U.S. flag

An official website of the United States government

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

Cover of StatPearls

StatPearls [Internet].

Show details

Horner Syndrome

; .

Author Information and Affiliations

Last Update: April 10, 2023.

Continuing Education Activity

Horner syndrome is a rare condition classically presenting with partial ptosis (drooping or falling of the upper eyelid), miosis (constricted pupil), and facial anhidrosis (absence of sweating) due to a disruption in the sympathetic nerve supply. It is primarily acquired following damage to the sympathetic nerve supply, but rare cases of congenital forms have been seen. Treatment is centered around the identification and appropriate management of the underlying cause. This activity reviews the evaluation and management of Horner syndrome and highlights the role of the interprofessional team in the management of affected patients.


  • Identify the etiology of Horner syndrome.
  • Describe the presentation of a patient with Horner syndrome.
  • Outline the management options available for patients with Horner syndrome.
  • Summarize interprofessional team strategies for improving care coordination and communication to advance the diagnosis and treatment of Horner syndrome and improve patient outcomes.
Access free multiple choice questions on this topic.


Horner syndrome is a rare condition classically presenting with partial ptosis (drooping or falling of upper eyelid), miosis (constricted pupil), and facial anhidrosis (loss of sweating) due to a disruption in the sympathetic nerve supply. It is primarily acquired following damage to the sympathetic nerve supply, but rare cases of congenital forms have been seen. Therefore, treatment is centered around identifying and appropriate management of the underlying secondary cause.

The syndrome has several names, such as Bernard-Horner syndrome (French-speaking countries), Horner syndrome (English speaking countries), oculosympathetic palsy, and Von Passow syndrome (Horner syndrome in association with iris heterochromia).

The syndrome was first described by Francois Pourfour du Petit in 1727 when considering results from an animal experiment involving resection of intercostal nerves and subsequent changes seen in the ipsilateral eye and face.[1] It was outlined more thoroughly by the French physiologist Claude Bernard in 1852, followed by several physicians who offered different interpretations.

The condition was formally described and later named after Swiss ophthalmologist Johann Friedrich Horner in 1869.[2][3][4][5]


Understanding the sympathetic innervation of the eye is vital to understanding the features of this syndrome. The nerve supply is constituted by three different neurons, starting from the posterolateral hypothalamus and ending as the long ciliary nerves to supply the iris dilator and superior tarsal muscles (Muller muscle).[6]

The first-order neurons originate from the hypothalamus and descend through the midbrain and pons uncrossed, terminating at the C8-T2 level of the spinal cord in the intermediolateral cell columns (ciliospinal center of Budge). Second-order preganglionic neurons exit at the T1 level of the spinal cord to enter the cervical sympathetic chain, where the fibers ascend to synapse in the superior cervical ganglion at the C3-C4 level.[7]

Third-order, postganglionic fibers branch off into the sudomotor and vasomotor fibers, which follow the external carotid artery and innervate the sweat glands and blood vessels of the face. The remaining fibers ascend along the internal carotid artery in the carotid plexus to eventually enter the cavernous sinus, where they join the abducens nerve (CN VI). The fibers then exit the cavernous sinus to enter the orbit via the superior orbital fissure and the ophthalmic branch (V1) of the trigeminal nerve (CN V) as the long ciliary nerves.


Horner syndrome is primarily an acquired condition secondary to systemic/local diseases or iatrogenic causes but maybe congenital and purely hereditary in some rare cases.[8][9] Sympathetic fibers have an extensive course and can be interrupted during extracranial, intracranial, or intra-orbital traversal.[10][11][12] The sympathetic fibers may be interrupted centrally, between the hypothalamus and the exit point of fibers from the spinal cord (C8 to T2), or the discontinuation could be peripheral, in the cervical sympathetic chain, at the level of superior cervical ganglion, or along the course of the carotid artery.[10] Preganglionic Horner syndrome can be an ominous sign due to its association with pulmonary malignancies. Overall, the causes of Horner syndrome can be divided according to the anatomical location of disruption.

