ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview

The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group G04 includes inflammatory diseases of the central nervous system such as encephalitis, myelitis, and encephalomyelitis caused by infectious, autoimmune, or unspecified etiologies that affect the brain and/or spinal cord. These ICD-10-CM diagnosis codes are used to document acute and chronic presentations, capture disease severity, and specify anatomic involvement or identified causative agents when known. Accurate coding within the ICD-10-CM G04 group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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ICD-10-CM G04: Encephalitis, Myelitis And Encephalomyelitis Overview

The ICD-10-CM G04 group encompasses inflammatory disorders of the central nervous system, including encephalitis, myelitis, and encephalomyelitis that affect the brain, spinal cord, or both. These conditions often arise from infectious, autoimmune, or post-infectious processes and can lead to significant neurologic dysfunction. Accurate coding is important because it supports appropriate clinical documentation and reimbursement by reflecting the severity and organ involvement of these diagnoses.

When to Use

Use a code from this group when clinical documentation indicates inflammation of the brain, spinal cord, or both due to infectious, immune-mediated, or unspecified causes. Select the specific code that reflects the documented anatomic involvement, causative organism if identified, and whether the condition is acute, chronic, or recurrent.

ICD-10-CM Codes

14 rows

ICD-10-CM Code	Description
G04.00	Acute disseminated encephalitis and encephalomyelitis, unspecified
G04.01	Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
G04.02	Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis
G04.1	Tropical spastic paraplegia
G04.2	Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified
G04.30	Acute necrotizing hemorrhagic encephalopathy, unspecified
G04.31	Postinfectious acute necrotizing hemorrhagic encephalopathy
G04.32	Postimmunization acute necrotizing hemorrhagic encephalopathy
G04.39	Other acute necrotizing hemorrhagic encephalopathy
G04.81	Other encephalitis and encephalomyelitis
G04.82	Acute flaccid myelitis
G04.89	Other myelitis
G04.90	Encephalitis and encephalomyelitis, unspecified
G04.91	Myelitis, unspecified

DRG Codes

15 rows

DRG Code	Description
023	Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator
024	Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC
052	Spinal Disorders and Injuries with CC/MCC
053	Spinal Disorders and Injuries without CC/MCC
094	Bacterial and Tuberculous Infections of Nervous System with MCC
095	Bacterial and Tuberculous Infections of Nervous System with CC
096	Bacterial and Tuberculous Infections of Nervous System without CC/MCC
097	Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC
098	Non-Bacterial Infection of Nervous System Except Viral Meningitis with CC
099	Non-Bacterial Infection of Nervous System Except Viral Meningitis without CC/MCC
791	Prematurity with Major Problems
793	Full Term Neonate with Major Problems
974	HIV with Major Related Condition with MCC
975	HIV with Major Related Condition with CC
976	HIV with Major Related Condition without CC/MCC

Typical Clinical Scenarios

An adult presents to the emergency department with acute onset fever, severe headache, confusion, and new focal neurologic deficits (right-sided weakness) over the past 48 hours. Lumbar puncture shows lymphocytic pleocytosis and elevated protein, brain MRI demonstrates medial temporal lobe hyperintensity consistent with viral limbic involvement; empiric antiviral therapy is started while diagnostics target herpesviruses. A diagnosis from this group is assigned for acute viral encephalitis affecting the brain parenchyma. Typical codes: G04.00, G04.01
A child with a recent enteroviral infection is evaluated in outpatient neurology for subacute onset of flaccid weakness, sensory changes, and bladder dysfunction evolving over days; MRI of the spinal cord shows longitudinally extensive T2 hyperintensity consistent with myelitis. Because the presentation represents inflammatory myelitis following infection with ongoing motor and autonomic involvement, a central nervous system inflammatory diagnosis from this group is used to capture the spinal cord process. Typical codes: G04.10, G04.2
A hospitalized patient with known autoimmune disease develops new confusion and seizures while receiving immunosuppressive therapy; workup excludes metabolic causes and shows multifocal encephalitis on MRI and cerebrospinal fluid inflammation. The encephalitic process is recorded as a complication in the setting of immunosuppression and treated as inflammatory central nervous system disease to guide care and documentation. Typical codes: G04.81, G04.89

