2026 ICD-10-CM Diagnosis Code G04.82Acute flaccid myelitis

ICD-10-CM Codes›G00–G99›G00-G09›G04

ICD-10-CM G04.82
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G04.82 is a billable ICD-10-CM diagnosis code for acute flaccid myelitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis.

Code Identity

ICD-10-CM Code
G04.82
Billable Status
Yes — Valid for Submission
Code Describes
Acute flaccid myelitis
Short Description
Acute flaccid myelitis
Same as the full description in the CMS dataset.
Parent Code
G04.8
Other encephalitis, myelitis and encephalomyelitis

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG00-G09Inflammatory diseases of the central nervous system
CategoryG04Encephalitis, myelitis and encephalomyelitis
This CodeG04.82Acute flaccid myelitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute flaccid myelitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Type 1 Excludes

  • transverse myelitis G37.3

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Myelitis(acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)
      • flaccid

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Acute Flaccid Myelitis

    an acute onset of focal limb weakness that is associated mainly with gray matter abnormalities or csf pleocytosis, but which is without an apparent cause.

Patient EducationClinical

Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is a neurologic disease. It is rare, but serious. It affects an area of the spinal cord called gray matter. This can cause the muscles and reflexes in the body to become weak.

The full article covers:

  • What is acute flaccid myelitis (AFM)?
  • What causes acute flaccid myelitis (AFM)?
  • Who is more likely to develop acute flaccid myelitis (AFM)?
  • What are the symptoms of acute flaccid myelitis (AFM)?
  • How is acute flaccid myelitis (AFM) diagnosed?
  • What are the treatments for acute flaccid myelitis (AFM)?
  • Can acute flaccid myelitis (AFM) be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement G04.82 replaces the following previously assigned code(s):

  • G04.89 - Other myelitis
FY 2022AddedAdded to the ICD-10-CM code setEffective October 1, 2021.
FY 2023–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G04.82Overview

Is G04.82 (Other encephalitis, myelitis and encephalomyelitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report acute flaccid myelitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.