G04.90 – Encephalitis and encephalomyelitis, unspecified

ICD-10-CM 2027 diagnosis code · Inflammatory diseases of the central nervous system

Billable code

ICD-10-CM code G04.90

Code: G04.90 (claims format: G0490)
Description: Encephalitis and encephalomyelitis, unspecified
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 6. Diseases of the nervous system (G00-G99)
Block: G00-G09 Inflammatory diseases of the central nervous system
Parent codes: G04 › G04.9

Notes for G04.90

Applicable to:

Ventriculitis (cerebral) NOS

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

G04 – Encephalitis, myelitis and encephalomyelitis

Includes:

acute ascending myelitis
meningoencephalitis
meningomyelitis

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)

Index terms for G04.90

Entries in the ICD-10-CM alphabetic index that lead to this code:

Related codes in G04.9

G04.91 – Myelitis, unspecifiedBillable

Frequently asked questions

What is ICD-10 code G04.90?

G04.90 is the ICD-10-CM code for encephalitis and encephalomyelitis, unspecified, in the block G00-G09 (Inflammatory diseases of the central nervous system).

Is G04.90 a billable code?

Yes. G04.90 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does G04.90 belong to?

It belongs to category G04 – Encephalitis, myelitis and encephalomyelitis.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.