Q04.8 vs Q07.0
Q04.8 and Q07.0 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on Q07.0
Arnold-Chiari syndrome, type IV (Q04.8)
Q04.8
Other specified congenital malformations of brain
BillableUnspecified
- Chapter 17
- Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
- Section
- Q00-Q07
Use when the record says
- Arnold-Chiari syndrome, type IV
- Macrogyria
Indexed under
- Macrogyria (congenital)
- Ulegyria
- Arnold-Chiari disease, obstruction or syndrome › type IV (type II)
- Displacement, displaced › brain stem, caudal
- Displacement, displaced › cerebellum, caudal
Q07.0
Arnold-Chiari syndrome
Not billable
- Chapter 17
- Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
- Section
- Q00-Q07
Use when the record says
- Arnold-Chiari syndrome, type II
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027