G04.82 ICD-10-CM Code: Acute flaccid myelitis
G04.82 maps to CMS-HCC V28 182. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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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
Coefficient HCC 182: 0.478 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 110
Code-level coefficient reference
ESRD/PACE
MappedHCC 72
Code-level coefficient reference
RXHCC
MappedHCC 155
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for G04.82. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99, G04
- certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99, G04
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99, G04
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99, G04
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99, G04
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99, G04
- neoplasms (C00-D49)Inherited from G00-G99, G04
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99, G04
- acute transverse myelitis (G37.3)Inherited from G00-G99, G04
- alcoholic encephalopathy (G31.2)Inherited from G00-G99, G04
- multiple sclerosis (G35-)Inherited from G00-G99, G04
- myalgic encephalomyelitis (G93.32)Inherited from G00-G99, G04
- subacute necrotizing myelitis (G37.4)Inherited from G00-G99, G04
- toxic encephalitis (G92.8)Inherited from G00-G99, G04
- toxic encephalopathy (G92.8)Inherited from G00-G99, G04
Related Codes
Includes
Official- acute ascending myelitisInherited from G04
- meningoencephalitisInherited from G04
- meningomyelitisInherited from G04
Excludes 1
Official- transverse myelitis (G37.3)
- encephalopathy NOS (G93.40)Inherited from G04
Code First
OfficialNo Code First sequencing instructions are included in this display for G04.82. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for G04.82. Check the code and parent instructions in the Code Book.
Code Also
Official- any associated seizure (G40.-, R56.9)Inherited from G04.8
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is G04.82 an HCC code?
Yes. G04.82 (Acute flaccid myelitis) maps to HCC 182, Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.478. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: G04.82 is billable and maps to V28 HCC 182, Spinal Cord Disorders/Injuries. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- G04.82
- Description
- Acute flaccid myelitis
- HCC (V28)
- HCC 182 — Spinal Cord Disorders/Injuries
- RAF reference coefficient
- 0.478
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work G04.82 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for G04.82
For G04.82, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 source-labeled community, non-dual, aged reference coefficient of 0.478. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This code is used for acute presentations; ensure documentation clearly indicates acute onset and flaccid paralysis pattern. For G04.82, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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