ICD-9-CM diagnosis code (retired)
323.9 — Unspecified causes of encephalitis, myelitis, and encephalomyelitis
ICD-9-CM was replaced by ICD-10 on October 1, 2015. These are the ICD-10-CM equivalents from the CMS General Equivalence Mappings.
About ICD-9-CM 323.9
323.9 is an ICD-9-CM diagnosis code for unspecified causes of encephalitis, myelitis, and encephalomyelitis. ICD-9-CM was retired for U.S. claims on October 1, 2015, when ICD-10-CM took over.
The CMS General Equivalence Mappings translate it to 2 ICD-10-CM codes, such as G04.90 (Encephalitis and encephalomyelitis, unspecified) and G04.91 (Myelitis, unspecified). All of these are approximate matches, so review the record to pick the right one.
ICD-10-CM equivalents
Common questions about 323.9
GEMs are a translation aid, not a substitute for coding from the record. The 2027 ICD-10 code set has changed since the last GEMs release in 2018. Page updated September 29, 2026.