Appendix 1. Parkinson’s Disease and Parkinsonism — What Is the Difference?
— They look alike, but they are not the same disease
The name Parkinson’s disease is familiar.
The hand trembles.
The body stiffens.
Movement slows.
The stride becomes shorter.
But in the clinic or in medical textbooks, another similar-sounding term appears:
parkinsonism.
At first, the two can sound like the same thing.
I also did not initially feel that the distinction was very clear.
But the two terms are not identical.
The most important difference is this:
Parkinson’s disease is one specific disease, while parkinsonism is a clinical term that groups together several conditions that produce similar motor symptoms.
Once this distinction becomes clear, Parkinson’s disease itself also comes into sharper focus.
1. Parkinsonism is a bundle of symptoms
Parkinsonism is not the name of one disease.
It usually refers to a state in which parkinsonian motor features are present, such as:
bradykinesia,
rigidity,
rest tremor,
and postural instability.
In other words, just because a patient looks “slow, stiff, shaky, and unable to walk well” does not mean that the patient necessarily has Parkinson’s disease.
Different diseases with different causes and pathological mechanisms can create similar motor symptoms.
That is why the term parkinsonism is needed.
2. Parkinson’s disease sits inside parkinsonism
Parkinson’s disease is the most representative cause of parkinsonism.
Put simply:
Parkinson’s disease sits inside the larger box called parkinsonism.
Parkinson’s disease is a degenerative disorder mainly associated with the loss of dopamine neurons in the substantia nigra.
As dopamine in the striatum falls, the balance of the basal ganglia circuit breaks down, and symptoms such as bradykinesia, rigidity, tremor, and motor fluctuations can appear.
Most of what we have studied so far in this series has been about this disease — Parkinson’s disease itself.
3. Other diseases can produce similar symptoms
There are diseases that produce parkinsonian motor symptoms without being Parkinson’s disease.
Representative examples include:
multiple system atrophy (MSA),
progressive supranuclear palsy (PSP),
corticobasal syndrome (CBS),
and dementia with Lewy bodies (DLB).
These are often grouped under the term atypical parkinsonism.
They can look similar to Parkinson’s disease on the surface.
But over time, characteristic features of each disorder begin to emerge.
4. Why is it difficult to distinguish them at first?
Because the symptoms often overlap early in the disease.
Imagine a patient who has become slower, has stiffness on one side, and has developed a shorter stride.
That patient may have Parkinson’s disease, but another parkinsonian disorder is also possible.
Especially early on, the characteristic signs of each disease may not yet be fully developed.
That is why diagnosing Parkinson’s disease is not always something that can be completed with a single test or a single visit.
Watching how the symptoms evolve over time and how they respond to medication is an important part of the diagnostic process.
5. Parkinson’s disease often begins asymmetrically
One of the typical features of Parkinson’s disease is asymmetry.
One hand may slow first.
The arm swing on one side may decrease.
One leg may begin to drag before the other.
Even after symptoms eventually affect both sides, the side where the disease began often remains more severely affected.
Some atypical parkinsonian disorders, by contrast, may begin more symmetrically or become symmetric relatively quickly.
This distinction is not absolute, but it can help with the differential diagnosis.
6. The levodopa response is a very important clue
One of the most important clinical features of Parkinson’s disease is its response to levodopa.
In typical Parkinson’s disease, bradykinesia, rigidity, and at least some tremor may improve substantially with levodopa.
Patients often notice a clear change:
“My body loosens up after I take the medication.”
In atypical parkinsonism, the levodopa response is often weaker or more short-lived.
There are exceptions, of course.
Some patients may show a partial response early on.
So simply saying “the medication helped a little” is not enough.
What matters is:
how clearly the symptoms improve, how long the benefit lasts, and which symptoms respond.
7. Motor fluctuations can become a characteristic feature of Parkinson’s disease
Over years of Parkinson’s disease, medication-response patterns such as:
wearing-off,
delayed ON,
ON–OFF fluctuation,
and dyskinesia
may emerge.
This also means that there is still a neural circuit capable of responding substantially to dopaminergic medication.
In parkinsonian disorders that respond very little to levodopa, this typical medication-effect curve may be much less obvious.
That difference can also provide a diagnostic clue.
8. Frequent early falls suggest another possibility
Patients with typical Parkinson’s disease can eventually develop balance problems and falls as the disease progresses.
But repeated, severe falls very early in the course deserve a different kind of attention.
In progressive supranuclear palsy (PSP), postural instability and falls can become prominent early.
So the story:
“I have parkinsonian symptoms, but I started falling backward repeatedly very early,”
is an important clue.
9. Abnormal eye movements are an important signal
In progressive supranuclear palsy, eye movements — especially vertical eye movements — can become impaired.
A patient may have difficulty looking downward, going down stairs, or directing the gaze toward food.
Parkinson’s disease can also produce several ocular-motor abnormalities, but a characteristic vertical gaze abnormality strongly raises the possibility of PSP.
