G04.02 — Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis
Is G04.02 billable?
Yes — G04.02 is billable for FY2027. G04.02 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. G04.02 may be submitted for encounters from October 1, 2026 through September 30, 2027.
G04.02 at a glance
| Code | G04.02 |
|---|---|
| Description | Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does G04.02 group to?
G04.02 sits in MDC 01 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 023Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulatorsurgical
- 024Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCCsurgical
As a secondary diagnosis, G04.02 is a major complication or comorbidity (MCC), which can move a stay into a higher-paying DRG.
How is G04.02 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to G04.02. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Encephalitis › following vaccination or other immunization procedure (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › postimmunization (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › postvaccinal (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalomyelitis › postvaccinal
- Leukoencephalopathy › postimmunization and postvaccinal
- Meningoencephalomyelitis › postimmunization or postvaccination
- Myelitis › postimmunization (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)
- Myelitis › postvaccinal (acute) (ascending) (childhood) (chronic) (descending) (diffuse) (disseminated) (idiopathic) (pressure) (progressive) (spinal cord) (subacute)
- Complication › vaccination › encephalitis or encephalomyelitis (s) (from) (of)
- Complication › vaccination › myelitis (s) (from) (of)
- Encephalitis › due to › smallpox inoculation (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalomyelitis › acute disseminated › postimmunization
Use additional code
Report an additional code alongside G04.02 to fully describe the condition. G04.02 is sequenced first.
Inclusion terms
Alternative wording in documentation that is classified to G04.02.
- Encephalitis, post immunization
- Encephalomyelitis, post immunization
Excludes1 — never code together — inherited from G04
The conditions below can never be reported together with G04.02 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- encephalopathy NOS (G93.40)
Excludes1 — never code together — inherited from G04.0
The conditions below can never be reported together with G04.02 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes2 — not included here — inherited from Chapter 6
The conditions below are not part of G04.02, but a patient may have both at the same time. When documentation supports it, G04.02 and the excluded code may both be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Excludes2 — not included here — inherited from G04
The conditions below are not part of G04.02, but a patient may have both at the same time. When documentation supports it, G04.02 and the excluded code may both be reported.
How long has G04.02 existed?
G04.02 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.