First-order neurons are mostly affected by intracranial conditions and include the following:[13][14][15]

  • Cerebral vascular accidents (CVA)
  • Multiple sclerosis
  • Arnold-Chiari malformation
  • Encephalitis
  • Meningitis
  • Lateral medullary syndrome 
  • Syringomyelia
  • Intracranial tumors (pituitary or basal skull)
  • Spinal trauma above the T2-T3 level
  • Spinal cord tumors

Second-order neurons traverse the thoracic region and are affected by the following:

  • Malignancies involving the apex of the lungs (Pancoast tumor)
  • Cervical rib (tractional injury)
  • Lesions of the subclavian artery (an aneurysm)
  • Mediastinal lymphadenopathy
  • Trauma to brachial plexus[11]
  • Neuroblastoma of the paravertebral sympathetic chain[15]
  • A dental abscess involving the mandibular region
  • Iatrogenic (including thyroidectomy, radical neck dissection, tonsillectomy, coronary artery bypass grafting, or carotid angiography)[12][16][13][17][13]

Third-order neurons are in close proximity to the internal carotid artery and cavernous sinus and are affected by the following:

  • Carotid cavernous fistula
  • Internal carotid artery dissection or an aneurysm[18]
  • Cluster headaches or migraines
  • Raeder paratrigeminal syndrome (unilateral facial pain, headache, and Horner syndrome)
  • Herpes zoster infection
  • Temporal arteritis


Horner syndrome is uncommon, occurring with a frequency of approximately 1 per 6,000. It may occur at any age or with any ethnic group.[15][19]


As previously described, Horner syndrome is a consequence of sympathetic disruption. The symptomology depends on the location of the lesion, and severity depends on the degree of denervation.[9]

Superior tarsal muscle helps raise the upper eyelid and has a sympathetic nerve supply. Denervation of this muscle causes ptosis, which is milder than oculomotor (CN III) palsy which supplies the levator palpebrae superioris. The superior tarsal muscle is responsible for keeping the upper eyelid in a raised position after levator palpebrae superioris raises it. This explains the partial ptosis seen in Horner syndrome. The lower eyelid may be slightly elevated owing to denervation of the lower lid muscle, which is analogous to the superior tarsal muscle.[20]

The sympathetic nervous supply is responsible for pupil dilationupil (mydriasis). When disrupted, parasympathetic supply is uninhibited, and constriction of the pupil (miosis) ensues. The reaction of the pupils to light and accommodation is normal as those systems do not depend on sympathetic nerve supply.[21]

Ipsilateral anhidrosis, another classic presentation, depends on the level of interruption of the sympathetic supply. Anhidrosis with first-order neuron lesions affects the ipsilateral side of the body as the sympathetic supply from its central origin.[22] The ipsilateral face is involved in lesions involving the second-order neurons. Postganglionic third-order neuron lesions after the vasomotor and sudomotor fibers have branched off show very limited involvement of the face (area adjacent to the ipsilateral brow).

Iris heterochromia (relevant deficiency of pigment in the iris on the affected side) is seen in children younger than 2 years and is the congenital form of Horner syndrome.[9]

History and Physical

Localization of the lesion in Horner syndrome is crucial in subsequent management. A detailed history and physical examination are, therefore, of vital importance. When evaluating, the following points need to be considered:

  • Balance, hearing, sensory, and swallowing problems can point towards a more central process involving the first-order neurons.
  • Prior history of trauma or surgical intervention involving the head, face, neck, shoulder, or back points towards the involvement of second-order neurons.[17]
  • A detailed past medical and medication history to rule out the use of a miotic or mydriatic agent.
  • A headache, double vision, facial numbness, or pain indicate third-order neuron involvement.
  • The presence of anhidrosis and its location can help in the localization.
  • A detailed history of a headache if present.
  • Longstanding symptoms point towards a more benign underlying cause versus recently progressive symptoms such as weight loss, hemoptysis, low-grade fever, and lymphadenopathy.
  • Facial flushing suggests a preganglionic lesion.[23]
  • Facial or orbital pain in combination with miosis and ptosis should point towards Raeder paratrigeminal syndrome.[24]
  • History of skin lesions or previously diagnosed herpes zoster infection.
  • Severity and location of the pain.

