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ICD-10 Code G04.0: Acute disseminated encephalitis and encephalomyelitis (ADEM)

G04.0 is an ICD-10 diagnosis entry used to group records related to Acute disseminated encephalitis and encephalomyelitis (ADEM). You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

When is it used?

  • May be used when a clinician documents acute disseminated encephalitis and encephalomyelitis (adem) in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
  • This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter
6Diseases of the nervous system (G00-G99)
block
G00-G09Inflammatory diseases of the central nervous system
category
G04Encephalitis, myelitis and encephalomyelitis
currentG04

Official coding notes

Excludes1 (do not code together)
  • acute necrotizing hemorrhagic encephalopathy (G04.3-)
  • other noninfectious acute disseminated encephalomyelitis (noninfectious ADEM) (G04.81)

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

NeurologistGeneral Physician

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.
Legacy codes
G04.0
Replacement codes
G04.00 — Acute disseminated encephalitis and encephalomyelitis, unspecifiedG04.01 — Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)G04.02 — Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis

Common synonyms

Acute disseminated encephalitis and encephalomyelitis (ADEM)Acute disseminated encephalitis and encephalomyelitisAcute disseminated encephalitis and encephalomyelitis ADEM

Frequently asked questions

Code details

CodeG04.0
SystemICD10
Display nameAcute disseminated encephalitis and encephalomyelitis (ADEM)
ChapterDiseases of the nervous system (G00-G99)
BlockInflammatory diseases of the central nervous system

Flags

BillableNo
Valid clinical useNo

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.