G31.9 Degenerative disease of nervous system, unspecified

Billable ICD-10-CM code, FY2026.

Applies from G31 Other degenerative diseases of nervous system, not elsewhere classified

Excludes2 (not included here)

• Reye's syndrome (G93.7)

Use additional code

• 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)
• mild neurocognitive disorder due to known physiological condition (F06.7-)

Risk adjustment (HCC)

• RxHCC V08: HCC 112 — Dementia, Except Alzheimer's Disease
• ESRD V24: HCC 52

MS-DRG index

Defines the logic of DRG(s) 056-057 in MDC 01.

Approximate ICD-9-CM (GEMs)

• 330.9 Unspecified cerebral degeneration in childhood (approximate)
• 331.9 Cerebral degeneration, unspecified (approximate)

Code annotations containing back-references to G31.9

Back-references to G31.9

• Type 1 Excludes: F06.7 Mild neurocognitive disorder due to known physiological condition ("cerebral degeneration (G31.9)")
• Use Additional: G31 Other degenerative diseases of nervous system, not elsewhere classified ("code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify:")
• Type 1 Excludes: G31.84 Mild cognitive impairment of uncertain or unknown etiology ("cerebral degeneration (G31.9)")

Diagnosis Index entries for G31.9

• Atrophy, atrophic (of) › brain (cortex) (progressive)
• Degeneration, degenerative › brain (cortical) (progressive)
• Degeneration, degenerative › brain (cortical) (progressive) › childhood
• Degeneration, degenerative › cerebellar NOS
• Degeneration, degenerative › nervous system
• Hemiatrophy › cerebellar

Nearby codes

• G31.84 Mild cognitive impairment of uncertain or unknown etiology
• G31.85 Corticobasal degeneration
• G31.86 Alexander disease
• G31.87 Primary progressive apraxia of speech
• G31.89 Other specified degenerative diseases of nervous system
• G31.9 Degenerative disease of nervous system, unspecified (this code)