ICD-10-CM 2027 diagnosis code
G31.8Other specified degenerative diseases of nervous system
G31.8 is a header code, so it can't be reported by itself. Choose one of the 9 more specific codes beneath it.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About G31.8
G31.8 is the ICD-10-CM diagnosis code for other specified degenerative diseases of nervous system. It belongs to category G31 (other degenerative diseases of nervous system, not elsewhere classified), block G30-G32 (other degenerative diseases of the nervous system) and chapter 6 (diseases of the nervous system). It is a header code, so it can't be reported by itself; one of its 9 subcodes must be used instead.
Within G31, choose G31.8 (Other specified degenerative diseases of nervous system) 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 degenerative disease of nervous system, unspecified (G31.9).
To report this condition, pick the subcode that matches the documentation: G31.80 (unspecified), G31.81 (disease), G31.82 (disease), G31.83 (bodies), G31.84 (etiology), G31.85 (degeneration), G31.86 (disease), G31.87 (speech) and 1 more.
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 has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Specific codes under G31.8
- G31.80Leukodystrophy, unspecifiedBillable
- G31.81Alpers diseaseBillable
- G31.82Leigh's diseaseBillable
- G31.83Neurocognitive disorder with Lewy bodiesBillable
- G31.84Mild cognitive impairment of uncertain or unknown etiologyBillable
- G31.85Corticobasal degenerationBillable
- G31.86Alexander diseaseBillable
- G31.87Primary progressive apraxia of speechBillable
- G31.89Other specified degenerative diseases of nervous systemBillable
Notes that apply from higher levels
Instructions written at a parent level also apply to G31.8.
› From G31 Other degenerative diseases of nervous system, not elsewhere classified
- Reye's syndrome (G93.7)
- 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-)
Broader instructions also apply from Chapter 6: Diseases of the nervous system.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about G31.8
Is G31.8 billable?
- No. G31.8 is a header code. Report one of its more specific subcodes instead.