DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

G04 Encephalitis, myelitis and encephalomyelitis

  • Header · not billable

G04 is not billable. The category heads 14 billable codes in FY2027, grouped under 6 subdivisions.

Index → code

Where it sits

  1. Chapter 6 Diseases of the nervous system (G00-G99)
  2. G00-G09 Inflammatory diseases of the central nervous system (G00-G09)
  3. G04 Encephalitis, myelitis and encephalomyelitis
Billable codes
14
Subdivisions
6
CC / MCC codes
1 / 13
HCC V28 codes
4
New FY2027
0
Index entries
70

Codes in G04

  1. G04.0
    Acute disseminated encephalitis and encephalomyelitis (ADEM)
    Header
    Excludes1 2

    Excludes1

    • acute necrotizing hemorrhagic encephalopathy (G04.3-) G04.3
    • other noninfectious acute disseminated encephalomyelitis (noninfectious ADEM) (G04.81) G04.81
  2. G04.00
    Acute disseminated encephalitis and encephalomyelitis, unspecified
    BillableMCC
  3. G04.01
    Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
    BillableMCC
    Excludes1 3

    Excludes1

    • post chickenpox encephalitis (B01.1) B01.1
    • post measles encephalitis (B05.0) B05.0
    • post measles myelitis (B05.1) B05.1
  4. G04.02
    Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis
    BillableMCC
    Inclusion terms 2, Use additional code 1

    Inclusion terms

    • Encephalitis, post immunization
    • Encephalomyelitis, post immunization

    Use additional code

  5. G04.1
    Tropical spastic paraplegia
    BillableCC182
  6. G04.2
    Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified
    BillableMCC
  7. G04.3
    Acute necrotizing hemorrhagic encephalopathy
    Header
    Excludes1 1

    Excludes1

    • acute disseminated encephalitis and encephalomyelitis (G04.0-) G04.0
  8. G04.30
    Acute necrotizing hemorrhagic encephalopathy, unspecified
    BillableMCC
  9. G04.31
    Postinfectious acute necrotizing hemorrhagic encephalopathy
    BillableMCC
  10. G04.32
    Postimmunization acute necrotizing hemorrhagic encephalopathy
    BillableMCC
    Use additional code 1

    Use additional code

  11. G04.39
    Other acute necrotizing hemorrhagic encephalopathy
    BillableMCC
    Code also 1

    Code also

    • underlying etiology, if applicable
  12. G04.8
    Other encephalitis, myelitis and encephalomyelitis
    Header
    Code also 1

    Code also

    • any associated seizure (G40.-, R56.9) G40 R56.9
  13. G04.81
    Other encephalitis and encephalomyelitis
    BillableMCC
    Inclusion terms 1

    Inclusion terms

    • Noninfectious acute disseminated encephalomyelitis (noninfectious ADEM)
  14. G04.82
    Acute flaccid myelitis
    BillableMCC182
    Excludes1 1

    Excludes1

    • transverse myelitis (G37.3) G37.3
  15. G04.89
    Other myelitis
    BillableMCC182
  16. G04.9
    Encephalitis, myelitis and encephalomyelitis, unspecified
    Header
  17. G04.90
    Encephalitis and encephalomyelitis, unspecified
    BillableMCC
    Inclusion terms 1

    Inclusion terms

    • Ventriculitis (cerebral) NOS
  18. G04.91
    Myelitis, unspecified
    BillableMCC182

CC/MCC: as a secondary diagnosis, unless the principal diagnosis is on the code’s PDX exclusion list (MS-DRG v44 Appendix C; list on the code card).

Sources of each column.

Instructions

At G04

Includes

  • acute ascending myelitis
  • meningoencephalitis
  • meningomyelitis

Excludes1

  • encephalopathy NOS (G93.40) G93.40

Excludes2

  • acute transverse myelitis (G37.3) G37.3
  • alcoholic encephalopathy (G31.2) G31.2
  • multiple sclerosis (G35-) G35
  • myalgic encephalomyelitis (G93.32) G93.32
  • subacute necrotizing myelitis (G37.4) G37.4
  • toxic encephalitis (G92.8) G92.8
  • toxic encephalopathy (G92.8) G92.8

Notes that also apply

Chapter 6 instructions (Excludes2 8): printed on the chapter 6 page.

Index entries

  • Leukoencephalitis → G04.81
  • Rasmussen encephalitis → G04.81
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) → G04.90
  • Encephalomyelitis → G04.90
  • Hematomyelitis → G04.90
  • Meningoencephalitis → G04.90
  • Ventriculitis (cerebral) → G04.90
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute) → G04.91
  • Myeloradiculitis → G04.91
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)disseminated, acute → G04.00
  • Encephalomyelitisacute disseminated → G04.00
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)postinfectious NEC → G04.01
  • Encephalomyelitispostinfectious NEC → G04.01
  • Leukoencephalitispostinfectious → G04.01
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)following vaccination or other immunization procedure → G04.02
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)postimmunization → G04.02
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)postvaccinal → G04.02
  • Encephalomyelitispostvaccinal → G04.02
  • Leukoencephalopathypostimmunization and postvaccinal → G04.02
  • Meningoencephalomyelitispostimmunization or postvaccination → G04.02
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)postimmunization → G04.02
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)postvaccinal → G04.02
  • Paraplegia (lower)tropical spastic → G04.1
  • Meningoencephalitisbacterial NEC → G04.2
  • Meningoencephalitispneumococcal → G04.2
  • Meningoencephalitisstaphylococcal → G04.2
  • Meningoencephalitisstreptococcal → G04.2
  • Meningomyelitisbacterial NEC → G04.2
  • Encephalomyelitisacute necrotizing hemorrhagic → G04.30
  • Encephalopathy (acute)acute necrotizing hemorrhagic → G04.30
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Rasmussen → G04.81
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)specified NEC → G04.81
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)suppurative → G04.81
  • Encephalomyelitisspecified NEC → G04.81
  • Meningoencephalitisspecified organism NEC → G04.81
  • SyndromeRasmussen → G04.81
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)flaccid → G04.82
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)postinfectious NEC → G04.89
  • Myelitis (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)specified NEC → G04.89
  • Infection, infected, infective (opportunistic)brain → G04.90

30 more, longer entries are not listed; the search box finds them by word.

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