G13.8
BillableSystemic atrophy primarily affecting central nervous system in other diseases classified elsewhere
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G13.8 an HCC code?
No. G13.8 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.
MEAT Criteria for G13.8
For G13.8to 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 G13.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G13.8 is the ICD-10-CM diagnosis code for systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere. Wasting and degeneration of the brain and spinal cord caused by other systemic diseases not specifically listed in other categories. G13.8 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).
G13.8 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.
G13.8 does not map to any V28 or V24 HCC. It maps only to RxHCC 112 (Fibrosis of Lung and Other Chronic Lung Disorders) with 0.0 RAF weight. Minimal direct risk adjustment impact; value depends on the underlying disease code's HCC mapping.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G13.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only after excluding more specific systemic causes
- •Document the underlying disease causing the neurological manifestation
Clinical Significance
Systemic atrophy primarily affecting the central nervous system in other diseases classified elsewhere captures neurodegeneration caused by systemic diseases not specifically listed in other G13 categories. This manifestation code requires dual coding and reflects the neurological complexity added when systemic disease causes brain or spinal cord degeneration.
Documentation Requirements
- ✓Documented central nervous system atrophy or degeneration attributed to a specific systemic disease
- ✓Underlying systemic disease identified and coded as the first-listed diagnosis
- ✓Clinical evidence of neurological decline on examination
- ✓Brain or spinal cord imaging supporting atrophy if available
- ✓Causal relationship between underlying disease and neurological manifestation documented by provider
- ✓Exclusion of other causes of neurodegeneration
Code First
- underlying disease
Commonly Confused Codes
- •G13.0 — Paraneoplastic neuromyopathy: for cancer-related peripheral nerve damage specifically
- •G13.1 — Systemic atrophy in neoplastic disease: for cancer-related central nervous system degeneration
- •G13.2 — Systemic atrophy in myxedema: for hypothyroidism-related neurodegeneration specifically
- •G31.89 — Other specified degenerative diseases of nervous system: for primary neurodegenerative diseases not caused by systemic illness