G91 vs Q07

G91 (Hydrocephalus) compared with Q07 (Other congenital malformations of nervous system), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.

Can these codes be reported together?

No — do not report together. G91 carries an Excludes1 note covering Q07: “Arnold-Chiari syndrome with hydrocephalus (Q07.-)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Side by side

	G91Hydrocephalus	Q07Other congenital malformations of nervous system
Billing status	Non-billable header Report instead: G91.0, G91.1, G91.2, G91.3, G91.4	Non-billable header Report instead: Q07.00, Q07.01, Q07.02, Q07.03, Q07.8
Classification	G00-G99 — Diseases of the Nervous System (G00-G99)	Q00-Q99 — Congenital Malformations, Deformations and Chromosomal Abnormalities (Q00-Q99)
Definition	Hydrocephalus is a non-billable ICD-10-CM category code (G91).	Other congenital malformations of nervous system is a non-billable ICD-10-CM category code (Q07).
Includes	acquired hydrocephalus	—

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources