G04.01 ICD-10-CM Code: Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
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)
G04.01
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePostinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
Sudden inflammation of the brain and spinal cord that develops following a recent infection or vaccination.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
MappedHCC 3
Varies by metal level
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 G04.01 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for G04.01 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for G04.01 in this effective period.
Excludes 1
Official- post chickenpox encephalitis (B01.1)
- post measles encephalitis (B05.0)
- post measles myelitis (B05.1)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G04.01 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for G04.01 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for G04.01 in this effective period.
Buddy Documentation Tip
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 →
Is G04.01 an HCC code?
No. G04.01 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
- Code
- G04.01
- Description
- Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
Get the V28 RAF + MEAT cheat sheet
One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.
Free PDF. No card. Unsubscribe anytime.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
G04.01 is the ICD-10-CM diagnosis code for postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious adem). Sudden inflammation of the brain and spinal cord that develops following a recent infection or vaccination. G04.01 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).
G04.01 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Document the preceding infection or vaccination and the time interval between the trigger event and symptom onset.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G04.01 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the preceding infection or vaccination and the time interval between the trigger event and symptom onset
- •Code both the ADEM and the triggering condition when applicable