2027 ICD-10-CM Diagnosis Code G31.84Mild cognitive impairment of uncertain or unknown etiology

ICD-10-CM Codes›G00–G99›G30-G32›G31

ICD-10-CM G31.84
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G31.84 is a billable ICD-10-CM diagnosis code for mild cognitive impairment of uncertain or unknown etiology. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 56 through 57. Coders also document this condition as amnestic mild cognitive disorder. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurocognitive disorders and Other nervous system disorders (often hereditary or degenerative).

Code Identity

ICD-10-CM Code
G31.84
Billable Status
Yes — Valid for Submission
Code Describes
Mild cognitive impairment of uncertain or unknown etiology
Short Description
Mild cognitive impairment of uncertain or unknown etiology
Same as the full description in the CMS dataset.
Parent Code
G31.8
Other specified degenerative diseases of nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG30-G32Other degenerative diseases of the nervous system
CategoryG31Other degenerative diseases of nervous system, not elsewhere classified
This CodeG31.84Mild cognitive impairment of uncertain or unknown etiology

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Amnestic mild cognitive disorder
  • Mild neurocognitive disorder
  • Neurocognitive disorder

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G31.84: its own notes plus those printed at G31 and Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Mild cognitive disorder NOS
  • Mild neurocognitive disorder of uncertain or unknown etiology

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • 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)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes
From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

On G31.84 itself
  • 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)
From G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G31.84, its category, or a range that includes it.

Excludes1 3

These codes carry an Excludes1 note naming G31.84: they are not reported together with it, unless the two conditions are unrelated.

  • F06.7 Mild neurocognitive disorder due to known physiological condition
    mild cognitive impairment due to unknown or unspecified etiology (G31.84)
  • F07.0 Personality change due to known physiological condition
    mild cognitive impairment (G31.84)
  • R41 Other symptoms and signs involving cognitive functions and awareness
    mild cognitive impairment of uncertain or unknown etiology (G31.84)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS011
Neurocognitive disorders
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Mild Cognitive Impairment

Some forgetfulness can be a normal part of aging. However, some people have more memory problems than other people their age. This condition is called mild cognitive impairment, or MCI. People with MCI can take care of themselves and do their normal activities.

The full article covers:

  • What is Mild Cognitive Impairment?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert G31.84 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
331.83 Mild cognitive impairemt
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2022No changes
FY 2023RevisedCode revised
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G31.84Overview

What is the ICD-10 code for mild cognitive impairment of uncertain or unknown etiology?

The ICD-10-CM code for mild cognitive impairment of uncertain or unknown etiology is G31.84 (sometimes written as G3184). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G31.84 (Other specified degenerative diseases of nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report mild cognitive impairment of uncertain or unknown etiology on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G31.84 group to?

When mild cognitive impairment of uncertain or unknown etiology is the principal diagnosis on an inpatient stay, it groups to MS-DRG 57, 56, with relative weights from 1.2835 to 2.2649 depending on complications. Higher weights mean higher Medicare reimbursement.

Can G31.84 be reported with R41.81?

Not as a rule. The Excludes1 note on G31.84 lists "age related cognitive decline (R41.81)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

Does G31.84 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: 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 listed in the Instructional Notes section. The additional code is reported after G31.84.