G04.01 – Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)

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

Billable code

ICD-10-CM code G04.01

Code: G04.01 (claims format: G0401)
Description: Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)
Short description: Postinfect acute dissem encephalitis and encephalomyelitis
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 › G04.0

Notes for G04.01

Excludes1 (not coded here):

post chickenpox encephalitis (B01.1)
post measles encephalitis (B05.0)
post measles myelitis (B05.1)

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)

G04.0 – Acute disseminated encephalitis and encephalomyelitis (ADEM)

Excludes1 (not coded here):

acute necrotizing hemorrhagic encephalopathy (G04.3-)
other noninfectious acute disseminated encephalomyelitis (noninfectious ADEM) (G04.81)

Index terms for G04.01

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

Related codes in G04.0

Frequently asked questions

What is ICD-10 code G04.01?

G04.01 is the ICD-10-CM code for postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM), in the block G00-G09 (Inflammatory diseases of the central nervous system).

Is G04.01 a billable code?

Yes. G04.01 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does G04.01 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.