G31.1 ICD-10-CM Code: Senile degeneration of brain, not elsewhere classified
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FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Other degenerative diseases of the nervous system (G30-G32)
G31.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceSenile degeneration of brain, not elsewhere classified
Age-related brain degeneration that does not fit into other specific diagnostic categories; a general classification for senile brain changes.
Buddy Insight
Senile degeneration of brain, not elsewhere classified, captures age-related brain degeneration that does not fit into specific diagnostic categories like Alzheimer's or frontotemporal dementia.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
MappedHCC 112
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for G31.1 in this effective period.
Excludes 2
Official- Reye's syndrome (G93.7)
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for G31.1 in this effective period.
Excludes 1
Official- Alzheimer's disease (G30.-)
- senility NOS (R41.81)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G31.1 in this effective period.
Use Additional
Official- code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify:
- dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4)
- dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)
- dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)
- dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)
Code Also
OfficialICD-10-CM does not list Code Also instructions for G31.1 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 G31.1 an HCC code?
No. G31.1 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
HCC Category Mapping
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.
Work G31.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for G31.1
For G31.1to 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 G31.1 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
G31.1 is the ICD-10-CM diagnosis code for senile degeneration of brain, not elsewhere classified. Age-related brain degeneration that does not fit into other specific diagnostic categories; a general classification for senile brain changes. G31.1 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).
G31.1 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 the CMS-HCC models, making it important to query providers for more specific diagnoses that may have HCC value (such as Alzheimer's disease or other specified dementias).
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G31.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should only be used when the specific cause of brain degeneration cannot be identified or classified elsewhere
- •Avoid using this code if a more specific diagnosis (like Alzheimer's or Lewy body disease) is documented
Clinical Significance
Senile degeneration of brain, not elsewhere classified, captures age-related brain degeneration that does not fit into specific diagnostic categories like Alzheimer's or frontotemporal dementia. This code represents a documentation improvement opportunity, as more specific diagnoses are preferred when clinical evidence supports them. These patients still require cognitive monitoring and support services.
Documentation Requirements
- ✓Documentation of age-related brain degeneration confirmed by clinical assessment
- ✓Evidence that more specific diagnoses (Alzheimer's, Lewy body, frontotemporal) have been considered and excluded
- ✓Cognitive testing showing decline from baseline
- ✓Neuroimaging findings showing non-specific cerebral atrophy
- ✓Functional status assessment documenting impact on daily living
Commonly Confused Codes
- •G30.1: Alzheimer's disease with late onset; use when Alzheimer's pathology is confirmed
- •G30.9: Alzheimer's disease, unspecified; use when Alzheimer's is specifically diagnosed
- •R41.81: Age-related cognitive decline; use for normal aging-related cognitive changes without pathology
- •G31.9: Degenerative disease of nervous system, unspecified; broader category including non-brain degeneration
- •F03.90: Unspecified dementia without behavioral disturbance; use when dementia criteria are met