G04.0Acute disseminated encephalitis and encephalomyelitis (ADEM)

G04.0 is the ICD-10-CM diagnosis code for acute disseminated encephalitis and encephalomyelitis (ADEM). It belongs to category G04 (encephalitis, myelitis and encephalomyelitis), 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 3 subcodes must be used instead.

Within G04 (encephalitis, myelitis and encephalomyelitis), G04.0 is specifically for acute disseminated encephalitis and encephalomyelitis (ADEM). Related codes cover tropical spastic paraplegia (G04.1), bacterial meningoencephalitis and meningomyelitis, not elsewhere classified (G04.2), acute necrotizing hemorrhagic encephalopathy (G04.3), other encephalitis, myelitis and encephalomyelitis (G04.8) and unspecified (G04.9).

To report this condition, pick the subcode that matches the documentation: G04.00 (unspecified), G04.01 (ADEM)) and G04.02 (encephalomyelitis).

Don't report G04.0 together with the conditions in its Excludes1 note: acute necrotizing hemorrhagic encephalopathy (G04.3-) and other noninfectious acute disseminated encephalomyelitis (noninfectious ADEM) (G04.81).

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