What is Horner syndrome?

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Last updated: March 19, 2025View editorial policy

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From the Guidelines

Horner syndrome is a neurological condition characterized by a triad of symptoms: miosis (pupil constriction), ptosis (drooping eyelid), and anhidrosis (decreased sweating) on the affected side of the face, as noted in the most recent study 1.

Definition and Causes

Horner syndrome occurs due to disruption of the sympathetic nerve pathway from the brain to the face and eye. The syndrome can be caused by various conditions including stroke, tumors, trauma, or vascular disorders affecting the sympathetic chain.

Diagnosis and Treatment

Diagnosis typically involves clinical examination and sometimes pharmacological testing with eye drops like cocaine or apraclonidine to confirm the sympathetic denervation, as mentioned in 1. Treatment focuses on addressing the underlying cause rather than the symptoms themselves. For instance, if a tumor is causing compression of the sympathetic pathway, surgical removal may be necessary. If a stroke is responsible, standard stroke management protocols would be followed. There is no specific medication to treat Horner syndrome directly.

Prognosis and Importance of Prompt Evaluation

The prognosis depends entirely on the underlying cause, with some cases resolving completely if the primary condition is successfully treated, while others may be permanent, as indicated in 1. Prompt medical evaluation is essential when Horner syndrome is suspected, as it can sometimes signal serious underlying conditions like carotid artery dissection or lung cancer (Pancoast tumor).

Key Points for Examination

The examination should include a complete ophthalmic examination with emphasis on the sensorimotor evaluation, checking for other neuro-ophthalmic signs and symptoms like Horner’s syndrome, cranial nerve palsy, INO, nystagmus, and hearing loss, as outlined in 1. Fundus examination to check for papilledema or optic atrophy and visual field testing may also provide additional information on the etiology.

From the Research

Definition and Characteristics of Horner Syndrome

  • Horner syndrome is a rare neurologic disorder that can arise from severe neurologic and systemic conditions 2
  • It is often asymptomatic but can have distinct, easily identified characteristics seen with an ophthalmic examination 2
  • The syndrome is typically described by the classic triad of blepharoptosis, miosis, and anhydrosis resulting from disruption along the oculosympathetic pathway 3

Causes of Horner Syndrome

  • The causes of Horner syndrome can be diverse, ranging from benign to life-threatening diseases 3
  • Procedures in the neck, chest, skull base, and paraspinal region accounted for most of the identified causes, with cervical carotid dissection being the next most common cause 4
  • Tumors, especially in the chest and neck region, are also a common cause of Horner syndrome 4
  • Iatrogenic cases, such as those resulting from surgical procedures, can also occur 5

Diagnosis and Investigation

  • The diagnosis of Horner syndrome is typically made through clinical examination, but imaging modalities such as MRI and CT scans may be necessary to determine the underlying cause 6
  • Apraclonidine testing can be used for pharmacological confirmation of Horner syndrome 4
  • A thorough understanding of the condition, appropriate treatment, and management modalities is essential for preventing permanent damage or life-threatening complications 2

Clinical Presentation

  • Patients with Horner syndrome may present with periorbital pain, light sensitivity, syncope, dizziness, and transient ischemic attacks 2
  • The syndrome can be congenital or acquired, and in children, it is classified as such 6
  • In some cases, the identification of Horner syndrome can be critical to the discovery of underlying conditions such as carotid dissection or tumor 4

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Acute Painful Horner Syndrome as the First Presenting Sign of Carotid Artery Dissection.

Federal practitioner : for the health care professionals of the VA, DoD, and PHS, 2023

Research

Horner Syndrome: A Practical Approach to Investigation and Management.

Asia-Pacific journal of ophthalmology (Philadelphia, Pa.), 2012

Research

Causes of Horner Syndrome: A Study of 318 Patients.

Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society, 2020

Research

Iatrogenic Horner Syndrome: Etiology, Diagnosis and Outcomes.

The Israel Medical Association journal : IMAJ, 2017

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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