10. When autonomic symptoms are too early and too severe
Autonomic symptoms such as orthostatic hypotension, constipation, and bladder dysfunction are also common in Parkinson’s disease.
But when severe orthostatic hypotension or urinary dysfunction appears very early in the disease, multiple system atrophy (MSA) becomes an important consideration.
In MSA, autonomic nervous system failure is a major part of the disease along with the motor disorder.
So the same complaints —
“My bladder is difficult to control,”
or
“I get dizzy when I stand up” —
mean something different depending on when they began and how severe they became.
11. When one limb feels as if it is not your own
Corticobasal syndrome (CBS) can produce very distinctive symptoms.
One limb may become severely rigid.
Apraxia may appear.
The ability to integrate sensory information may be impaired.
At times, the hand may seem to move on its own, producing the so-called alien limb phenomenon — the feeling that “this hand is not really mine.”
These cortical features point in a direction that is different from typical Parkinson’s disease.
12. When cognition and visual hallucinations are prominent early
In dementia with Lewy bodies (DLB), cognitive changes and visual hallucinations are important features.
Attention and alertness may fluctuate significantly over time, and well-formed visual hallucinations can occur.
Motor parkinsonism can also be present.
Parkinson’s disease itself can produce cognitive impairment and hallucinations later in the disease, but when these symptoms appear very near the onset of motor symptoms, DLB becomes an important consideration.
13. Looking for red flags
When distinguishing Parkinson’s disease from atypical parkinsonism, clinicians look for specific red flags.
Examples include:
early recurrent falls,
rapid disease progression,
severe early autonomic failure,
vertical gaze abnormalities,
prominent cerebellar signs,
severe early speech or swallowing problems,
early cognitive or behavioral changes,
and severe parkinsonism with very little response to levodopa.
The presence of one of these signs does not immediately establish a specific diagnosis.
But it is an important signal that:
“This may not look like typical Parkinson’s disease.”
14. Imaging does not provide every answer
Patients often assume that one MRI, PET scan, or dopamine-related imaging study can distinguish every disease precisely.
In practice, the diagnosis is not that simple.
MRI can help rule out other structural diseases or reveal findings that suggest certain atypical disorders.
Dopaminergic imaging can help show whether there is degeneration of the dopaminergic system.
But one test does not always allow us to say with certainty:
“This is Parkinson’s disease, and that is MSA.”
In the end, what matters is putting together:
**how the symptoms began,
the speed of progression,
the neurological examination,
the levodopa response,
non-motor symptoms,
imaging findings,
and change over time.**
15. Why does this distinction matter?
The goal is not merely to attach the correct disease label.
Treatment and prognosis differ.
Typical Parkinson’s disease often responds well to levodopa, and DBS can become an important treatment option in appropriately selected patients.
Some atypical parkinsonian disorders respond only modestly to levodopa, and DBS is generally not expected to provide the same benefit.
Some disorders require especially careful management of autonomic failure.
Others require early attention to falls or swallowing problems.
So an accurate distinction can directly change the treatment plan.
16. Studying parkinsonism makes Parkinson’s disease clearer
As I studied the different forms of parkinsonism again, the features of Parkinson’s disease itself became easier to see.
Why does Parkinson’s disease so often begin on one side?
Why does levodopa responsiveness matter so much?
Why can gait and balance be relatively preserved early in the disease?
Why do motor fluctuations and dyskinesia become such important problems over many years?
These features become much more visible when Parkinson’s disease is compared with the other disorders.
The easiest way to distinguish Parkinson’s disease from parkinsonism
Put very simply:
Parkinson’s disease
is one specific degenerative disease that produces parkinsonian symptoms.
Parkinsonism
is an umbrella term for the group of diseases and conditions that produce parkinsonian motor symptoms, including Parkinson’s disease itself.
So:
Parkinson’s disease is a form of parkinsonism, but not all parkinsonism is Parkinson’s disease.
Remembering that one sentence resolves most of the confusion between the two terms.
Rethinking Parkinson’s disease through my own body
Living with Parkinson’s disease for a long time makes you sensitive to every symptom.
Walking.
Tremor.
Rigidity.
Medication response.
Dyskinesia.
Autonomic symptoms.
At first, I thought all of these simply appeared in the same way under one disease name — Parkinson’s disease.
But after studying the other forms of parkinsonism, my view changed.
Two patients can look similarly slow, similarly stiff, and similarly unable to walk well, while the circuits failing underneath and the way the disease progresses are very different.
So what matters is not simply how similar the symptoms look on the surface, but in what sequence they appear and within what pattern of circuit change they develop.
And once I saw those differences, the Parkinson’s disease I had experienced in my own body also became easier to recognize.
Appendix 1 in one line
Parkinson’s disease is one specific neurodegenerative disorder, while parkinsonism is an umbrella term for the range of diseases and conditions — including Parkinson’s disease — that produce parkinsonian symptoms such as bradykinesia, rigidity, and tremor.