G04Encephalitis, myelitis and encephalomyelitis

G04 is the ICD-10-CM diagnosis code for encephalitis, myelitis and encephalomyelitis. It belongs to block G00-G09 (inflammatory diseases of the central nervous system) and chapter 6 (diseases of the nervous system). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: G04.0 ((ADEM)), G04.1 (paraplegia), G04.2 (classified), G04.3 (encephalopathy), G04.8 (encephalomyelitis) and G04.9 (unspecified).

Don't report G04 together with the conditions in its Excludes1 note: encephalopathy NOS (G93.40).

The conditions in its Excludes2 note aren't part of G04, but may be coded alongside it if the patient has both: acute transverse myelitis (G37.3), alcoholic encephalopathy (G31.2), multiple sclerosis (G35-), myalgic encephalomyelitis (G93.32) and 3 more.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.