A detailed examination of the eyes is warranted and should include the following:

  • Reactivity of the pupils to light and accommodation
  • Measurement of pupillary diameter in dim and bright light
  • Examination of the upper eyelid for ptosis and fatigability
  • Evaluation of extraocular movements
  • Vision, including color vision and visual fields
  • Slit-lamp examination for structural details 
  • Evaluation of the presence of nystagmus

A detailed exam can reveal a round and constricted pupil. The affected pupil exhibits dilation lag (dilates more slowly), and the unequal pupils are appreciated more in darkness compared to light. In addition, the ciliospinal reflex may be absent.

Furthermore, partial ptosis, iris heterochromia, apparent enophthalmos, contralateral eyelid retraction, injected conjunctivae, and no change or a transient decrease in intraocular pressure may be seen.[25][18][17]

It is important to perform a detailed systemic examination, paying specific attention to neurological, pulmonary, and cardiovascular systems and considering various differentials discussed later.



  • The initial workup should include a complete blood count (CBC), erythrocyte sedimentation rate (ESR), and serum chemistry panel.
  • Urine or blood cultures may be ordered if an infectious agent is suspected.
  • Testing for suspected neurosyphilis, HIV, thyroid function, vitamin B-12, and folate levels may be ordered if indicated following detailed history and examination.
  • Urine testing for elevated metabolic catecholamine by-products is important in the pediatric population with suspected neuroblastoma.
  • Purified protein derivative (PPD) is warranted in suspected tuberculosis.


  • A chest X-ray followed by computed tomography (CT) scan must be ordered in patients when pulmonary malignancy is suspected.
  • Head CT and magnetic resonance imaging (MRI) are advised in cases of possible stroke.
  • MRI is warranted and preferred over ultrasonography when carotid artery dissection is a possibility (painful Horner syndrome).[26]

Pharmacological Testing

This is the most helpful testing modality for diagnostic localization.[27]

Topical Cocaine Test: Cocaine acts as an indirect sympathomimetic inhibiting the reuptake of norepinephrine from the synaptic cleft. Cocaine solution (ranging from 2% to 10%) is instilled into both eyes. Both eyes are evaluated after at least 30 or more minutes for an optimal response. Denervation in the affected eye causes it to dilate poorly compared to the normal one. Anisocoria of 0.8 mm or more is considered diagnostic. However, the test does not help in identifying the level of the lesion.

The test has other disadvantages such as comparatively high prices of the compound, time-consuming, test yielding ambiguous results, and the metabolites of cocaine can be detected in urine.[28]

Topical Hydroxyamphetamine Test: This test is particularly helpful in the localization of the lesion. Hydroxyamphetamine stimulates the release of stored norepinephrine from the postganglionic terminals into the synapse. Postganglionic third-order lesions can be differentiated from presynaptic second-order or first-order ones.

Two drops of 1% hydroxyamphetamine solution are instilled into both eyes. As a result, the affected eye (third-order lesion) will not dilate as well as the normal eye. While in the case of intact postganglionic fibers (first and second-order lesions), the affected pupil dilates to an equal or greater extent.

Disadvantages involving this test include it not being able to be performed on the same day as the cocaine test and false-negative results.[28] 

Topical Apraclonidine Test: This test is considered the test of choice due to its good sensitivity and overall practicality. Apraclonidine acts as a weak alpha1-agonist and strong alpha2-agonist. It is categorized as an ocular hypotensive agent. The upregulation of alpha1-receptors in Horner syndrome translates into an exaggerated response of the iris dilators (denervation supersensitivity) to an agonist agent like apraclonidine.[29]

A 0.5-1% solution is instilled in both eyes. The affected eye will show mydriasis, while the normal eye is predominantly insensitive. Consequent instillation of the solution results in an evident reversal of anisocoria (the affected pupil dilates and the normal pupil constricts). This is because of the stronger alpha 2 agonist activity compared to the weaker alpha 1 agonist activity of apraclonidine.

