ICD-10 G21.4
Billable / Specific HCC v28: 78Vascular parkinsonism
About ICD-10-CM G21.4
ICD-10-CM code G21.4 represents Vascular parkinsonism. This is a billable/specific code in the Nervous System chapter (block G21). The 2026 edition of ICD-10-CM G21.4 became effective on October 1, 2025.
Coding Tips for G21.4
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G21.4 is a CMS-HCC v28 risk-adjustment code (category 78). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for G21.4
Local Coverage Determinations (LCDs) from CMS MACs that list G21.4 as a covered diagnosis.
Showing top 10 of 320 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G21.4.
2 Cigna
5 Medicare
1 NY Medicaid
CPT Codes Commonly Billed with G21.4
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 51741 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51728 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51729 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 55899 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51792 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51736 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51726 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51727 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51797 CMS LCD: Billing and Coding: Urodynamics CMS LCD
Convert G21.4 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| G21.4 | 3320 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To G21.4
Other codes in section G20-G26 (Extrapyramidal and movement disorders).
ICD-10 G21.4, Billing FAQ
Is ICD-10 code G21.4 billable? +
Yes, G21.4 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
Does G21.4 affect Medicare Advantage HCC risk adjustment? +
Yes. G21.4 maps to CMS-HCC v28 category 78. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with G21.4? +
Procedures frequently paired with G21.4 include: 51741, 51728, 51729, 55899, 51792.
What ICD-9 codes does G21.4 map to? +
Per CMS GEMs, G21.4 maps to ICD-9 codes: 3320. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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