2026 ICD-10-CM Diagnosis Code G31.85Corticobasal degeneration

ICD-10-CM Codes›G00–G99›G30-G32›G31

ICD-10-CM G31.85
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G31.85 is a billable ICD-10-CM diagnosis code for corticobasal degeneration. 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 Other nervous system disorders (often hereditary or degenerative).

Code Identity

ICD-10-CM Code
G31.85
Billable Status
Yes — Valid for Submission
Code Describes
Corticobasal degeneration
Short Description
Corticobasal degeneration
Same as the full description in the CMS dataset.
Parent Code
G31.8
Other specified degenerative diseases of nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG30-G32Other degenerative diseases of the nervous system
CategoryG31Other degenerative diseases of nervous system, not elsewhere classified
This CodeG31.85Corticobasal degeneration

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Corticobasal degeneration
  • Corticobasal syndrome

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.

    • Degeneration, degenerative
      • corticobasal

Clinical ClassificationClinical

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

CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Corticobasal Degeneration

    rare progressive neurological disorder characterized by parkinsonism, cortical atrophy of multiple areas of the brain including the cerebral cortex and the basal ganglia, cognitive dysfunction and eye movement abnormalities.

Patient EducationClinical

Degenerative Nerve Diseases

Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses.

Read the full article at MedlinePlus

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

Convert G31.85 to ICD-9-CMHistory

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

ICD-9-CM
331.6 Corticobasal degneration
Exact Match The mapping is direct, with no qualifiers.

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 G31.85Overview

Is G31.85 (Other specified degenerative diseases of nervous system) a billable code?

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

What is the ICD-9 equivalent of G31.85?

Under the General Equivalence Mappings, corticobasal degeneration converts to ICD-9-CM 331.6 (corticobasal degneration). The mapping is a direct match.

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.