Encephalitis, myelitis and encephalomyelitis (G04) ICD-10-CM
The G04 code range covers encephalitis, myelitis and encephalomyelitis with 19 ICD-10-CM diagnosis codes. 14 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- acute ascending myelitis
- meningoencephalitis
- meningomyelitis
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- encephalopathy NOS G93.40
Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Codes in the G04 Range 19 codes · 14 billable
- G04 Encephalitis, myelitis and encephalomyelitisNon-billable
- G04.0 Acute disseminated encephalitis and encephalomyelitis (ADEM)Non-billable
- 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
- G04.3 Acute necrotizing hemorrhagic encephalopathyNon-billable
- 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
- G04.8 Other encephalitis, myelitis and encephalomyelitisNon-billable
- G04.81 Other encephalitis and encephalomyelitis
- G04.82 Acute flaccid myelitis
- G04.89 Other myelitis
- G04.9 Encephalitis, myelitis and encephalomyelitis, unspecifiedNon-billable
- G04.90 Encephalitis and encephalomyelitis, unspecified
- G04.91 Myelitis, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the G04 range.
Acute Flaccid Myelitis
An acute onset of focal limb weakness that is associated mainly with gray matter abnormalities or CSF pleocytosis, but which is without an apparent cause.
Encephalitis
Inflammation of the BRAIN due to infection, autoimmune processes, toxins, and other conditions. Viral infections (see ENCEPHALITIS, VIRAL) are a relatively frequent cause of this condition.
Encephalomyelitis
A general term indicating inflammation of the BRAIN and SPINAL CORD, often used to indicate an infectious process, but also applicable to a variety of autoimmune and toxic-metabolic conditions. There is significant overlap regarding the usage of this term and ENCEPHALITIS in the literature.
Meningoencephalitis
An inflammatory process involving the brain (ENCEPHALITIS) and meninges (MENINGITIS), most often produced by pathogenic organisms which invade the central nervous system, and occasionally by toxins, autoimmune disorders, and other conditions.
Myelitis
Inflammation of the spinal cord. Relatively common etiologies include infections; AUTOIMMUNE DISEASES; SPINAL CORD; and ischemia (see also SPINAL CORD VASCULAR DISEASES). Clinical features generally include weakness, sensory loss, localized pain, incontinence, and other signs of autonomic dysfunction.
Paraparesis, Tropical Spastic
A subacute paralytic myeloneuropathy occurring endemically in tropical areas such as the Caribbean, Colombia, India, and Africa, as well as in the southwestern region of Japan; associated with infection by HUMAN T-CELL LEUKEMIA VIRUS I. Clinical manifestations include a slowly progressive spastic weakness of the legs, increased reflexes, Babinski signs, incontinence, and loss of vibratory and position sensation. On pathologic examination inflammatory, demyelination, and necrotic lesions may be found in the spinal cord. (Adams et al., Principles of Neurology, 6th ed, p1239)
About the G04 Code Range
Inflammation of the brain, spinal cord, or both appears here as encephalitis, myelitis, or encephalomyelitis.
G04.0 identifies acute disseminated forms and separates postinfectious, postimmunization, and unspecified cases. G04.3 makes those distinctions for acute necrotizing hemorrhagic encephalopathy and also has an other category. Separate branches identify tropical stiff leg paralysis (G04.1) and bacterial inflammation involving the brain or spinal cord (G04.2).
The other and unspecified branches distinguish brain involvement from spinal cord involvement. G04.8 also identifies acute flaccid myelitis, meaning sudden spinal cord inflammation described as limp.
Questions About This Page
How many billable codes are in the G04 range?
Of the 19 codes in this range, 14 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the G04 range classify?
The range classifies encephalitis, myelitis and encephalomyelitis. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
