2026 ICD-10-CM Diagnosis Code A81.1Subacute sclerosing panencephalitis

ICD-10-CM Codes›A00–B99›A80-A89›A81

ICD-10-CM A81.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A81.1 is a billable ICD-10-CM diagnosis code for subacute sclerosing panencephalitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis and Viral infection.

Code Identity

ICD-10-CM Code
A81.1
Billable Status
Yes — Valid for Submission
Code Describes
Subacute sclerosing panencephalitis
Short Description
Subacute sclerosing panencephalitis
Same as the full description in the CMS dataset.
Parent Code
A81
Atypical virus infections of central nervous system

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA80-A89Viral and prion infections of the central nervous system
CategoryA81Atypical virus infections of central nervous system
This CodeA81.1Subacute sclerosing panencephalitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chronic infectious disease of central nervous system
  • Dementia associated with viral encephalitis
  • Dementia due to subacute sclerosing panencephalitis
  • Measles of the central nervous system
  • Morbillivirus encephalitis
  • Paramyxoviridae encephalitis
  • Post measles encephalitis
  • Post-infectious encephalitis
  • Sequela of infection caused by Morbillivirus
  • Subacute sclerosing panencephalitis
  • Van Bogaert's sclerosing leukoencephalitis
  • White matter disorder caused by infection

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Dawson's inclusion body encephalitis
  • Van Bogaert's sclerosing leukoencephalopathy

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Bodechtel-Guttman disease(subacute sclerosing panencephalitis)
    • Dawson's(inclusion body) encephalitis
    • Disease, diseased
      • Bodechtel-Guttmann (subacute sclerosing panencephalitis)
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • Dawson's (inclusion body)
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • diffuse sclerosing
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • inclusion body
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • subacute sclerosing
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • van Bogaert's
    • Leukoencephalitis
      • subacute sclerosing
    • Leukoencephalitis
      • van Bogaert's (sclerosing)
    • Leukoencephalopathy
      • van Bogaert's (sclerosing)
    • Panencephalitis, subacute, sclerosing
    • Van Bogaert's leukoencephalopathy(sclerosing) (subacute)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Subacute Sclerosing Panencephalitis

    a rare, slowly progressive encephalitis caused by chronic infection with the measles virus. the condition occurs primarily in children and young adults, approximately 2-8 years after the initial infection. a gradual decline in intellectual abilities and behavioral alterations are followed by progressive myoclonus; muscle spasticity; seizures; dementia; autonomic dysfunction; and ataxia. death usually occurs 1-3 years after disease onset. pathologic features include perivascular cuffing, eosinophilic cytoplasmic inclusions, neurophagia, and fibrous gliosis. it is caused by the sspe virus, which is a defective variant of measles virus. (from adams et al., principles of neurology, 6th ed, pp767-8)

Patient EducationClinical

Degenerative Nerve Diseases

Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A81.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
046.2 Subac scleros panenceph
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A81.1Overview

Is A81.1 (Atypical virus infections of central nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report subacute sclerosing panencephalitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of A81.1?

Under the General Equivalence Mappings, subacute sclerosing panencephalitis converts to ICD-9-CM 046.2 (subac scleros panenceph). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.