In PSP, there are usually multiple falls per day in the first one to two years, which can easily be in the double digits. Furthermore, the eyes can have the inability to look up or down. There is also early cognitive decline leading to dementia and behavioral changes in PSP in the first two years, which does not occur until 10 years in Parkinson disease. People with PSP can also have significant difficulty speaking (dysarthria) in the first two years.
Since medications often do not significantly improve motor symptoms, physical and occupational therapy and exercise are usually prescribed and can improve motor symptoms. The non-motor symptoms like dementia and behavioral changes, such as depression, agitation, physical aggression, or anxiety, can be treated with medications. The speech difficulties are usually treated by speech therapy.
Jerome Lisk is a neurologist.
