ICD-10-CM 2027
ICD-10 code for cerebellar hemiatrophy
From the official ICD-10-CM alphabetic index entry “Hemiatrophy › cerebellar”. Page updated September 29, 2026.
About coding cerebellar hemiatrophy
The ICD-10-CM code for cerebellar hemiatrophy is G31.9 (Degenerative disease of nervous system, unspecified).
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.
Common questions about cerebellar hemiatrophy ICD-10 codes
What is the ICD-10 code for cerebellar hemiatrophy?
- G31.9 — Degenerative disease of nervous system, unspecified.
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.