G37.4
BillableSubacute necrotizing myelitis of central nervous system
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G37.4 an HCC code?
Yes. G37.4 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 G37.4
For G37.4 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 G37.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G37.4 is the ICD-10-CM diagnosis code for subacute necrotizing myelitis of central nervous system. A subacute condition where the spinal cord develops areas of tissue death and inflammation due to demyelination, causing progressive neurological deterioration. G37.4 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering demyelinating diseases of the central nervous system (g35-g37).
Under the CMS-HCC V28 risk adjustment model, G37.4 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, G37.4 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.
Distinguish 'subacute' onset (days to weeks) from acute presentation; document timeline carefully. Because G37.4 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 G37.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Distinguish 'subacute' onset (days to weeks) from acute presentation; document timeline carefully
- •Confirm necrotizing features on imaging and rule out infectious or vascular causes
Clinical Significance
Subacute necrotizing myelitis of the central nervous system represents a progressive condition where spinal cord tissue undergoes necrosis (death) and inflammation over a subacute timeframe. It is more insidious than acute transverse myelitis and carries a worse prognosis due to the tissue destruction. Accurate coding reflects the severity and progressive nature of this serious spinal cord condition.
Documentation Requirements
- ✓Documentation specifying subacute necrotizing myelitis
- ✓MRI showing spinal cord lesions with evidence of necrosis
- ✓Documentation of the subacute timeline (days to weeks of progressive symptoms)
- ✓Evidence distinguishing from acute transverse myelitis (G37.3) by timeline and necrotizing features
- ✓Neurological examination documenting progressive motor, sensory, and autonomic deficits
- ✓Workup ruling out infectious, vascular, and compressive etiologies
- ✓Treatment plan and prognosis discussion
Commonly Confused Codes
- •G37.3 — Acute transverse myelitis in demyelinating disease; acute onset without necrotizing features
- •G04.91 — Myelitis, unspecified; does not capture the necrotizing or subacute nature
- •G95.19 — Other vascular myelopathies; vascular etiology rather than demyelinating/necrotizing
- •G95.89 — Other specified diseases of spinal cord; too nonspecific
- •G36.0 — Neuromyelitis optica; can cause necrotizing myelitis but is a specific disease entity