Difference Between Parkinsonism and Parkinson’s Disease in ICD-10-CM

Parkinsonism and Parkinson's Disease in ICD-10-CM
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** This article was reviewed and updated on February 26, 2024. **

Parkinsonism and Parkinson's Disease ICD-10-CM

Parkinsonism and Parkinson’s disease often share symptoms that can cause confusion, but they are distinct conditions with differing underlying causes. This article aims to shed light on the differences between these two conditions and the challenges physicians face when distinguishing between them, especially in the early stages of the disease. Surprisingly, around 10 to 15 percent of initially suspected Parkinson’s disease cases turn out to be atypical parkinsonism disorders, each having a unique etiology unrelated to Parkinson’s disease. Understanding these distinctions is vital for accurate medical coding. Before exploring the differences and the ICD-10-CM coding for these conditions, including the new codes that took effect October 1, 2023, for FY 2024, let’s begin by sharing a personal story of someone dealing with Parkinson’s disease.

Bill’s Personal Journey

Bill’s experience serves as a starting point. Roughly a year ago, he noticed sporadic tremors in his right thumb and fingers, particularly after physical activities. These tremors occurred even at rest. Alongside this, he faced challenges like depression, leg stiffness in the mornings, a hoarse voice in the afternoons, and smaller handwriting. After consulting multiple specialists, including movement disorder experts, Bill received a Parkinson’s disease diagnosis.

Bill’s journey illustrates the complexities and uncertainties that come with this condition. Despite his inquiries, definitive confirmation required an invasive approach, leading to his commitment to managing the disease through prescribed medications (carbidopa and levodopa). The combination of these drugs came with plenty of side effects, such as brain fog, burning in the chest and abdomen, and worsening depression. The physicians had to adjust the dosage a few times before it became tolerable.

Understanding Parkinsonism 

Parkinsonism is a broad term encompassing various neurological conditions characterized by motor symptoms, including tremors (involuntary shaking), mostly at rest, involving the hands, arms, legs, tongue, or jaw, limb rigidity (stiffness or tightness in the arms or legs), bradykinesia (slow movement), and postural instability (loss of balance). According to the Parkinson’s Foundation, these symptoms overlap with those seen in Parkinson’s disease but can also stem from other causes, like vascular disorders.

There are two main categories of Parkinsonism: primary and secondary.

Primary Parkinsonism

Two main groups stand out within primary parkinsonism: Parkinson’s disease and atypical parkinsonism disorders.

Parkinson’s Disease

Parkinson’s disease, the most common form of parkinsonism, remains puzzling in terms of its precise cause. Though scientists believe genetic and environmental factors are at play, a definitive etiology is still unknown. Risk factors include exposure to certain toxins and age, particularly in men over 60. The presence of Lewy bodies and abnormal protein clumps containing alpha-synuclein is observed in the brain cells of many Parkinson’s patients.

As Parkinson’s disease advances, the nerve cells in the basal ganglia, responsible for movement control, deteriorate, giving rise to noticeable symptoms. The underlying reasons for the decline of dopamine-producing brain cells remain uncertain, leading to insufficient dopamine production and worsening motor issues.

Symptoms of Parkinson’s Disease 

Parkinson’s disease primarily manifests through motor symptoms such as tremors at rest, bradykinesia, and limb rigidity. Balance problems tend to emerge later in the disease course. Unique symptoms like a soft voice, small handwriting, and involuntary facial or limb movements may also occur. Depression and non-motor symptoms like cognitive changes, depression, anxiety, and sleep disturbances are common. Bill’s story mirrors these motor and non-motor symptoms.

Secondary parkinsonism comes with its own set of symptoms, including dyskinesia, slurred speech, muscle cramping, and gait issues.

Therapeutic Approaches

The primary line of treatment involves dopaminergic therapy, often in the form of levodopa. This treatment is effective in Parkinson’s and some forms of parkinsonism, though the response may vary.

It is noteworthy that PD medications (levodopa and dopamine agonists) can lead to complications, such as motor fluctuations and dyskinesia, driving the expansion of ICD-10-CM codes for FY 2024. In fact, many PD patients experience motor fluctuations as their disease progresses.

Motor fluctuations, known as “on-off” times, refer to variations in an individual’s ability to move. During “on” time, when medication is effective, the patient experiences improved symptom control and can move and function well. However, as the medication’s effectiveness diminishes, known as “wearing off,” more pronounced symptoms may arise, leading to decreased control over movements, or “off” time. Individuals can also experience dyskinesias (involuntary movements) when medication levels are at their highest points. These changes throughout the day are referred to as motor fluctuations.

When these complications occur, the physician may need to consider a change in medication dosage, add a different one, or consider a surgical option like deep brain stimulation.  

