G04.1
BillableTropical spastic paraplegia
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G04.1 an HCC code?
Yes. G04.1 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 G04.1
For G04.1 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 G04.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G04.1 is the ICD-10-CM diagnosis code for tropical spastic paraplegia. A progressive neurological disorder causing weakness and spasticity in the legs, primarily found in tropical regions and associated with HTLV-1 infection. G04.1 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, G04.1 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, G04.1 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.
Confirm HTLV-1 serology or other diagnostic evidence of tropical spastic paraplegia. Because G04.1 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 G04.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm HTLV-1 serology or other diagnostic evidence of tropical spastic paraplegia
- •Code the underlying HTLV-1 infection separately if documented
Clinical Significance
Tropical spastic paraplegia is a progressive myelopathy associated with HTLV-1 infection that causes significant disability through lower extremity weakness and spasticity. This diagnosis signals a chronic neurological condition requiring ongoing specialist management, rehabilitation services, and monitoring for HTLV-1 associated complications including potential malignancy.
Documentation Requirements
- ✓HTLV-1 serology results or documented positive status
- ✓Progressive lower extremity weakness and spasticity documented on exam
- ✓Neurological examination findings (hyperreflexia, Babinski sign, spastic gait)
- ✓MRI or other imaging of spinal cord if available
- ✓Duration and progression of symptoms
- ✓Current functional status and mobility limitations
Commonly Confused Codes
- •G04.89 — Other myelitis: used when the cause is known but not HTLV-1 related tropical spastic paraplegia
- •G35 — Multiple sclerosis: can present similarly with spastic paraplegia but has different etiology and imaging findings
- •G04.91 — Myelitis, unspecified: should not be used when HTLV-1 associated myelopathy is documented
- •G82.20 — Paraplegia, unspecified: describes the symptom, not the specific disease process