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v1.0.0
ICD-10 Guide
ICD-10 CodesG04.9

G04.9

Billable

Encephalitis, myelitis and encephalomyelitis, unspecified

BILLABLE STATUSYes
IMPLEMENTATION DATEOctober 1, 2015
LAST UPDATED09/05/2025

Code Description

ICD-10 G04.9 is a billable code used to indicate a diagnosis of encephalitis, myelitis and encephalomyelitis, unspecified.

Key Diagnostic Point:

Encephalitis, myelitis, and encephalomyelitis are inflammatory conditions affecting the central nervous system (CNS). Encephalitis refers specifically to inflammation of the brain, while myelitis pertains to inflammation of the spinal cord. Encephalomyelitis encompasses both conditions, indicating inflammation of the brain and spinal cord simultaneously. The unspecified designation indicates that the specific cause of the inflammation is not determined, which can complicate diagnosis and treatment. Common etiologies include viral infections (e.g., herpes simplex virus, West Nile virus), bacterial infections, autoimmune responses, and post-infectious syndromes. Symptoms may range from mild flu-like signs to severe neurological deficits, including seizures, altered consciousness, and motor dysfunction. Diagnosis typically involves clinical evaluation, imaging studies (like MRI), and sometimes lumbar puncture for cerebrospinal fluid analysis. Treatment is often supportive, focusing on managing symptoms and addressing the underlying cause when identified. Given the potential for serious complications, timely recognition and intervention are critical.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variety of potential underlying causes (viral, bacterial, autoimmune)
  • Need for differential diagnosis with other CNS conditions
  • Variability in clinical presentation and severity
  • Potential for co-infections or complications

Audit Risk Factors

  • Insufficient documentation of clinical findings
  • Lack of specificity regarding the cause of encephalitis/myelitis
  • Inconsistent coding practices among providers
  • Failure to document co-existing conditions

Specialty Focus

Medical Specialties

Neurology

Documentation Requirements

Detailed neurological examination findings, imaging results, and laboratory tests.

Common Clinical Scenarios

Patients presenting with seizures, altered mental status, or focal neurological deficits.

Billing Considerations

Ensure documentation reflects the acute nature of symptoms and any differential diagnoses considered.

Infectious Disease

Documentation Requirements

History of exposure, laboratory confirmation of infectious agents, and treatment response.

Common Clinical Scenarios

Patients with suspected viral or bacterial CNS infections requiring specialized testing.

Billing Considerations

Document any travel history or exposure to infectious agents that may clarify the etiology.

Coding Guidelines

Inclusion Criteria

Use G04.9 When
  • Follow ICD
  • CM guidelines for coding encephalitis, myelitis, and encephalomyelitis
  • Ensure that the documentation supports the diagnosis and that any specific etiology is noted when available
  • Use additional codes to capture any underlying conditions or complications

Exclusion Criteria

Do NOT use G04.9 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

62270CPT Code

Lumbar puncture

Clinical Scenario

Used to obtain cerebrospinal fluid for analysis in suspected encephalitis cases.

Documentation Requirements

Document indication for lumbar puncture and results of CSF analysis.

Specialty Considerations

Neurologists should ensure that the procedure is justified based on clinical findings.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of CNS infections, improving the ability to track and analyze these conditions. G04.9 serves as a catch-all for unspecified cases, but the increased granularity in ICD-10 encourages more precise coding when possible.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of CNS infections, improving the ability to track and analyze these conditions. G04.9 serves as a catch-all for unspecified cases, but the increased granularity in ICD-10 encourages more precise coding when possible.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of CNS infections, improving the ability to track and analyze these conditions. G04.9 serves as a catch-all for unspecified cases, but the increased granularity in ICD-10 encourages more precise coding when possible.

Resources

Clinical References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Coding & Billing References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Frequently Asked Questions

When should I use G04.9 instead of a more specific code?

Use G04.9 when the specific cause of encephalitis, myelitis, or encephalomyelitis is not determined or documented. If a specific etiology is known, select the appropriate code that reflects that condition.