G04.89
BillableOther myelitis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G04.89 an HCC code?
Yes. G04.89 maps to Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model (and Spinal Cord Disorders/Injuries under V24).
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 G04.89
For G04.89 to 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 G04.89 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G04.89 is the ICD-10-CM diagnosis code for other myelitis. Inflammation of the spinal cord that doesn't fit into other specific categories, causing pain, weakness, or loss of sensation. G04.89 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering inflammatory diseases of the central nervous system (g00-g09).
Under the CMS-HCC V28 risk adjustment model, G04.89 maps to Spinal Cord Disorders/Injuries (HCC 182) with a community, non-dual, aged base RAF weight of 0.282. Under the older V24 model, G04.89 mapped to the same category but with a base RAF weight of 0.464 — V28 recalibrated weights across the entire model. 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.
Use this code only when the myelitis doesn't meet criteria for other specific G04 codes. Because G04.89 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 G04.89 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 the myelitis doesn't meet criteria for other specific G04 codes
- •Document the underlying cause if known, as this may affect treatment and prognosis
Clinical Significance
Other myelitis represents spinal cord inflammation that does not fit into more specific categories, indicating a significant neurological condition requiring specialist evaluation and management. Accurate capture is essential because myelitis can cause permanent disability and reflects high healthcare resource utilization for diagnostics, treatment, and rehabilitation.
Documentation Requirements
- ✓Clinical findings of spinal cord inflammation (weakness, sensory changes, bowel/bladder dysfunction)
- ✓MRI findings of spinal cord involvement
- ✓Cerebrospinal fluid analysis results
- ✓Underlying etiology if identified (autoimmune, infectious, idiopathic)
- ✓Level of spinal cord involvement (cervical, thoracic, lumbar)
- ✓Documentation that condition does not meet criteria for other specific G04 codes