Exploring Atypical Parkinsonism Disorders 

Atypical Parkinsonism embraces a realm of disorders that mirror some core symptoms of Parkinson’s disease but also introduce unique features. According to Johns Hopkins Medicine, these disorders, categorized as “Parkinson’s plus syndromes,” often bring additional challenges like speech and swallowing difficulties and such psychiatric disturbances as agitation, anxiety, or depression. 

Many people do not present with the cardinal symptoms necessary to make a diagnosis of a specific Parkinson’s plus syndrome. Therefore, “parkinsonism” will be the diagnosis given.

There are several different types of atypical Parkinsonism/Parkinson’s plus syndromes, but some have not yet been defined or named. These syndromes generally are more difficult to treat than Parkinson’s disease, and their symptoms may progress more quickly than they do in Parkinson’s disease. Also, Parkinson’s plus syndromes respond minimally, if at all, to levodopa or other Parkinson’s medications.

Following are descriptions and unique characteristics of the most common atypical syndromes.

Progressive Supranuclear Palsy (PSP)

Progressive Supranuclear Palsy, also called Lou Gehrig disease, is the most common form of atypical parkinsonism and is slightly more common than Amyotrophic Lateral Sclerosis (ALS). PSP is a protein buildup affecting the frontal lobes, brainstem, cerebellum, and substantia nigra. 

Symptoms usually begin in the early 60s and include balance problems with frequent falls, forgetfulness, vision problems, including vertical gaze palsy, and changes in personality. Unlike Parkinson’s disease, PSP is not usually associated with tremor.

Dementia with Lewy Bodies (DLB)

The most common type of dementia in the elderly after Alzheimer’s disease, Dementia with Lewy bodies, is characterized by an abnormal accumulation of alpha-synuclein protein in the brain cells called synucleinopathy. DLB causes progressive intellectual and functional deterioration. 

Key symptoms include cognitive decline, signs and symptoms of Parkinson’s disease, with only a slight tremor, if any, and visual hallucinations. 

Multiple System Atrophy (MSA)

Multiple System Atrophy is a term for several neurodegenerative disorders that cause multiple body systems to degenerate. MSA is another synucleinopathy that affects the part of the nervous system that controls such functions as heartbeat, blood pressure, urination, digestion, substantia nigra, and sometimes the cerebellum. 

MSA is the second most common form of atypical parkinsonism and is also known as Shy-Drager syndrome when orthostatic hypotension (low blood pressure upon standing) is prominent. When lying down, blood pressure can be high. Other key symptoms include early sexual, bladder, and bowel dysfunction; impaired speech; breathing and swallowing problems; and inability to sweat.

Corticobasal Syndrome (CBS)

The rarest type of atypical parkinsonism, CBS, usually develops after 60 years of age. CBS usually affects one side of the body more than the other, resulting in problems with the patient’s vision and ability to navigate through space. Corticobasal Syndrome is also known as Corticobasal Degeneration (CBD) or Cortical Basal Ganglionic Degeneration (CBGD).  

Other symptoms may include dystonia (abnormal posture of the limbs) and myocionus (sudden jerking), basic math difficulties, and inability to demonstrate or recognize the use of common objects. An unusual symptom of CBS is the alien limb phenomenon, in which the patient views their arm or leg as a foreign object they have no control over.

Unraveling Secondary Parkinsonism

Secondary parkinsonism includes many different types with varying causes. The two main types of secondary parkinsonism are drug-induced parkinsonism and vascular parkinsonism. 

Drug-Induced Parkinsonism

Parkinsonism can occur as a side effect of certain medications, such as antipsychotics, which interfere with dopamine levels in the brain. This is referred to as drug-induced parkinsonism and can be difficult to distinguish from Parkinson’s.

Key features include parkinsonism symptoms, such as tremors and postural instability, which may be less severe than Parkinson’s disease. The symptoms tend to subside gradually once the causative drug is discontinued.

Vascular Parkinsonism (VP)

Vascular parkinsonism is a common cause of atypical parkinsonism and is typically associated with multiple small strokes that lead to reduced blood flow in the brain. The disorder progresses quite slowly compared to other types of parkinsonism.

Key Features include symptoms that often manifest in the lower extremities, including gait and balance problems with falls. Additionally, symptoms may begin abruptly and worsen before plateauing for a while. 

Other Secondary Causes of Parkinsonism

Parkinsonism may also be caused by metabolic, endocrine, and infectious diseases, toxins, head trauma, and abnormal protein clumps called Lewy bodies, mainly alpha-synuclein.

Parkinsonism and Parkinson's Disease in ICD-10-CM

Diagnosis and Treatment

Diagnosing parkinsonism and Parkinson’s disease lacks a definitive test. Specialists rely on medical history and movement tests to make informed decisions. However, certain tests such as magnetic resonance imaging (MRI) of the brain, a dopamine transporter scan (DaTscan), or blood work can confirm a diagnosis of PD or rule out other similar conditions that resemble PD.

Treatment predominantly revolves around dopaminergic therapy, with levodopa playing a key role. However, treating Parkinson’s plus syndromes proves more challenging and often yields minimal response to standard Parkinson’s medications.

