2026 ICD-10-CM Diagnosis Code G31.1Senile degeneration of brain, not elsewhere classified

ICD-10-CM Codes›G00–G99›G30-G32›G31

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

G31.1 is a billable ICD-10-CM diagnosis code for senile degeneration of brain, not elsewhere classified. 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 Neurocognitive disorders.

Code Identity

ICD-10-CM Code
G31.1
Billable Status
Yes — Valid for Submission
Code Describes
Senile degeneration of brain, not elsewhere classified
Short Description
Senile degeneration of brain, not elsewhere classified
Same as the full description in the CMS dataset.
Parent Code
G31
Other degenerative diseases of nervous system, not elsewhere classified

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 CodeG31.1Senile degeneration of brain, not elsewhere classified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Autonomic nervous system disorder co-occurrent and due to neurodegenerative disorder
  • Cerebellar degeneration
  • Cerebral atrophy
  • Cerebral degeneration
  • Cerebral degeneration presenting primarily with dementia
  • Chorea due to heredodegenerative disorder
  • Degenerative brain disorder
  • Disorder of brain
  • Epilepsy co-occurrent and due to degenerative brain disorder
  • Frontal lobe degeneration
  • Frontotemporal degeneration
  • Lesion of brain
  • Secondary cerebellar degeneration
  • Senile degeneration of brain

Tabular List NotesGuidance

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

Type 1 Excludes

  • Alzheimer's disease G30
  • senility NOS R41.81

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)
      • brain (cortex) (progressive)
        • senile NEC
    • Degeneration, degenerative
      • brain (cortical) (progressive)
        • senile NEC
    • Degeneration, degenerative
      • motor centers, senile
    • Degeneration, degenerative
      • senile
        • brain
    • Degeneration, degenerative
      • senile
        • motor centers
    • Disease, diseased
      • brain
        • senile NEC

Clinical ClassificationClinical

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

CCSR NVS011
Neurocognitive disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • CDR1 Gene|CDR1|CDR1|Cerebellar Degeneration-Related Protein-1 (34kD) Gene

    this gene plays a major role in antigens that are specifically expressed in neuronal cells.

  • CDR1 wt Allele|CDR|CDR Gene|CDR1|CDR34|CDR34 Gene|CDR62A|CDR62A Gene|Cerebellar Degeneration-Related Autoantigen 1 Gene|Cerebellar Degeneration-Related Protein (34kD) Gene|Cerebellar Degeneration-Related Protein-1 (34kD) wt Allele|Cerebellar-Degeneration-Related Antigen 1 Gene

    human cdr1 wild-type allele is located within xq27.1-q27.2 and is approximately 1 kb in length. this allele, which encodes cerebellar degeneration-related antigen 1 protein, is involved in immune reactions and neuronal antigen regulation.

  • Cerebellar Degeneration

    degeneration of the cerebellum. it may be an inherited condition, a paraneoplastic syndrome, or secondary to autoimmune disorders.

  • Cerebellar-Degeneration-Related Antigen 1|CDR|CDR1|CDR1 Protein|CDR34|CDR62A|Cerebellar Degeneration-Related Autoantigen 1|Cerebellar Degeneration-Related Autoantigen, 34-kD|Cerebellar Degeneration-Related Protein (34kD)|Cerebellar Degeneration-Related Protein 1|Cerebellar Degeneration-Related Protein 1, 34kDa|Cerebellar Degeneration-Related Protein-1 (34kD)

    cerebellar degeneration-related antigen 1 (262 aa, ~31 kda) is encoded by the human cdr1 gene. this protein is involved in autoimmune diseases.

  • Paraneoplastic Cerebellar Degeneration

    a rare, immune-mediated disorder characterized by cerebellar degeneration due to the presence of an often undetected malignancy (usually carcinoma or lymphoma) in an anatomic site other than the cerebellum. signs and symptoms include progressive ataxia, dysarthria, and nystagmus.

  • Spinocerebellar Ataxia|Spinocerebellar Degeneration

    an inherited disorder characterized by degeneration of the spinal cord and the cerebellum. symptoms may appear at any age and include progressive loss of coordination of gait, hands, speech, and eye movements.

  • CDR1 Gene|CDR1|CDR1|Cerebellar Degeneration Related 1 Gene

    this gene plays a major role in antigens that are specifically expressed in neuronal cells.

  • CDR1 wt Allele|CDR|CDR34|CDR62A|Cerebellar Degeneration Related 1 wt Allele|Cerebellar Degeneration-Related Autoantigen 1 Gene|Cerebellar Degeneration-Related Autoantigen, 34-kD Gene|Cerebellar Degeneration-Related Protein (34kD) Gene|Cerebellar Degeneration-Related Protein-1 (34kD) Gene|Cerebellar-Degeneration-Related Antigen 1 Gene

    human cdr1 wild-type allele is located within xq27.1-q27.2 and is approximately 1 kb in length. this allele, which encodes cerebellar degeneration-related antigen 1 protein, is involved in immune reactions and neuronal antigen regulation.

  • Cerebellar Degeneration-Related Antigen 1|CDR|CDR1|CDR1 Protein|CDR34|CDR62A|Cerebellar Degeneration-Related Autoantigen 1|Cerebellar Degeneration-Related Autoantigen, 34-kD|Cerebellar Degeneration-Related Protein (34kD)|Cerebellar Degeneration-Related Protein 1, 34kDa|Cerebellar Degeneration-Related Protein-1 (34kD)|Cerebellar-Degeneration-Related Antigen 1

    cerebellar degeneration-related antigen 1 (262 aa, ~31 kda) is encoded by the human cdr1 gene. this protein is involved in autoimmune diseases.

Patient EducationClinical

Dementia

Dementia is a loss of mental functions that is severe enough to affect your daily life and activities. These functions include:

The full article covers:

  • What is dementia?
  • What are the types of dementia?
  • Who is at risk for dementia?
  • What are the symptoms of dementia?
  • How is dementia diagnosed?
  • What are the treatments for dementia?
  • Can dementia be prevented?

Read the full article at MedlinePlus

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

Convert G31.1 to ICD-9-CMHistory

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

ICD-9-CM
331.2 Senile degenerat brain
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 G31.1Overview

Is G31.1 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report senile degeneration of brain, not elsewhere classified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of G31.1?

Under the General Equivalence Mappings, senile degeneration of brain, not elsewhere classified converts to ICD-9-CM 331.2 (senile degenerat brain). 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.