A86 vs A88
A86 and A88 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on A88
viral encephalitis NOS (A86)
A86
Unspecified viral encephalitis
BillableUnspecified
- Chapter 1
- Certain infectious and parasitic diseases
- Section
- A80-A89
Use when the record says
- Viral encephalomyelitis NOS
- Viral meningoencephalitis NOS
Indexed under
- Encephalitis › acute (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › endemic (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › epidemic NEC (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › infectiousNEC (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
- Encephalitis › postviral NEC (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
A88
Other viral infections of central nervous system, not elsewhere classified
Not billable
- Chapter 1
- Certain infectious and parasitic diseases
- Section
- A80-A89
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027