ICD-10 code for equine encephalomyelitis

The ICD-10-CM code for equine encephalomyelitis is A83.9 (Mosquito-borne viral encephalitis, unspecified). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on A83.9.

Within A83, choose A83.9 (unspecified) only when documentation doesn't support a more specific option: Japanese encephalitis (A83.0), Western equine encephalitis (A83.1), Eastern equine encephalitis (A83.2), St Louis encephalitis (A83.3), Australian encephalitis (A83.4), California encephalitis (A83.5), Rocio virus disease (A83.6) and other mosquito-borne viral encephalitis (A83.8).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, relative weight 5.7444), DRG 024 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC, relative weight 3.9708), DRG 097 (Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC, relative weight 3.8226), DRG 098 (Non-Bacterial Infection of Nervous System Except Viral Meningitis with CC, relative weight 2.2706) and DRG 099 (Non-Bacterial Infection of Nervous System Except Viral Meningitis without CC/MCC, relative weight 1.5256), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.