G04.82 ICD-10-CM Code: Acute flaccid myelitis
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Inflammatory diseases of the central nervous system (G00-G09)
G04.82
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceAcute flaccid myelitis
A sudden onset condition causing weakness and paralysis in the spinal cord, often affecting the arms and legs with a flaccid (floppy) quality.
Buddy Insight
Acute flaccid myelitis is a serious neurological emergency characterized by sudden-onset limb weakness with flaccid paralysis, often affecting children.
CMS-HCC V28
MappedHCC 182
RAF 0.282
CMS-HCC V24
MappedHCC 72
RAF 0.464
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 72
RAF 0.0
RXHCC
MappedHCC 155
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for G04.82 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for G04.82 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for G04.82 in this effective period.
Excludes 1
Official- transverse myelitis (G37.3)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G04.82 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for G04.82 in this effective period.
Code Also
Official- any associated seizure (G40.-, R56.9)
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is G04.82 an HCC code?
Yes. G04.82 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 G04.82
For G04.82to 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 G04.82 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
G04.82 is the ICD-10-CM diagnosis code for acute flaccid myelitis. A sudden onset condition causing weakness and paralysis in the spinal cord, often affecting the arms and legs with a flaccid (floppy) quality. G04.82 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, G04.82 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, G04.82 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.
This code is used for acute presentations; ensure documentation clearly indicates acute onset and flaccid paralysis pattern. Because G04.82 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 G04.82 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code is used for acute presentations; ensure documentation clearly indicates acute onset and flaccid paralysis pattern
- •Look for associated viral infections or recent vaccinations in the medical record, as these are common triggers
Clinical Significance
Acute flaccid myelitis is a serious neurological emergency characterized by sudden-onset limb weakness with flaccid paralysis, often affecting children. It is a reportable condition to the Centers for Disease Control and Prevention and typically follows viral illness, requiring intensive acute care and long-term rehabilitation services.
Documentation Requirements
- ✓Acute onset of flaccid limb weakness documented with timeline
- ✓MRI findings showing spinal cord lesions (gray matter involvement)
- ✓Cerebrospinal fluid analysis results
- ✓Recent viral illness or vaccination history
- ✓Neurological examination documenting flaccid (not spastic) weakness pattern
- ✓Electromyography or nerve conduction study results if performed
Excludes 1, Do NOT code together
- transverse myelitis (G37.3)
Commonly Confused Codes
- •G04.89 — Other myelitis: used for non-flaccid myelitis presentations or when flaccid pattern is not documented
- •G61.0 — Guillain-Barre syndrome: presents with ascending flaccid paralysis but involves peripheral nerves, not spinal cord gray matter
- •G04.91 — Myelitis, unspecified: should not be used when acute flaccid myelitis is clearly documented
- •A80.39 — Acute paralytic poliomyelitis: similar presentation but caused by poliovirus