ICD-10-CM Code For Bacterial Meningitis Not Elsewhere Classified: Group Overview

G01-MENINGITIS-IN-BACTERIAL-DISEASES

ICD-10-CM Code For Meningitis In Bacterial Diseases Classified Elsewhere: Group Overview

G02-MENINGITIS-DUE-TO-OTHER-INFECTIONS

ICD-10-CM Code For Meningitis In Other Infectious And Parasitic Diseases Classified Elsewhere: Group Overview

G03-MENINGITIS-DUE-TO-OTHER-CAUSES

ICD-10-CM Code For Meningitis Due To Other And Unspecified Causes: Group Overview

G05-ENCEPHALITIS-MYELITIS-ENCEPHALOMYELITIS

ICD-10-CM Code For Encephalitis Myelitis And Encephalomyelitis In Diseases Classified Elsewhere: Group Overview

G06-INTRACRANIAL-AND-INTRASPINAL-ABSCESS

ICD-10-CM Code For Intracranial And Intraspinal Abscess And Granuloma: Group Overview

G07-INTRACRANIAL-AND-INTRASPINAL-ABSCESS

ICD-10-CM Code For Intracranial And Intraspinal Abscess And Granuloma In Diseases Classified Elsewhere: Group Overview

G08-INTRACRANIAL-AND-INTRASPINAL-PHLEBITIS

ICD-10-CM Code For Intracranial And Intraspinal Phlebitis And Thrombophlebitis: Group Overview

G09-SEQUELAE-OF-CENTRAL-NERVOUS-SYSTEM-INFLAMMATION

ICD-10-CM Code For Sequelae Of Inflammatory Diseases Of Central Nervous System: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

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When to Use

ICD-10-CM Codes

14 rows

ICD-10-CM Code	Description
G04.00	Acute disseminated encephalitis and encephalomyelitis, unspecified
G04.01	Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
G04.02	Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis
G04.1	Tropical spastic paraplegia
G04.2	Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified
G04.30	Acute necrotizing hemorrhagic encephalopathy, unspecified
G04.31	Postinfectious acute necrotizing hemorrhagic encephalopathy
G04.32	Postimmunization acute necrotizing hemorrhagic encephalopathy
G04.39	Other acute necrotizing hemorrhagic encephalopathy
G04.81	Other encephalitis and encephalomyelitis
G04.82	Acute flaccid myelitis
G04.89	Other myelitis
G04.90	Encephalitis and encephalomyelitis, unspecified
G04.91	Myelitis, unspecified

DRG Codes

15 rows

DRG Code	Description
023	Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator
024	Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC
052	Spinal Disorders and Injuries with CC/MCC
053	Spinal Disorders and Injuries without CC/MCC
094	Bacterial and Tuberculous Infections of Nervous System with MCC
095	Bacterial and Tuberculous Infections of Nervous System with CC
096	Bacterial and Tuberculous Infections of Nervous System without CC/MCC
097	Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC
098	Non-Bacterial Infection of Nervous System Except Viral Meningitis with CC
099	Non-Bacterial Infection of Nervous System Except Viral Meningitis without CC/MCC
791	Prematurity with Major Problems
793	Full Term Neonate with Major Problems
974	HIV with Major Related Condition with MCC
975	HIV with Major Related Condition with CC
976	HIV with Major Related Condition without CC/MCC

