What is ICD-10 code G31.89?

G31.89 is the ICD-10-CM diagnosis code for Other specified degenerative diseases of nervous system. This code represents other specified degenerative diseases of the nervous system not classified elsewhere, including various progressive neurological conditions affecting the brain and spinal cord. G31.89 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G31.89 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G31.89 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G31.89 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for G31.89?

G31.89 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards G31.89 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting G31.89?

Use this code only when a specific degenerative neurological disease code is not available; always document the specific condition Review documentation carefully to ensure a more specific G31 code is not applicable before assigning this catch-all code

G31.89: Other specified degenerative diseases of nervous system — ICD-10

ICD-10-CM Code View

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Code lookupG31.89Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Other degenerative diseases of the nervous system (G30-G32)

G31.89

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other specified degenerative diseases of nervous system

This code represents other specified degenerative diseases of the nervous system not classified elsewhere, including various progressive neurological conditions affecting the brain and spinal cord.

Buddy Insight

Other specified degenerative diseases of the nervous system captures progressive neurological conditions that have been identified by the provider but do not have their own specific ICD-10 code.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 112

Dementia and Other Specified ...

RAF 0.0

Code Trumping

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Code Book Path

Official

G31Other degenerative diseases of nervous system, not elsewhere classified

G31.8Other specified degenerative diseases of nervous system

G31.89Other specified degenerative diseases of nervous system

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for G31.89 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G31.89 in this effective period.

Related Child Codes

Official

G31.80Leukodystrophy, unspecified

G31.81Alpers disease

G31.82Leigh's disease

G31.83Neurocognitive disorder with Lewy bodies

G31.84Mild cognitive impairment of uncertain or unknown etiology

Includes

Official

ICD-10-CM does not list Includes notes for G31.89 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for G31.89 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G31.89 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G31.89 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G31.89 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation specifying the exact degenerative neurological condition

Clinical evidence supporting the degenerative nature of the disease

Evidence that more specific codes (G31.01-G31.86) have been considered and are not applicable

Neurological examination and/or neuroimaging findings

MEAT Support

HCC Buddy guidance

Documentation specifying the exact degenerative neurological condition

Clinical evidence supporting the degenerative nature of the disease

Evidence that more specific codes (G31.01-G31.86) have been considered and are not applicable

Neurological examination and/or neuroimaging findings

Audit Caution

HCC Buddy guidance

Using G31.89 when a more specific G31.x code exists for the documented condition

Using this code for conditions classified elsewhere in ICD-10 (e.g., metabolic neurological diseases under E-codes)

Not documenting the specific condition name, making it impossible to verify code accuracy on audit

Confusing 'other specified' (G31.89) with 'unspecified' (G31.9) — the former requires a named condition

Common Mistakes

HCC Buddy guidance

G31.9 — Degenerative disease of nervous system, unspecified; use when the specific condition cannot be identified at all

G31.83 — Neurocognitive disorder with Lewy bodies; should be used instead if Lewy body disease is documented

G31.85 — Corticobasal degeneration; has its own specific code

G31.86 — Alexander disease; has its own specific code

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is G31.89 an HCC code?

No. G31.89 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 112, Dementia and Other Specified Brain Disorders

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for G31.89

For G31.89to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G31.89 during that encounter, not just copy-forwarded from a problem list.

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What This Code Means

G31.89 is the ICD-10-CM diagnosis code for other specified degenerative diseases of nervous system. This code represents other specified degenerative diseases of the nervous system not classified elsewhere, including various progressive neurological conditions affecting the brain and spinal cord. G31.89 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering other degenerative diseases of the nervous system (g30-g32).

G31.89 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Does not map to any HCC in V28 or V24 models. Only maps to RxHCC 112 with 0.0 RAF weight. This code has no risk adjustment value in CMS-HCC models. When possible, query the provider for a more specific diagnosis that may carry HCC value.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G31.89 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when a specific degenerative neurological disease code is not available; always document the specific condition
•Review documentation carefully to ensure a more specific G31 code is not applicable before assigning this catch-all code

Clinical Significance

Other specified degenerative diseases of the nervous system captures progressive neurological conditions that have been identified by the provider but do not have their own specific ICD-10 code. This code serves as a catch-all for rare or unusual degenerative conditions while still indicating that a specific diagnosis has been made. It is important for capturing complex neurological comorbidities.

Documentation Requirements

✓Documentation specifying the exact degenerative neurological condition
✓Clinical evidence supporting the degenerative nature of the disease
✓Evidence that more specific codes (G31.01-G31.86) have been considered and are not applicable
✓Neurological examination and/or neuroimaging findings
✓Treatment plan for the specific condition documented

Commonly Confused Codes

•G31.9: Degenerative disease of nervous system, unspecified; use when the specific condition cannot be identified at all
•G31.83: Neurocognitive disorder with Lewy bodies; should be used instead if Lewy body disease is documented
•G31.85: Corticobasal degeneration; has its own specific code
•G31.86: Alexander disease; has its own specific code
•G31.01: Pick's disease; has its own specific code