2026 ICD-10-CM Diagnosis Code G13.8Systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere

ICD-10-CM Codes›G00–G99›G10-G14›G13

ICD-10-CM G13.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G13.8 is a billable ICD-10-CM diagnosis code for systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as myxedema cerebellar degeneration. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (neither hereditary nor degenerative).

Code Identity

ICD-10-CM Code
G13.8
Billable Status
Yes — Valid for Submission
Code Describes
Systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere
Short Description
Systemic atrophy aff cnsl in oth diseases classd elswhr
Parent Code
G13
Systemic atrophies primarily affecting central nervous system in diseases classified elsewhere

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG10-G14Systemic atrophies primarily affecting the central nervous system
CategoryG13Systemic atrophies primarily affecting central nervous system in diseases classified elsewhere
This CodeG13.8Systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere

Code EditsBilling

Medicare Code Editor checks that affect claim validity for G13.8.

Manifestation diagnoses
Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and therefore should not be used as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Myxedema cerebellar degeneration
  • Secondary cerebellar degeneration

Tabular List NotesGuidance

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

Code First

  • underlying disease

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.

    • Atrophy, atrophic(of)
      • systemic affecting central nervous system
        • in
          • specified disease NEC

Clinical ClassificationClinical

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

CCSR NVS020
Other nervous system disorders (neither hereditary nor degenerative)
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Brain Diseases

Your brain is the control center of your body. It controls your thoughts, memory, speech, and movement. It regulates the function of many organs. It's part of your nervous system, which also includes your spinal cord and peripheral nerves. The nervous system sends signals between your brain and the rest of the body.

Read the full article at MedlinePlus

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

Convert G13.8 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
331.7 Cereb degen in oth dis
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G13.8Overview

Is G13.8 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can G13.8 be a principal diagnosis?

No. This is a manifestation code: systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.

What is the ICD-9 equivalent of G13.8?

Under the General Equivalence Mappings, systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere converts to ICD-9-CM 331.7 (cereb degen in oth dis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.