ICD-10 G04.90
Billable / Specific MCCEncephalitis and encephalomyelitis, unspecified
About ICD-10-CM G04.90
ICD-10-CM code G04.90 represents Encephalitis and encephalomyelitis, unspecified. This is a billable/specific code in the Nervous System chapter (block G04). The 2026 edition of ICD-10-CM G04.90 became effective on October 1, 2025.
Coding Tips for G04.90
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G04.90 is designated MCC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-MCC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag MCC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under G04.90. Per CMS ICD-10-CM Tabular 2026.
- Ventriculitis (cerebral) NOS
Inpatient DRG Impact, MCC
codes Encephalitis and encephalomyelitis, unspecified. As a Major Complication/Comorbidity (MCC), this can shift the DRG assignment to a higher-weighted category, substantial reimbursement impact.
Medicare LCD Coverage for G04.90
Local Coverage Determinations (LCDs) from CMS MACs that list G04.90 as a covered diagnosis.
Showing top 10 of 630 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G04.90.
1 Cigna
5 Medicare
CPT Codes Commonly Billed with G04.90
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
- 95708 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
Convert G04.90 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 |
|---|---|---|
| G04.90 | 3239 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To G04.90
Other codes in section G00-G09 (Inflammatory diseases of the central nervous system).
ICD-10 G04.90, Billing FAQ
Is ICD-10 code G04.90 billable? +
Yes, G04.90 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to G04.90? +
ICD-10 G04.90 includes: Ventriculitis (cerebral) NOS.
Is G04.90 a CC or MCC for inpatient DRG? +
Yes, this code is designated as MCC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with G04.90? +
Procedures frequently paired with G04.90 include: 51741, 51728, 51729, 55899, 51792.
What ICD-9 codes does G04.90 map to? +
Per CMS GEMs, G04.90 maps to ICD-9 codes: 3239. 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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