G04 ICD-10-CM Code: Encephalitis, myelitis and encephalomyelitis
G04 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC coding software
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Inflammatory diseases of the central nervous system (G00-G09)
G04
Header CodeICD-10-CMOfficial ICD-10-CMCodebook guidanceEncephalitis, myelitis and encephalomyelitis
Encephalitis, myelitis and encephalomyelitis
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for G04 in this effective period.
Excludes 2
Official- acute transverse myelitis (G37.3)
- alcoholic encephalopathy (G31.2)
- multiple sclerosis (G35-)
- myalgic encephalomyelitis (G93.32)
- subacute necrotizing myelitis (G37.4)
Related Child Codes
Includes
Official- acute ascending myelitis
- meningoencephalitis
- meningomyelitis
Excludes 1
Official- encephalopathy NOS (G93.40)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G04 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for G04 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for G04 in this effective period.
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
- Code
- G04
- Description
- Encephalitis, myelitis and encephalomyelitis
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- No
- Payment year
- 2026
Coder workflow notes
Get the V28 mapping + MEAT cheat sheet
One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.
Free PDF. No card. Unsubscribe anytime.
What This Code Means
G04 is the ICD-10-CM diagnosis code for encephalitis, myelitis and encephalomyelitis. G04 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering inflammatory diseases of the central nervous system (g00-g09).
Header codes like G04 cannot be reported on claims directly; they organize child codes that share clinical context. Coders should select the billable child code that matches the documented presentation and then verify its current source-backed HCC mapping. Do not infer a child code or risk adjustment value from the header alone.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for G04 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Includes
- acute ascending myelitis
- meningoencephalitis
- meningomyelitis
Excludes 1, Do NOT code together
- encephalopathy NOS (G93.40)