ICD-10 Code A81.8 – Other atypical virus infections of central nervous system (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A81.8 – Other atypical virus infections of central nervous system
What it is
A81.8 identifies atypical viral infections affecting the central nervous system that do not fit a more specific ICD-10 category. Use it for uncommon viral CNS diseases when the organism or syndrome is documented but not otherwise classified.
Clinical signs
Clinical features vary; refer to documentation. Common CNS findings may include encephalitis, meningitis, altered mental status, seizures, focal neurologic deficits, or other signs of brain or spinal cord involvement.
When to use this code
Use A81.8 when the provider documents an atypical viral infection of the CNS and no more specific code is available. It is appropriate when the record supports viral involvement of the central nervous system but the exact subtype remains unspecified or uncommon.
If the note names a specific viral disease with a dedicated ICD-10 code, choose that code instead. Check documentation for the confirmed site, organism, and whether the infection is truly central nervous system related.
Do not use for
Do not use this code for common viral meningitis, encephalitis, or other infections that have their own ICD-10 codes. Also avoid it when the chart does not support a CNS infection or when the diagnosis is nonviral.
Coding tip
Code A81.8 only after confirming the provider documented an atypical viral CNS infection and no more specific ICD-10 option applies.