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ICD-10-CM 2027 diagnosis code

G31.84Mild cognitive impairment of uncertain or unknown etiology

✓ Billable / specific

G31.84 is a valid, billable ICD-10-CM code for mild cognitive impairment of uncertain or unknown etiology. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Mild cognitive impairment, ICD-10 code for Mild neurocognitive disorder.

Code last changed in FY2023 (effective October 1, 2022). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G31.84

G31.84 is the ICD-10-CM diagnosis code for mild cognitive impairment of uncertain or unknown etiology. 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 billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G31.8 (other specified degenerative diseases of nervous system), G31.84 is specifically for mild cognitive impairment of uncertain or unknown etiology. Related codes cover leukodystrophy, unspecified (G31.80), Alpers disease (G31.81), Leigh's disease (G31.82), neurocognitive disorder with Lewy bodies (G31.83), Corticobasal degeneration (G31.85), Alexander disease (G31.86), primary progressive apraxia of speech (G31.87) and other specified degenerative diseases of nervous system (G31.89).

Don't report G31.84 together with the conditions in its Excludes1 note: age related cognitive decline (R41.81), altered mental status (R41.82), cerebral degeneration (G31.9), cerebrovascular diseases (I60-I69) and 7 more.

Use an additional code to identify presence of: alcohol abuse and dependence (F10.-), exposure to environmental tobacco smoke (Z77.22), history of tobacco dependence (Z87.891), hypertension (I10-I1A), occupational exposure to environmental tobacco smoke (Z57.31) and 2 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 is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015, and changed in FY2023 (title revised).

Before ICD-10, this condition was coded in ICD-9-CM as 331.83 (mild cognitive impairment, so stated).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Mild cognitive disorder NOS
  • Mild neurocognitive disorder of uncertain or unknown etiology
Excludes1Not coded here — never report together with this code
  • age related cognitive decline (R41.81)
  • altered mental status (R41.82)
  • cerebral degeneration (G31.9)
  • cerebrovascular diseases (I60-I69)
  • change in mental status (R41.82)
  • cognitive deficits following (sequelae of) cerebral hemorrhage or infarction (I69.01-, I69.11-, I69.21-, I69.31-, I69.81-, I69.91-)
  • cognitive impairment due to intracranial or head injury (S06.-)
  • dementia (F01.-, F02.-, F03.-)
  • mild neurocognitive disorder due to a known physiological condition (F06.7-)
  • neurologic neglect syndrome (R41.4)
  • personality change, nonpsychotic (F68.8)
Use additional codeAdd a secondary code to fully describe the condition
  • code to identify presence of:
  • alcohol abuse and dependence (F10.-)
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • hypertension (I10-I1A)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Notes that apply from higher levels

Instructions written at a parent level also apply to G31.84.

› From G31 Other degenerative diseases of nervous system, not elsewhere classified
Excludes2
Use additional code

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Alphabetic index entries

5 entries

Terms in the official ICD-10-CM index that lead to G31.84.

Codes whose notes reference G31.84

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 331.83Mild cognitive impairment, so statedexact

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • FY2023 (effective 10/1/2022): Title revised — was “Mild cognitive impairment, so stated”

Common questions about G31.84

Is G31.84 billable?

Yes. G31.84 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can G31.84 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict G31.84 as a principal diagnosis.

Is G31.84 a CC or MCC?

No. G31.84 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does G31.84 group to?

G31.84 is used in the MS-DRG v44.0 logic for MS-DRG 056 (Degenerative Nervous System Disorders with MCC) and MS-DRG 057 (Degenerative Nervous System Disorders without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for G31.84?

The CMS General Equivalence Mappings map G31.84 to ICD-9-CM 331.83.