Some disadvantages of this form of testing include false-negative results in acute cases, systemic side effects in the pediatric population, inability to localize the lesion, and relatively long half-life of the drug.

Other agents have been proposed but fall short of clinical relevance due to several reasons, such as:

  • Pholedrine, an N-methyl derivative of hydroxyamphetamine, is roughly half as potent as hydroxyamphetamine and has shown comparable results, but due to limited availability, it has been restricted.
  • Adrenaline, a direct-acting sympathomimetic, also has been proposed but has poor penetration through the cornea, and sensitivity to the drug is variable.
  • Phenylephrine, a selective alpha1 agonist, also has been proposed but suffers from poor penetration through the cornea and varying results, depending on the degree of denervation.[30]

Treatment / Management

Treatment options are based on the diagnosis and management of the underlying cause. Timely diagnosis is of critical importance, followed by referral to an appropriate specialist. Healthcare professionals are advised to incorporate the importance of eye examinations into their acumen.

Whether surgical intervention is indicated and what type is appropriate largely depends on the cause of the disease. Surgical treatment options include the following:

  • Neurosurgical attention for aneurysm-related Horner syndrome 
  • Vascular surgical care for causes such as carotid artery dissection or aneurysm

Differential Diagnosis

As previously described, pain accompanied by Horner syndrome points towards a more insidious underlying cause and should be evaluated thoroughly. Systemic symptoms such as weight loss and progressive fatigue can indicate an underlying malignancy. Furthermore, Horner syndrome can be an early manifestation of neuroblastoma in the pediatric population. 

Carotid artery dissection can present with a unilateral headache and facial or neck pain. If suspected, urgent appropriate workup and treatment are warranted.

Raeder paratrigeminal syndrome also can present with headaches but is accompanied by trigeminal nerve (CN V) impairment.

Anisocoria and/or ptosis can be due to myriad diseases and conditions such as Holmes-Adie syndrome, neurosyphilis (Argyll Robertson pupil), third nerve palsy, or optic neuritis.


The long-term prognosis of idiopathic Horner syndrome appears to be benign. Clinically, patients do not generally become worse, and in fact, half of the patients no longer experience anisocoria. Almost a third of patients with ptosis notice spontaneous improvement or complete resolution in a mean duration of 7.9 years after Horner syndrome is diagnosed. In unilateral cases, the oculo-sympathetic defect does not progress to become bilateral. It is possible that new medical disorders later develop between 3 and 20 years after the diagnosis of Horner syndrome; none are usually related to Horner syndrome.[31]


Horner syndrome is almost always secondary to an underlying cause, such as tumor, trauma, infection, etc, and is rarely idiopathic. The complications that occur as a result of Horner syndrome are essentially related to the cause of Horner syndrome. For instance, if Horner syndrome is secondary to multiple sclerosis, it could lead to muscle stiffness or spasms, impaired bladder, bowel, or sexual function; and seizures. Similarly, Horner syndrome-related eye problems can lead to problems with vision that could be temporary or permanent. Visual involvement can lead to partial or complete blindness.


For the appropriate management of Horner syndrome and the underlying cause, the following consultations may be needed:

  • Pulmonology
  • Neurology
  • Neurosurgery
  • Interventional radiology
  • Oncology
  • Neuro-ophthalmology

Deterrence and Patient Education

Patients should be educated about the possible presentations of Horner syndrome. Parents of babies born with congenital Horner syndrome should be aware of the management options and follow-ups. Patients of Horner syndrome should be informed that it will not damage the eye or cause vision loss, but it could be a sign of damage to structures along the nerve. It is essential to explore where the damage is and its cause because sometimes the underlying cause can be severe. For example, ptosis predisposes eyes to overexposure which makes them red. In addition, patients may complain of a gritty sensation and are prone to infection. Artificial tears and ointment are often enough; however, surgery may be needed in severe or more complicated cases.

