ICD-10-CM 2027
ICD-10 code for brain degeneration
From the official ICD-10-CM alphabetic index entry “Degeneration, degenerative › brain (cortical) (progressive)”. Page updated September 29, 2026.
About coding brain degeneration
The ICD-10-CM code for brain degeneration is G31.9 (Degenerative disease of nervous system, unspecified). The official index lists 21 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 degeneration codes (official index)
- alcoholic G31.2 — Degeneration of nervous system due to alcohol
- arteriosclerotic I67.2 — Cerebral atherosclerosis
- childhood G31.9 — Degenerative disease of nervous system, unspecified
- specified NEC G31.89 — Other specified degenerative diseases of nervous system
- cystic G31.89 — Other specified degenerative diseases of nervous system
- congenital Q04.6 — Congenital cerebral cysts
- in
- alcoholism G31.2 — Degeneration of nervous system due to alcohol
- beriberi E51.2 — Wernicke's encephalopathy
- cerebrovascular disease I67.9 — Cerebrovascular disease, unspecified
- congenital hydrocephalus Q03.9 — Congenital hydrocephalus, unspecified
- with spina bifida
- Fabry-Anderson disease E75.21 — Fabry (-Anderson) disease
- Gaucher's disease E75.22 — Gaucher disease
- Hunter's syndrome E76.1 — Mucopolysaccharidosis, type II
- lipidosis
- cerebral E75.4 — Neuronal ceroid lipofuscinosis
- generalized E75.6 — Lipid storage disorder, unspecified
- mucopolysaccharidosis
- myxedema E03.9 — Hypothyroidism, unspecified
- neoplastic disease D49.6 — Neoplasm of unspecified behavior of brain
- Niemann-Pick disease E75.249 — Niemann-Pick disease, unspecified
- sphingolipidosis E75.3 — Sphingolipidosis, unspecified
- vitamin B12 deficiency E53.8 — Deficiency of other specified B group vitamins
- senile NEC G31.1 — Senile degeneration of brain, not elsewhere classified
Common questions about brain degeneration ICD-10 codes
What is the ICD-10 code for brain degeneration?
- G31.9 — Degenerative disease of nervous system, unspecified. More specific codes apply when the documentation supports them: G31.2, I67.2, G31.9, G31.89 and others below.
What is the ICD-10 code for alcoholic brain degeneration?
- G31.2 — Degeneration of nervous system due to alcohol.
What is the ICD-10 code for arteriosclerotic brain degeneration?
- I67.2 — Cerebral atherosclerosis.
What is the ICD-10 code for childhood brain degeneration?
- G31.9 — Degenerative disease of nervous system, unspecified.
What is the ICD-10 code for cystic brain degeneration?
- G31.89 — Other specified degenerative diseases of nervous system.
What is the ICD-10 code for senile nec brain degeneration?
- 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.