Varicella encephalitis and encephalomyelitis

This code identifies inflammation of the brain (encephalitis) and/or spinal cord (encephalomyelitis) specifically caused by the varicella-zoster virus, commonly known as chickenpox. It represents a severe neurological complication that can arise from a primary varicella infection.

Apply this code when documentation clearly indicates a diagnosis of encephalitis or encephalomyelitis directly attributed to varicella. This typically occurs in patients with a recent or active chickenpox infection who subsequently develop neurological symptoms such as seizures, altered mental status, or focal neurological deficits.

• Ensure the physician explicitly links the neurological condition to varicella; avoid assuming causation.
• Do not use this code for postherpetic neuralgia or other neurological complications of herpes zoster (shingles); those have separate codes.
• Always sequence this code as the primary diagnosis if it is the reason for the encounter, followed by any associated neurological manifestations.