Enhancing Healthcare Team Outcomes

There are many causes of Horner syndrome and thus the condition is best managed by an interprofessional team that includes nurse practitioners. The key is to determine the location of the eye defect. Thus, it is important to perform a detailed systemic examination, paying specific attention to neurological, pulmonary, and cardiovascular systems and considering various differentials discussed later.

The outcomes depend on the cause.

Review Questions



Horner syndrome Image courtesy S Bhimji MD


van der Wiel HL. Johann Friedrich Horner (1831-1886). J Neurol. 2002 May;249(5):636-7. [PubMed: 12021960]
Thompson HS. Johann Friedrich Horner (1831-1886). Am J Ophthalmol. 1986 Dec 15;102(6):792-5. [PubMed: 3538884]
Johann Friedrich Horner, (1831-1886) "a form of ptosis". JAMA. 1969 Jun 09;208(10):1899-900. [PubMed: 4890333]
Mitchell SW, Morehouse GR, Keen WW. Gunshot wounds and other injuries of nerves. 1864. Clin Orthop Relat Res. 2007 May;458:35-9. [PubMed: 17473596]
DURHAM DG. Congenital hereditary Horner's syndrome. AMA Arch Ophthalmol. 1958 Nov;60(5):939-40. [PubMed: 13582337]
Amonoo-Kuofi HS. Horner's syndrome revisited: with an update of the central pathway. Clin Anat. 1999;12(5):345-61. [PubMed: 10462732]
Lee JH, Lee HK, Lee DH, Choi CG, Kim SJ, Suh DC. Neuroimaging strategies for three types of Horner syndrome with emphasis on anatomic location. AJR Am J Roentgenol. 2007 Jan;188(1):W74-81. [PubMed: 17179330]
Biousse V, Touboul PJ, D'Anglejan-Chatillon J, Lévy C, Schaison M, Bousser MG. Ophthalmologic manifestations of internal carotid artery dissection. Am J Ophthalmol. 1998 Oct;126(4):565-77. [PubMed: 9780102]
Reede DL, Garcon E, Smoker WR, Kardon R. Horner's syndrome: clinical and radiographic evaluation. Neuroimaging Clin N Am. 2008 May;18(2):369-85, xi. [PubMed: 18466837]
Lyrer PA, Brandt T, Metso TM, Metso AJ, Kloss M, Debette S, Leys D, Caso V, Pezzini A, Bonati LH, Thijs V, Bersano A, Touzé E, Gensicke H, Martin JJ, Lichy C, Tatlisumak T, Engelter ST, Grond-Ginsbach C., Cervical Artery Dissection and Ischemic Stroke Patients (CADISP) Study Group. Clinical import of Horner syndrome in internal carotid and vertebral artery dissection. Neurology. 2014 May 06;82(18):1653-9. [PubMed: 24727317]
Jadon A. Horner's syndrome and weakness of upper limb after epidural anaesthesia for caesarean section. Indian J Anaesth. 2014 Jul;58(4):464-6. [PMC free article: PMC4155296] [PubMed: 25197119]
Ying X, Dandan G, Bin C. Postoperative Horner's syndrome after video-assisted thyroidectomy: a report of two cases. World J Surg Oncol. 2013 Dec 30;11:315. [PMC free article: PMC4029459] [PubMed: 24378178]
Foss-Skiftesvik J, Hougaard MG, Larsen VA, Hansen K. Clinical Reasoning: Partial Horner syndrome and upper right limb symptoms following chiropractic manipulation. Neurology. 2015 May 26;84(21):e175-80. [PubMed: 26009566]
