Coding Update: An Index Change for Parkinson’s Disease

It’s hard to believe, but April 1 is right around the corner. As coders, we know that is one of our update dates, and this year we will get new indexing for Parkinson’s disease you should be aware of. 

We will have a new sub-term, Parkinson’s disease – see Disease, Parkinson’s. We will find this added under the main term “Parkinsonism” in the Alphabetic Index. For those of you who code Parkinson’s disease frequently, this will be a welcome change. Currently, the Alphabetic Index entry of Parkinsonism directs us to code G20.C, Parkinsonism, unspecified.

Coders must follow the Excludes 1 note here to find the code for Parkinson’s disease, NOS G20.A1. 

With this addition comes a change to the Alphabetic Index. The main term, Parkinson’s disease, syndrome or tremor – see Parkinsonism – will be deleted and replaced with two new main terms. The new main terms are Parkinson’s disease and Parkinson’s syndrome or tremor. Main-term Parkinson’s disease instructs coders to see Diseases, Parkinson’s. Main term Parkinson’s syndrome or tremor instructs coders to see Parkinsonism. 

All our updates and changes are important, but this one is particularly significant. Going forward, when a coder is assigning for Parkinson’s disease, they will be directed to G20.A1 from the Alphabetic Index.

As I noted before, previously the Index was directing coders to G20.C. The Excludes 1 note would then instruct coders where to find the correct code. 

This isn’t the only change we have had to Parkinson’s disease recently. In 2023, we had an expansion of our codes noting dyskinesia and fluctuations. Codes G20.A1 and G20.A2 are assigned for Parkinson’s disease without dyskinesia, without and with fluctuations, respectively. Remember here that G20.A1 is our Parkinson’s disease NOS option. Codes G20.B1 and G20.B2 are assigned for Parkinson’s disease with dyskinesia, without and with fluctuations, respectively. 

The Coding Clinic edition for the fourth quarter of 2023 did give us some clarification. It defined dyskinesia as the involuntary movement of the face, arms, legs, or the trunk. In its guidance, Coding Clinic noted that while there is no cure for Parkinson’s disease, levodopa is used to relieve the symptoms. Further defining fluctuations in Parkinson’s disease, Coding Clinic referred to “on” and “off” episodes. In an “on” episode, there is a positive response to the levodopa. In “off” episodes, the response to the levodopa wears off and the Parkinson’s symptoms are seen again. In the Tabular List, our Parkinson’s disease codes are identified as with or without mention of those “off” episodes.   

Coding Clinic notes that Parkinson’s disease is a progressive, neurodegenerative disease, again, with no cure at this time. Parkinson’s disease presents with motor symptoms, including tremors of the hands, arms, legs and feet. Other nonmotor symptoms may be present as well. These may include depression, anxiety, or pain. 

There is a “use additional code” note at G20 instructing us to assign an additional code if applicable to identify dementia or mild neurocognitive disorder due to known physiological condition. Our dementia codes include options for with anxiety, behavioral, mood, or psychotic disturbance, or without any behavioral disturbance. 

Be sure to review the April 2026 update for final changes and guidance.