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G04.81 ICD-10-CM Code: Other encephalitis and encephalomyelitis

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
4 inclusion terms · 1 Excludes1 · 7 Excludes2 · 1 code-also instruction

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 023 — CRANIOTOMY WITH MAJOR DEVICE IMPLANT OR ACUTE COMPLEX CNS PRINCIPAL DIAGNOSIS WITH MCC OR ANTINEOPLASTIC IMPLANT OR EPILEPSY WITH NEUROSTIMULATOR (MDC 01)
  • MS-DRG 024 — CRANIOTOMY WITH MAJOR DEVICE IMPLANT OR ACUTE COMPLEX CNS PRINCIPAL DIAGNOSIS WITHOUT MCC (MDC 01)
  • MS-DRG 097 — NON-BACTERIAL INFECTION OF NERVOUS SYSTEM EXCEPT VIRAL MENINGITIS WITH MCC (MDC 01)
  • MS-DRG 098 — NON-BACTERIAL INFECTION OF NERVOUS SYSTEM EXCEPT VIRAL MENINGITIS WITH CC (MDC 01)
  • MS-DRG 099 — NON-BACTERIAL INFECTION OF NERVOUS SYSTEM EXCEPT VIRAL MENINGITIS WITHOUT CC/MCC (MDC 01)
  • MS-DRG 974 — HIV WITH MAJOR RELATED CONDITION WITH MCC (MDC 25)
  • MS-DRG 975 — HIV WITH MAJOR RELATED CONDITION WITH CC (MDC 25)
  • MS-DRG 976 — HIV WITH MAJOR RELATED CONDITION WITHOUT CC/MCC (MDC 25)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for G04.81 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on G04.81 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • acute ascending myelitis
  • meningoencephalitis
  • meningomyelitis

Source: inherited from G04

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Noninfectious acute disseminated encephalomyelitis (noninfectious ADEM)

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from G04

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from G04

Code Also

Additional codes that may be required to fully describe the encounter.

Source: inherited from G04.8

Coder workflow for G04.81

MedCoder structured workflow — derived from this code’s own official record

Before you code G04.81

  1. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on G04.81; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

    ReviewG04.82

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with G04.81. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in G04.81’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewG93.40

Consider G04.81. Then review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes1 — check before selecting G04.81(1 note)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with G04.81: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareG93.40

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of G04.81(7 notes)

    Coding workflow: The conditions named in this note are not included in G04.81. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareG37.3, G31.2, G35, G93.32, G37.4, G92.8

    See the official tabular notes · Guidelines I.A.12.b

  • Code Also — related condition(1 note)

    Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

    ReviewG40, R56.9

    See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition G04.81 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewG93.40

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Other encephalitis and encephalomyelitis is a billable ICD-10-CM diagnosis code (G04.81).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (10)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. 1 Code Also note — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
  2. 1 Excludes1 entry — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
  3. 7 Excludes2 entries — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • MCC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name G04.81 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes1 notes: G03 — Meningitis due to other and unspecified causes (via G04.-), G04.0 — Acute disseminated encephalitis and encephalomyelitis (ADEM).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Excludes2 note: G95 — Other and unspecified diseases of spinal cord (via G04.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 1 Code Also instruction: G37.81 — Myelin oligodendrocyte glycoprotein antibody disease.

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: MCC — Major Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 181 clinically related codes on its CMS exclusion list. Does not count toward severity when the stay groups to DRGs 974-976 (HIV with Major Related Condition).

Named in the grouper logic of 8 MS-DRGs: DRG 023 (MDC 01), DRG 024 (MDC 01), DRG 097 (MDC 01), DRG 098 (MDC 01), DRG 099 (MDC 01), DRG 974 (MDC 25), DRG 975 (MDC 25), DRG 976 (MDC 25).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):NVS002 — Encephalitis (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as MCC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

G00.9 — Bacterial meningitis, unspecified, G03.0 — Nonpyogenic meningitis, G03.1 — Chronic meningitis, G03.2 — Benign recurrent meningitis [Mollaret], G03.8 — Meningitis due to other specified causes, G03.9 — Meningitis, unspecified, G04.00 — Acute disseminated encephalitis and encephalomyelitis, unspecified, G04.01 — Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM), G04.2 — Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified, G04.31 — Postinfectious acute necrotizing hemorrhagic encephalopathy, G04.89 — Other myelitis, G04.90 — Encephalitis and encephalomyelitis, unspecified, G04.91 — Myelitis, unspecified, G37.0 — Diffuse sclerosis of central nervous system, G37.4 — Subacute necrotizing myelitis of central nervous system, G37.5 — Concentric sclerosis [Balo] of central nervous system, G61.0 — Guillain-Barre syndrome, G96.9 — Disorder of central nervous system, unspecified, G98.0 — Neurogenic arthritis, not elsewhere classified, G98.8 — Other disorders of nervous system, +160 more

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Encephalitis).

