Crystal's Coder Hub🧬 ICD-10-CM G37.3 — Acute Transverse Myelitis In Demyelinating Disease Of Central Nervous System
Billable Code Confirmed
ICD-10-CM G37.3 is a valid, billable 4-character diagnosis code. The first three characters (G37) specify other demyelinating diseases of the central nervous system, and the 4th character (3) specifies the acute transverse myelitis variant. No additional characters are required.
Non-Billable Parent Codes — Never Submit These
- ❌
G37— 3-character header — Lacks specificity regarding the exact type of demyelinating disease.Always submit G37.3 (all 4 characters) when acute transverse myelitis or idiopathic transverse myelopathy is documented.
Clinical Context: Specificity of the Underlying Condition
ICD-10-CM G37.3 is used when transverse myelitis occurs in the context of an unspecified demyelinating disorder, or when it is diagnosed as “idiopathic” (NOS). However, transverse myelitis is frequently the first manifestation of Multiple Sclerosis (MS) or Neuromyelitis Optica (NMO). If the patient is known to have MS or NMO, G37.3 cannot be used due to explicit Excludes1 guidelines.
Code Classification
ICD-10-CM Diagnosis Code — wRVU, assistant payable, and global period fields are not applicable. See CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections for associated procedural billing.
🔍 Code Description
ICD-10-CM G37.3 classifies Acute transverse myelitis in demyelinating disease of central nervous system.
Pathophysiologically, transverse myelitis involves focal inflammation across both sides of one level, or segment, of the spinal cord. This inflammatory process damages or destroys the myelin sheath surrounding the nerve fibers, disrupting communications between the nerves in the spinal cord and the rest of the body.
Clinically, patients present with rapid onset (over hours to days) of motor weakness (often progressing to paraparesis or paraplegia), sensory alterations (numbness, tingling, or a distinct “sensory band” around the torso), and autonomic dysfunction (urinary retention or bowel incontinence). MRI of the spine characteristically shows a focal hyperintense demyelinating lesion, and cerebrospinal fluid (CSF) analysis often reveals pleocytosis.
🌳 Code Tree / Hierarchyvgv
G37 Other demyelinating diseases of central nervous system ❌ Non-billable
│
├── G37.0 Diffuse sclerosis of central nervous system ✅ Billable
├── G37.1 Central demyelination of corpus callosum ✅ Billable
├── G37.2 Central pontine myelinolysis ✅ Billable
├── G37.3 Acute transverse myelitis in demyelinating disease... ◀ THIS CODE ✅ Billable
├── G37.4 Subacute necrotizing myelitis of central nervous system ✅ Billable
├── G37.5 Concentric sclerosis [Balo] of central nervous system ✅ Billable
├── G37.8- Other specified demyelinating diseases of central nervous system
└── G37.9 Demyelinating disease of central nervous system, unspecified ✅ Billable
✅ Includes
The following clinical terms and diagnoses map directly to G37.3 when documented in the medical record:
- Acute transverse myelitis NOS
- Acute transverse myelopathy
- Idiopathic acute transverse myelitis
- Transverse myelitis associated with unspecified central nervous system demyelination
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with CODE
| Code | Description | Note |
|---|---|---|
| G35.- | Multiple sclerosis | Mutually exclusive. If the transverse myelitis is explicitly documented as a manifestation of a patient’s multiple sclerosis, use the appropriate MS code instead. |
| G36.0 | Neuromyelitis optica [Devic’s disease] | Mutually exclusive. NMO frequently presents with longitudinally extensive transverse myelitis (LETM). If NMO is the confirmed diagnosis, code G36.0 exclusively. |
| G04.82 | Acute flaccid myelitis | Clinically distinct syndrome (often post-viral) predominantly affecting the gray matter (anterior horn cells) rather than a demyelinating white matter disease. |
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| G04.- | encephalitis, myelitis and encephalomyelitis | General infectious or inflammatory myelitis codes (e.g., viral myelitis) are distinct from the primary demyelinating condition described by G37.3. |
📋 Clinical Overview
Associated Manifestations (Code Also)
Transverse myelitis rarely exists without severe functional deficits. Coders should review the documentation and capture the resulting impairments to accurately reflect patient complexity:
- G82.20 — Paraplegia, unspecified
- R32 — Unspecified urinary incontinence
- R33.9 — Retention of urine, unspecified
- R20.2 — Paresthesia of skin
Residual Deficits vs. Acute Phase
If a patient is seen in an outpatient clinic years after the acute transverse myelitis event and still has paraplegia, code G37.3 as the chronic etiology alongside the paraplegia code. It remains the underlying definitive diagnosis for the permanent deficit.
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024-2025 Implementation) |
| HCC Assignment | ✅ Mapped — HCC 72 |
| HCC Category | Spinal Cord Disorders |
G37.3 establishes a severe neurological and spinal cord disorder. Due to its chronic and potentially disabling nature, providers must evaluate and document the condition (MEAT criteria: Monitor, Evaluate, Assess, Treat) during an active encounter at least once per calendar year to maintain accurate risk adjustment for Medicare Advantage beneficiaries.