It is not unusual for a physician to change the diagnosis as the disease progresses and according to how the patient responds to medications and other factors.

Complications of long-term use of levodopa resulting in motor fluctuations and dyskinesia can be managed through a change in dosage and timing of the medication or by adding a different therapy. 

Coding for Parkinsonism and Parkinson’s Disease (ICD-10-CM)

Codes for primary (PD and atypical parkinsonism) and secondary parkinsonism are located in Chapter 6. Diseases of the nervous system (G00-G99), mostly within Extrapyramidal and movement disorders (G20-G26). Still, other parkinsonism codes are listed under Other degenerative diseases of the nervous system (G30-G32) and Other disorders of the nervous system (G89-G99). 

Parkinson’s Disease

Currently, one ICD-10-CM code for PD exists, G20. This code is nonspecific and does not capture motor fluctuations and dyskinesias that emerge as PD advances. Therefore, effective October 1, 2023, code G20 will become category G20.- (Parkinson’s disease) and expand into three new subcategories and five new codes.  

According to the CMS, coders can expect to see the following under category G20.- in the upcoming 2024 ICD-10-CM Tabular List:

Parkinsonism and Parkinson's Disease in ICD-10-CM

Note: The inclusion term, Parkinsonism or Parkinson’s disease NOS, is no longer listed under Category G20.-.

Before making your final code selection, be sure to review the coding guidelines and conventions. For example, as the ICD-10-CM Official Guidelines for Coding and Reporting FY 2024 indicates in Section I.A.13. Etiology/manifestation convention (“code first,” “use additional code” and “in diseases classified elsewhere” notes),

“Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first, if applicable, followed by the manifestation.

Wherever such a combination exists, there is a “use additional code” note at the etiology code and a “code first” note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.”The guidelines also indicate (with changes in bold print), “… An example of the etiology/manifestation convention is dementia with Parkinson’s disease. In the Alphabetic Index, a code from category G20 is listed first, followed by code F02.80 or F02.81- in brackets.

A code from category G20- represents the underlying etiology, Parkinson’s disease, and must be sequenced first, whereas codes F02.80 and F02.81- represent the manifestation of dementia in diseases classified elsewhere, with or without behavioral disturbance.”

Atypical Parkinsonism 

The most common atypical syndromes are reported as follows:

  • G23.1, Progressive supranuclear ophthalmoplegia [Steele-Richardson-Olszewski]
    Progressive supranuclear palsy 
  • G31.83, Neurocognitive disorder with Lewy bodies
      Lewy body dementia
    Lewy body disease
  • G31.85, Corticobasal degeneration
  • G90.3, Multi-system degeneration of the autonomic nervous system
      Neurogenic orthostatic hypotension [Shy-Drager]

Secondary Parkinsonism

Secondary parkinsonism codes, including the two main types (drug-induced and vascular), are reported with the following codes:

  • G21.0, Malignant neuroleptic syndrome
  • G21.11, Neuroleptic-induced parkinsonism
  • G21.19, Other drug-induced secondary parkinsonism
  • G21.2, Secondary parkinsonism due to other external agents
  • G21.3, Postencephalitic parkinsonism
  • G21.4, Vascular parkinsonism  
  • G21.8, Other secondary parkinsonism
  • G21.9, Secondary parkinsonism, unspecified

Short Video on Parkinsonism vs. Parkinson’s Disease

A 1-minute video on parkinsonism and Parkinson’s disease


In conclusion, parkinsonism and Parkinson’s disease are not synonymous. A person can have symptoms of Parkinson’s disease without having Parkinson’s. However, if a person is diagnosed with Parkinson’s, it is safe to say he also has parkinsonism.  Likewise, if a person has symptoms of PD and also has other symptoms, chances are he may have Parkinson’s plus syndrome, which may be due to many potential causes. Understanding the distinct aspects of these conditions, along with the pertinent coding guidelines and conventions, will ensure accurate coding for these diagnoses.

Do you want to try your skill with this CPT coding exercise on performing a DaTscan procedure to confirm Parkinson’s disease? Go to the link below to receive FREE access to this coding exercise and many others on our Resources page:

Name That Code! – Coding for DaTscan Procedure (CPT and HCPCS)

Parkinsonism and Parkinson's Disease in ICD-10-CM
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    1. Hi Lidia. Thanks so much for commenting. I’m glad you found the post helpful and hope you checked out the other related posts I provided above.

      Keep on coding!

  1. First of all thank you mam..for giving a detailed explanation on each and every condition…it is very helpful for me…

  2. Hi, Debbie., is there an ICD 10 code for OFF PERIODS of Parkinson’s Disease. A Latorre, MD,

    1. Hi Dr. Latorre,

      Currently, there is not. However, the expansion of code G20 has been proposed, and we may see new codes related to PD and off episodes implemented in October of this year.

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