G11.2 maps to CMS-HCC V28 200. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupG11.2

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Systemic atrophies primarily affecting the central nervous system (G10-G14)

G11.2

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

Late-onset cerebellar ataxia

Late-onset cerebellar ataxia is a disorder affecting balance and coordination that develops in adulthood or later in life.

Buddy Insight

Late-onset cerebellar ataxia encompasses progressive coordination disorders that develop in adulthood, including many spinocerebellar ataxias.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 200

Friedreich and Other Heredita...

Coefficient HCC 200: 0.279 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Context needed

HCC 119

Conditional HHS-HCC mapping: HCC 119 when age >=15. Select the member context before showing a coefficient reference. Metal level and model segment are required for coefficients; no single RAF is shown.

Coefficient needs member context

ESRD/PACE

Context needed

HCC 72

ESRD candidates: HCC 72 when age >= 15. ESRD mapping is separate from PACE. Dialysis, graft, age, and other member context determine the applicable coefficient.

Coefficient needs member context

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

G11Hereditary ataxia G11.2Late-onset cerebellar ataxia

Inclusion Terms

Official

No inclusion terms are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Excludes 2

Official

certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99, G11
certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99, G11
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99, G11
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99, G11
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99, G11
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99, G11
neoplasms (C00-D49)Inherited from G00-G99, G11
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99, G11
cerebral palsy (G80.-)Inherited from G00-G99, G11
hereditary and idiopathic neuropathy (G60.-)Inherited from G00-G99, G11
metabolic disorders (E70-E88)Inherited from G00-G99, G11

Related Codes

Official

G11.0Congenital nonprogressive ataxia G11.1Early-onset cerebellar ataxia G11.3Cerebellar ataxia with defective DNA repair G11.4Hereditary spastic paraplegia G11.5Hypomyelination - hypogonadotropic hypogonadism - hypodontia

Includes

Official

No Includes notes are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for G11.2. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Age of onset documented as adulthood or later life

Progressive nature of cerebellar symptoms documented

Neurological examination findings (gait ataxia, limb dysmetria, dysarthria, nystagmus)

Brain MRI showing cerebellar atrophy if performed

MEAT Support

HCC Buddy guidance

Age of onset documented as adulthood or later life

Progressive nature of cerebellar symptoms documented

Neurological examination findings (gait ataxia, limb dysmetria, dysarthria, nystagmus)

Brain MRI showing cerebellar atrophy if performed

Audit Caution

HCC Buddy guidance

Using symptom code R27.0 (ataxia, unspecified) instead of the definitive diagnosis code when late-onset cerebellar ataxia has been diagnosed

Not distinguishing between early-onset and late-onset based on documented age of symptom onset

Failing to document the specific spinocerebellar ataxia type when genetic testing has been performed

Confusing alcoholic cerebellar degeneration (G31.2) with idiopathic late-onset cerebellar ataxia

Common Mistakes

HCC Buddy guidance

G11.10 — Early-onset cerebellar ataxia: onset in childhood, not adulthood

R27.0 — Ataxia, unspecified: a symptom code, not appropriate when a specific ataxia diagnosis is established

G31.89 — Other specified degenerative diseases of nervous system: broader category that may overlap

G11.9 — Hereditary ataxia, unspecified: use only when the hereditary nature is confirmed but onset timing is unknown

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is G11.2 an HCC code?

Yes. G11.2 (Late-onset cerebellar ataxia) maps to HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.279. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: G11.2 is billable and maps to V28 HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: G11.2
Description: Late-onset cerebellar ataxia
HCC (V28): HCC 200 — Friedreich and Other Hereditary Ataxias; Huntington Disease
RAF reference coefficient: 0.279
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease

0.279

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work G11.2 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G11.2

For G11.2, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

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What This Code Means

G11.2 is the ICD-10-CM diagnosis code for late-onset cerebellar ataxia. Late-onset cerebellar ataxia is a disorder affecting balance and coordination that develops in adulthood or later in life. G11.2 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering systemic atrophies primarily affecting the central nervous system (g10-g14).

Under the CMS-HCC V28 risk adjustment model, G11.2 maps to Friedreich and Other Hereditary Ataxias; Huntington Disease (HCC 200) with a source-labeled community, non-dual, aged reference coefficient of 0.279. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Document the age of onset to confirm it qualifies as late-onset. For G11.2, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for G11.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the age of onset to confirm it qualifies as late-onset
•Specify the type if known (e.g., spinocerebellar ataxia, multiple system atrophy) for more precise coding

Clinical Significance

Late-onset cerebellar ataxia encompasses progressive coordination disorders that develop in adulthood, including many spinocerebellar ataxias. These conditions cause significant disability through progressive gait instability, falls, dysarthria, and eventual loss of independence, requiring long-term neurological management and rehabilitation.

Documentation Requirements

✓Age of onset documented as adulthood or later life
✓Progressive nature of cerebellar symptoms documented
✓Neurological examination findings (gait ataxia, limb dysmetria, dysarthria, nystagmus)
✓Brain MRI showing cerebellar atrophy if performed
✓Genetic testing results for spinocerebellar ataxia subtypes if obtained
✓Family history assessment for hereditary vs sporadic forms

Commonly Confused Codes

•G11.10: Early-onset cerebellar ataxia: onset in childhood, not adulthood
•R27.0: Ataxia, unspecified: a symptom code, not appropriate when a specific ataxia diagnosis is established
•G31.89: Other specified degenerative diseases of nervous system: broader category that may overlap
•G11.9: Hereditary ataxia, unspecified: use only when the hereditary nature is confirmed but onset timing is unknown