2027 ICD-10-CM Diagnosis Code G90.2Horner's syndrome

ICD-10-CM Codes›G00–G99›G89-G99›G90

ICD-10-CM G90.2
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G90.2 is a billable ICD-10-CM diagnosis code for Horner's syndrome. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74. Coders also document this condition as acquired Horner syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system pain and pain syndromes.

G90.2 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 75 for payment year 2027.

Code Identity

ICD-10-CM Code
G90.2
Billable Status
Yes — Valid for Submission
Code Describes
Horner's syndrome
Short Description
Horner's syndrome
Same as the full description in the CMS dataset.
Parent Code
G90
Disorders of autonomic nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG89-G99Other disorders of the nervous system
CategoryG90Disorders of autonomic nervous system
This CodeG90.2Horner's syndrome

Medicare Risk Adjustment (HCC)Billing

G90.2 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Other CMS Models
ESRD (V21): HCC 75
ESRD V21 weights: 0.059 dialysis, 0.284–0.323 functioning graft
Part D (RxHCC)
Not mapped
G90.2 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired Horner syndrome
  • Acquired left-sided Horner syndrome
  • Acquired right-sided Horner syndrome
  • Congenital Horner syndrome
  • Horner syndrome

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G90.2: its own notes plus those printed at G90 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.

  • Bernard(-Horner) syndrome
  • Cervical sympathetic dystrophy or paralysis

Excludes1

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

From G90 Disorders of autonomic nervous system applies to 21 codes
  • dysfunction of the autonomic nervous system due to alcohol (G31.2)

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 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)

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

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 NVS019
Nervous system pain and pain syndromes
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Horner Syndrome

    a syndrome associated with defective sympathetic innervation to one side of the face, including the eye. clinical features include miosis; mild blepharoptosis; and hemifacial anhidrosis (decreased sweating)(see hypohidrosis). lesions of the brain stem; cervical spinal cord; first thoracic nerve root; apex of the lung; carotid artery; cavernous sinus; and apex of the orbit may cause this condition. (from miller et al., clinical neuro-ophthalmology, 4th ed, pp500-11)

Patient EducationClinical

Autonomic Nervous System Disorders

Your autonomic nervous system is the part of your nervous system that controls involuntary actions, such as the beating of your heart and the widening or narrowing of your blood vessels. When something goes wrong in this system, it can cause serious problems, including:

Read the full article at MedlinePlus

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

Convert G90.2 to ICD-9-CMHistory

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

ICD-9-CM
337.9 Autonomic nerve dis NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

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

Questions About G90.2Overview

What is the ICD-10 code for Horner's syndrome?

The ICD-10-CM code for Horner's syndrome is G90.2 (sometimes written as G902). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G90.2 (Disorders of autonomic nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Horner's syndrome on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G90.2 group to?

When Horner's syndrome is the principal diagnosis on an inpatient stay, it groups to MS-DRG 74, 73, with relative weights from 1.0172 to 1.5773 depending on complications. Higher weights mean higher Medicare reimbursement.

Can G90.2 be reported with G31.2?

Not as a rule. The Excludes1 note at G90, which applies to G90.2, lists "dysfunction of the autonomic nervous system due to alcohol (G31.2)". 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).

What is the ICD-9 equivalent of G90.2?

Under the General Equivalence Mappings, Horner's syndrome converts to ICD-9-CM 337.9 (autonomic nerve dis NEC). The mapping is approximate, so confirm the match fits the documentation.

Does G90.2 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: G90.2 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 75 (Polyneuropathy).