2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G90.2 is a billable ICD-10-CM diagnosis code for Horner's syndrome. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). 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.

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

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

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Bernard-Horner syndrome
    • Claude Bernard-Horner syndrome
    • Dystrophy, dystrophia
      • cervical sympathetic
    • Dystrophy, dystrophia
      • sympathetic (reflex)
        • cervical
    • Horner(-Claude Bernard) syndrome
    • Syndrome
      • cervical (root)
        • sympathetic paralysis
    • Syndrome
      • Horner's
    • Syndrome
      • sympathetic
        • cervical paralysis

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G90.2Overview

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, 2025 through September 30, 2026.

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.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.