ICD-10 Code G04.00 – Acute disseminated encephalitis and encephalomyelitis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G04.00 – Acute disseminated encephalitis and encephalomyelitis, unspecified
What it is
G04.00 identifies acute disseminated encephalitis and encephalomyelitis when the record does not specify a cause or further detail. It refers to an inflammatory disorder affecting the brain and spinal cord.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include acute neurologic deficits, altered mental status, and signs of multifocal central nervous system involvement.
When to use this code
Use this code when the clinician documents acute disseminated encephalitis and encephalomyelitis, but does not provide a more specific subtype, cause, or related detail. It is appropriate for confirmed diagnoses in the chart, not for symptoms alone. If the record names another demyelinating or infectious process, code that documented condition instead.
Do not use for
Do not use it for nonspecific encephalopathy, isolated encephalitis, or demyelinating disease without documentation of acute disseminated encephalitis and encephalomyelitis. Check documentation if the diagnosis is uncertain.
Coding tip
Query for specificity when the note says “encephalitis” or “encephalomyelitis” without the acute disseminated term.