G04.90 is the authoritative medical code for Encephalitis and encephalomyelitis, unspecified. This classification is used in medical billing and clinical recording to specify the clinical criteria for encephalitis and encephalomyelitis, unspecified (ICD-10-CM G04.90), ensuring healthcare documentation aligns with 2026 federal coding standards.
Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.
Official Registry Overview & Definition
Encephalitis and encephalomyelitis, unspecified is a billable ICD-10-CM diagnosis code G04.90. Includes: acute ascending myelitis; meningoencephalitis; meningomyelitis. Inclusion terms: Ventriculitis cerebral NOS. Excludes1 (not coded here): encephalopathy NOS G93.40. Excludes2 (not included here): acute transverse myelitis G37.3; alcoholic encephalopathy G31.2; multiple sclerosis G35-; myalgic encephalomyelitis G93.32; subacute necrotizing myelitis G37.4; toxic encephalitis G92.8; toxic encephalopathy G92.8.
Official Tabular Instructional Notes
Sequencing, inclusion, and exclusion notes published for G04.90 in the official ICD-10-CM tabular list.
Includes
Conditions the official ICD-10-CM tabular list includes under this code.
- acute ascending myelitis
- meningoencephalitis
- meningomyelitis
Inclusion Terms
Alternative terms the tabular list files under this code.
- Ventriculitis cerebral NOS
Excludes1 — Not Coded Here
Conditions that can never be reported with this code; the two are mutually exclusive.
- encephalopathy NOS G93.40
Excludes2 — Not Included Here
Conditions not covered by this code, but which may be reported alongside it when both are present.
- acute transverse myelitis G37.3
- alcoholic encephalopathy G31.2
- multiple sclerosis G35-
- myalgic encephalomyelitis G93.32
- subacute necrotizing myelitis G37.4
- toxic encephalitis G92.8
- toxic encephalopathy G92.8
Frequently Asked Questions (FAQ) & Clinical Guidance
What can't be coded together with G04.90?
Per Excludes1 instructions, G04.90 must not be reported with: encephalopathy NOS (G93.40).
Can G04.90 be reported alongside related conditions?
Per Excludes2 instructions, G04.90 and the following may both be reported when both are present: acute transverse myelitis (G37.3); alcoholic encephalopathy (G31.2); multiple sclerosis (G35-); myalgic encephalomyelitis (G93.32).
What conditions are included under G04.90?
Encephalitis and encephalomyelitis, unspecified includes: Ventriculitis (cerebral) NOS.
Codes in This Family (16)
Official ICD-10-CM classifications in the same code family as G04.90, with their registry titles.
- G04 — Encephalitis, myelitis and encephalomyelitis
- G04.0 — Acute disseminated encephalitis and encephalomyelitis (ADEM)
- G04.00 — Acute disseminated encephalitis and encephalomyelitis, unspecified
- G04.01 — Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
- G04.02 — Postimmunization acute disseminated encephalomyelitis (ADEM)
- G04.1 — Tropical spastic paraplegia
- G04.2 — Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified
- G04.3 — Acute necrotizing hemorrhagic encephalopathy
- G04.30 — Acute necrotizing hemorrhagic encephalopathy, unspecified
- G04.31 — Postinfectious acute necrotizing hemorrhagic encephalopathy
- G04.32 — Postimmunization acute necrotizing hemorrhagic encephalopathy
- G04.8 — Other encephalitis, myelitis and encephalomyelitis
- G04.81 — Other encephalitis and encephalomyelitis
- G04.89 — Other myelitis
- G04.9 — Encephalitis, myelitis and encephalomyelitis, unspecified
- G04.91 — Myelitis, unspecified
Indexed Clinical Terms (6)
Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalomyelitis
- Hematomyelitis
- Infection, infected, infective (opportunistic), brain
- Meningoencephalitis
- Ventriculitis (cerebral)
Related Codes & Numerical Sequence (Crawl Map)
Search engines and indexers are advised to traverse adjacent medical codes in this sub-chapter range to find correlated diagnoses or therapeutic procedures: