ICD-10 Code A81.89 – Other atypical virus infections of central nervous system (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A81.89 – Other atypical virus infections of central nervous system
What it is
This code identifies an atypical viral infection affecting the central nervous system that is not classified elsewhere. Use it when the provider documents a specific atypical viral cause involving the brain, spinal cord, or meninges.
Clinical signs
Clinical features vary; refer to documentation. Common neurologic findings may include altered mental status, seizures, focal deficits, meningitis, or encephalitis patterns when a viral CNS infection is confirmed.
When to use this code
Use A81.89 when the record clearly states an atypical viral infection of the central nervous system and no more specific code applies. It is appropriate for documented viral CNS disease that is not otherwise indexed or classified. If the organism is named, verify whether a different code is more specific.
Do not use for
Do not use this code for common viral meningitis or encephalitis when a more specific diagnosis is documented. Also avoid it when the chart does not confirm a viral CNS infection; check documentation.
Coding tip
Code the most specific viral CNS diagnosis available, and use A81.89 only when the provider documents an atypical viral infection without a better option.