🏥 DRG Assignment
MDC 01 — Diseases and Disorders of the Nervous System
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 097 | Non-Bacterial Infections of Nervous System Except Viral Meningitis with MCC | ~2.10 - 2.30 |
| DRG 098 | Non-Bacterial Infections of Nervous System Except Viral Meningitis with CC | ~1.20 - 1.40 |
| DRG 099 | Non-Bacterial Infections of Nervous System Except Viral Meningitis without CC/MCC | ~0.80 - 0.90 |
Approximate. Verify against IPPS FY2026 Final Rule tables.
🛠️ Commonly Associated CPT Codes (Neurology / Inpatient)
| CPT Code | Description | Modifier Notes / wRVU |
|---|---|---|
| 99223 | Initial hospital inpatient or observation care, per day (High MDM) | Frequently used for the high-complexity admission and diagnostic workup of acute myelopathy. (wRVU: 3.86) |
| 72141 / 72146 | Magnetic resonance (e.g., proton) imaging, spinal canal and contents; without contrast material | Imaging of the cervical (72141) or thoracic (72146) spine to localize the lesion. Billed with Modifier -26 for professional interpretation. |
| 62270 | Spinal puncture, lumbar, diagnostic | Used to evaluate CSF for pleocytosis and oligoclonal bands. If billed alongside an E/M on the same day by the same provider, append Modifier -25 to the E/M code. (wRVU: 2.14) |
💊 Coding Scenarios and Examples
Scenario 1 — Inpatient Admission for Acute Presentation
Clinical Vignette: A 34-year-old male presents to the ED with acute onset of bilateral leg weakness, numbness ascending to the umbilicus, and inability to void for the last 12 hours. Urgent thoracic spine MRI with and without contrast reveals a hyperintense demyelinating lesion from T8 to T10. Lumbar puncture shows mild pleocytosis. A Foley catheter is placed for urinary retention. The neurologist documents “Idiopathic Acute Transverse Myelitis” and initiates high-dose IV methylprednisolone.
Principal Diagnosis:
- G37.3 — Acute transverse myelitis in demyelinating disease of central nervous system (Reason for admission)
Secondary Diagnoses:
- G82.20 — Paraplegia, unspecified (Manifestation)
- R33.9 — Retention of urine, unspecified (Manifestation)
Procedures:
- 99223 — E/M Initial hospital care, High MDM
Scenario 2 — CDI Query: Differentiating MS vs. ATM
Clinical Vignette: A patient is admitted with lower extremity weakness and a sensory level at T4. The attending physician documents: “Acute transverse myelitis. Patient has a known history of relapsing-remitting multiple sclerosis.”
Action / Outcome: Because G37.3 (Acute transverse myelitis) has an Excludes1 note for Multiple Sclerosis (G35.-), they cannot be coded together. The transverse myelitis is considered an exacerbation/manifestation of the multiple sclerosis.
Corrected ICD-10-CM Coding:
- G35.A — Multiple sclerosis (or the highly specific G35.x variant if applicable)
- Do not code G37.3. The MS code fully encompasses the demyelinating event.
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Sequencing Excludes1 Violations. Never code G37.3 on the same claim as a Multiple Sclerosis (G35.-) or Neuromyelitis Optica (G36.0) diagnosis. The broader systemic disease codes take precedence and inherently include the transverse myelitis event. |
| ❌ | Ignoring Manifestations. Failing to code secondary complications like paraplegia or neurogenic bladder leaves the clinical picture incomplete. Capturing these functional deficits (e.g., G82.20) often shifts an inpatient encounter to a higher-weighted DRG by acting as a CC or MCC. |
| ✅ | Query for Underlying Cause. If a patient is admitted with “Transverse myelitis NOS,” ensure the provider’s workup (e.g., AQP4 antibody testing, brain MRI) is monitored. If the diagnosis evolves to NMO or MS during the stay, update the coding prior to billing. |
| ✅ | Capture Annually for Risk Adjustment. For patients who have survived an acute ATM event but have permanent, residual paraparesis requiring ongoing medical management (e.g., catheter care, physical therapy, spasticity management), code G37.3 and the manifestations annually to support the CMS-HCC model.^4 |
📚 Sources
1. CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2025/FY2026. Section I.C.6: Diseases of the Nervous System.2. Transverse Myelitis Consortium Working Group. (2002). Proposed diagnostic criteria and nosology of acute transverse myelitis. Neurology, 59(4), 499-505. (Source for clinical presentation and pathophysiology).
3. Beh, S. C., et al. (2013). Transverse myelitis. Neurologic Clinics, 31(1), 79-138.
4. CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings.
5. American Medical Association (AMA). CPT Professional Edition 2025. Evaluation and Management / Surgery Guidelines.