Typical Clinical Scenarios

An adult presents to the emergency department with acute onset fever, severe headache, confusion, and new focal neurologic deficits (right-sided weakness) over the past 48 hours. Lumbar puncture shows lymphocytic pleocytosis and elevated protein, brain MRI demonstrates medial temporal lobe hyperintensity consistent with viral limbic involvement; empiric antiviral therapy is started while diagnostics target herpesviruses. A diagnosis from this group is assigned for acute viral encephalitis affecting the brain parenchyma. Typical codes: G04.00, G04.01
A child with a recent enteroviral infection is evaluated in outpatient neurology for subacute onset of flaccid weakness, sensory changes, and bladder dysfunction evolving over days; MRI of the spinal cord shows longitudinally extensive T2 hyperintensity consistent with myelitis. Because the presentation represents inflammatory myelitis following infection with ongoing motor and autonomic involvement, a central nervous system inflammatory diagnosis from this group is used to capture the spinal cord process. Typical codes: G04.10, G04.2
A hospitalized patient with known autoimmune disease develops new confusion and seizures while receiving immunosuppressive therapy; workup excludes metabolic causes and shows multifocal encephalitis on MRI and cerebrospinal fluid inflammation. The encephalitic process is recorded as a complication in the setting of immunosuppression and treated as inflammatory central nervous system disease to guide care and documentation. Typical codes: G04.81, G04.89

ICD-10-CM Code For Bacterial Meningitis Not Elsewhere Classified: Group Overview

G01-MENINGITIS-IN-BACTERIAL-DISEASES

ICD-10-CM Code For Meningitis In Bacterial Diseases Classified Elsewhere: Group Overview

G02-MENINGITIS-DUE-TO-OTHER-INFECTIONS

ICD-10-CM Code For Meningitis In Other Infectious And Parasitic Diseases Classified Elsewhere: Group Overview

G03-MENINGITIS-DUE-TO-OTHER-CAUSES

ICD-10-CM Code For Meningitis Due To Other And Unspecified Causes: Group Overview

G05-ENCEPHALITIS-MYELITIS-ENCEPHALOMYELITIS

ICD-10-CM Code For Encephalitis Myelitis And Encephalomyelitis In Diseases Classified Elsewhere: Group Overview

G06-INTRACRANIAL-AND-INTRASPINAL-ABSCESS

ICD-10-CM Code For Intracranial And Intraspinal Abscess And Granuloma: Group Overview

G07-INTRACRANIAL-AND-INTRASPINAL-ABSCESS

ICD-10-CM Code For Intracranial And Intraspinal Abscess And Granuloma In Diseases Classified Elsewhere: Group Overview

G08-INTRACRANIAL-AND-INTRASPINAL-PHLEBITIS

ICD-10-CM Code For Intracranial And Intraspinal Phlebitis And Thrombophlebitis: Group Overview

G09-SEQUELAE-OF-CENTRAL-NERVOUS-SYSTEM-INFLAMMATION

ICD-10-CM Code For Sequelae Of Inflammatory Diseases Of Central Nervous System: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview

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ICD-10-CM G04: Encephalitis, Myelitis And Encephalomyelitis Overview

ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview

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ICD-10-CM G04: Encephalitis, Myelitis And Encephalomyelitis Overview

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

References

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

References

ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview

Sign up for ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview policy alerts

ICD-10-CM G04: Encephalitis, Myelitis And Encephalomyelitis Overview

ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview

Sign up for ICD-10-CM Code For Encephalitis, Myelitis And Encephalomyelitis: Group Overview policy alerts

ICD-10-CM G04: Encephalitis, Myelitis And Encephalomyelitis Overview

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which conditions are included in ICD-10-CM group G04?

How should coders specify causative agents or anatomic involvement within G04 codes?

What are examples of specific codes within the G04 group for postinfectious and postimmunization conditions?

Which DRGs commonly relate to diagnoses in the G04 group?

How does accurate G04 coding impact claims and documentation?

References

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which conditions are included in ICD-10-CM group G04?

How should coders specify causative agents or anatomic involvement within G04 codes?

What are examples of specific codes within the G04 group for postinfectious and postimmunization conditions?

Which DRGs commonly relate to diagnoses in the G04 group?

How does accurate G04 coding impact claims and documentation?

References