B10.09 — Other human herpesvirus encephalitis, B26.2 — Mumps encephalitis, B40.81 — Blastomycotic meningoencephalitis, B57.42 — Meningoencephalitis in Chagas' disease, B58.2 — Toxoplasma meningoencephalitis, B60.11 — Meningoencephalitis due to Acanthamoeba (culbertsoni), G04.00 — Acute disseminated encephalitis and encephalomyelitis, unspecified, G04.01 — Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM), G04.02 — Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis, G04.2 — Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified, G04.30 — Acute necrotizing hemorrhagic encephalopathy, unspecified, G04.31 — Postinfectious acute necrotizing hemorrhagic encephalopathy, G04.32 — Postimmunization acute necrotizing hemorrhagic encephalopathy, G04.39 — Other acute necrotizing hemorrhagic encephalopathy, G04.82 — Acute flaccid myelitis, G04.89 — Other myelitis, G04.90 — Encephalitis and encephalomyelitis, unspecified, G04.91 — Myelitis, unspecified, G05.3 — Encephalitis and encephalomyelitis in diseases classified elsewhere, G05.4 — Myelitis in diseases classified elsewhere, +35 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Encephalomyelitis”, “Leukoencephalitis”, “Encephalitis”, …; these codes share that main term but sit in a different category of the Tabular List.

B45.1 — Cerebral cryptococcosis (Torula, torular), B56.9 — African trypanosomiasis, unspecified (in, African trypanosomiasis), B57.42 — Meningoencephalitis in Chagas' disease (in, Chagas' disease), B58.2 — Toxoplasma meningoencephalitis (in, toxoplasmosis), B60.2 — Naegleriasis (in, naegleriasis), B71.9 — Cestode infection, unspecified (parasitic NOS), B75 — Trichinellosis (trichinosis), B83.2 — Angiostrongyliasis due to Parastrongylus cantonensis (eosinophilic), B89 — Unspecified parasitic disease (parasitic NEC), B99 — Other and unspecified infectious diseases (in, infectious disease NEC), G00.0 — Hemophilus meningitis (influenzal), G05.3 — Encephalitis and encephalomyelitis in diseases classified elsewhere (in diseases classified elsewhere), G36.1 — Acute and subacute hemorrhagic leukoencephalitis [Hurst] (acutehemorrhagic), G37.0 — Diffuse sclerosis of central nervous system (periaxial), G37.5 — Concentric sclerosis [Balo] of central nervous system (periaxialis), G92.8 — Other toxic encephalopathy (toxic NEC), G93.32 — Myalgic encephalomyelitis/chronic fatigue syndrome (myalgic), H66.40 — Suppurative otitis media, unspecified, unspecified ear (otitic NEC), M32.19 — Other organ or system involvement in systemic lupus erythematosus (lupus erythematosus, systemic), P37.1 — Congenital toxoplasmosis (in, toxoplasmosis, congenital), +42 more

Contextual Map

Every relationship of G04.81 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run G04.81 with these 4 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Excludes2 notes

Referenced by Code Also instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 8,892 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
  • MDC 25 — Human Immunodeficiency Virus Infections[MDC crossing]: “Human Immunodeficiency Virus Infections — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (10)

  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute), acute, disseminated, noninfectious[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute), Rasmussen[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute), specified NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute), suppurative[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Encephalomyelitis, acute disseminated, noninfectious[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Encephalomyelitis, specified NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Leukoencephalitis[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Meningoencephalitis, specified organism NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • and 2 more

Nearest codes (18)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "G04.81 — Other encephalitis and encephalomyelitis." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/g04.81-other-encephalitis-and-encephalomyelitis

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Other encephalitis and encephalomyelitis

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to G04.81 in its code family, with their registry titles.

View all codes in the G04 family