G13.0
BillableParaneoplastic neuromyopathy and neuropathy
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G13.0 an HCC code?
Yes. G13.0 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome under the V24 model but is not retained in V28.
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 G13.0
For G13.0to 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 G13.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G13.0 is the ICD-10-CM diagnosis code for paraneoplastic neuromyopathy and neuropathy. Nerve and muscle damage that occurs as a complication of cancer, where the immune system attacks nerve tissue in response to the malignancy. G13.0 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 older CMS-HCC V24 model, G13.0 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome (HCC 75) with a community, non-dual, aged base RAF weight of 0.425. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code requires documentation of both the paraneoplastic syndrome and the underlying neoplasm. Because G13.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for G13.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code requires documentation of both the paraneoplastic syndrome and the underlying neoplasm
- •Code the associated malignancy separately using the appropriate neoplasm code
Clinical Significance
Paraneoplastic neuromyopathy and neuropathy represents autoimmune-mediated nerve and muscle damage triggered by an underlying malignancy, often preceding cancer diagnosis. This code is critically important because it signals the need for cancer screening and captures the complexity of managing both the neurological syndrome and the underlying neoplasm.
Documentation Requirements
- ✓Documented paraneoplastic syndrome with neurological involvement
- ✓Underlying malignancy identified and coded separately
- ✓Paraneoplastic antibody testing results (anti-Hu, anti-Yo, anti-CV2, etc.)
- ✓Electromyography and nerve conduction studies documenting the neuropathy/myopathy pattern
- ✓Temporal relationship between neurological symptoms and cancer diagnosis
- ✓Response to cancer treatment if applicable
Commonly Confused Codes
- •G62.9 — Polyneuropathy, unspecified: does not capture the paraneoplastic etiology
- •G73.1 — Lambert-Eaton syndrome in neoplastic disease: specific paraneoplastic neuromuscular junction disorder
- •G63 — Polyneuropathy in diseases classified elsewhere: for neuropathy secondary to non-neoplastic diseases
- •G13.1 — Other systemic atrophy primarily affecting central nervous system in neoplastic disease: for central nervous system involvement rather than peripheral