A81

Header — not billable

Atypical virus infections of central nervous system

The ICD-10 code for atypical virus infections of central nervous system is A81.

A81 is a non-billable header code. It groups related conditions but cannot be used on its own for reimbursement — select one of the 5 more specific codes below.

Clinical notes

Includes

Terms listed here further define or give examples of the conditions grouped under this code — they describe what the code covers, not a separate diagnosis.

diseases of the central nervous system caused by prions

Use additional code

This code represents an underlying condition. When a related manifestation is also present, coding convention calls for an additional code to be listed after this one.

code, if applicable, to identify:
dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4)
dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)
dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)
dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)
dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0)
mild neurocognitive disorder due to known physiological condition (F06.7-)

Documentation support

General coding-documentation guidance — not a substitute for payer-specific requirements or professional coding judgment.

•This is a non-billable header code. Documentation must support a more specific child code before this diagnosis can be reported on a claim.
•If the associated manifestation or related condition noted above is also documented, an additional code should be reported alongside this one.
•As a general rule, code to the highest level of specificity supported by the documentation in the medical record.

A81

Clinical notes

Includes

Use additional code

Documentation support

Child codes under A81

Related codes in this category