ICD-10-CM 2027
ICD-10 code for brain atrophy
From the official ICD-10-CM alphabetic index entry “Atrophy, atrophic (of) › brain (cortex) (progressive)”. Page updated September 29, 2026.
About coding brain atrophy
The ICD-10-CM code for brain atrophy is G31.9 (Degenerative disease of nervous system, unspecified). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on G31.9.
Within G31, choose G31.9 (Degenerative disease of nervous system, unspecified) only when documentation doesn't support a more specific option: frontotemporal dementia (G31.0), senile degeneration of brain, not elsewhere classified (G31.1), degeneration of nervous system due to alcohol (G31.2) and other specified degenerative diseases of nervous system (G31.8).
Use an additional code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify: dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4), dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-), dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3), dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2), dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0) and 1 more.
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
More specific brain atrophy codes (official index)
Common questions about brain atrophy ICD-10 codes
What is the ICD-10 code for brain atrophy?
- G31.9 — Degenerative disease of nervous system, unspecified. More specific codes apply when the documentation supports them: G31.01, G31.01, G31.1.
What is the ICD-10 code for frontotemporal circumscribed brain atrophy?
- G31.01 — Pick's disease.
What is the ICD-10 code for senile nec brain atrophy?
- G31.1 — Senile degeneration of brain, not elsewhere classified.
Is G31.9 billable?
- Yes. G31.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G31.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G31.9 as a principal diagnosis.
Is G31.9 a CC or MCC?
- No. G31.9 is neither a CC nor an MCC under MS-DRG v44.0.