Sandoval MA, Cabungcal AC. Horner syndrome after radical neck surgery for anaplastic thyroid carcinoma. BMJ Case Rep. 2015 Apr 09;2015 [PMC free article: PMC4401968] [PubMed: 25858945]
Smith SJ, Diehl N, Leavitt JA, Mohney BG. Incidence of pediatric Horner syndrome and the risk of neuroblastoma: a population-based study. Arch Ophthalmol. 2010 Mar;128(3):324-9. [PMC free article: PMC3743544] [PubMed: 20212203]
Kucur C, Ozbay I, Oghan F, Yildirim N, Zeybek Sivas Z, Canbaz Kabay S. A Rare Complication of Radiofrequency Tonsil Ablation: Horner Syndrome. Case Rep Otolaryngol. 2015;2015:570520. [PMC free article: PMC4439494] [PubMed: 26064747]
Allen AY, Meyer DR. Neck procedures resulting in Horner syndrome. Ophthalmic Plast Reconstr Surg. 2009 Jan-Feb;25(1):16-8. [PubMed: 19273916]
Pirouzian A, Holz HA, Ip KC, Sudesh R. Acquired infantile Horner syndrome and spontaneous internal carotid artery dissection: a case report and review of literature. J AAPOS. 2010 Apr;14(2):172-4. [PubMed: 20451860]
Guglielmi V, Visser J, Arnold M, Sarikaya H, van den Berg R, Nederkoorn PJ, Leys D, Calvet D, Kloss M, Pezzini A, Tatlisumak T, Schilling S, Debette S, Coutinho JM. Triple and quadruple cervical artery dissections: a systematic review of individual patient data. J Neurol. 2019 Jun;266(6):1383-1388. [PMC free article: PMC6517349] [PubMed: 30904955]
Kong YX, Wright G, Pesudovs K, O'Day J, Wainer Z, Weisinger HS. Horner syndrome. Clin Exp Optom. 2007 Sep;90(5):336-44. [PubMed: 17697179]
Walker L, French S. Horner's Syndrome: A Case Report and Review of the Pathophysiology and Clinical Features. West Indian Med J. 2014 Jun;63(3):278-80. [PMC free article: PMC4663911] [PubMed: 25314289]
Ofri A, Malka V, Lodh S. Horner's syndrome in traumatic first rib fracture without carotid injury; review of anatomy and pathophysiology. Trauma Case Rep. 2017 Apr;8:1-4. [PMC free article: PMC5883210] [PubMed: 29644305]
Morrison DA, Bibby K, Woodruff G. The "harlequin" sign and congenital Horner's syndrome. J Neurol Neurosurg Psychiatry. 1997 Jun;62(6):626-8. [PMC free article: PMC1074149] [PubMed: 9219751]
Cho TT, Da Costa JL. Raeder's paratrigeminal syndrome. Singapore Med J. 1968 Jun;9(2):92-7. [PubMed: 4300458]
González-Aguado R, Morales-Angulo C, Obeso-Agüera S, Longarela-Herrero Y, García-Zornoza R, Acle Cervera L. Horner's syndrome after neck surgery. Acta Otorrinolaringol Esp. 2012 Jul-Aug;63(4):299-302. [PubMed: 22502736]
Almog Y, Gepstein R, Kesler A. Diagnostic value of imaging in horner syndrome in adults. J Neuroophthalmol. 2010 Mar;30(1):7-11. [PubMed: 20182199]
Smit DP. Pharmacologic testing in Horner's syndrome - a new paradigm. S Afr Med J. 2010 Nov 09;100(11):738-40. [PubMed: 21081027]
Mughal M, Longmuir R. Current pharmacologic testing for Horner syndrome. Curr Neurol Neurosci Rep. 2009 Sep;9(5):384-9. [PubMed: 19664368]
Bremner F. Apraclonidine Is Better Than Cocaine for Detection of Horner Syndrome. Front Neurol. 2019;10:55. [PMC free article: PMC6371044] [PubMed: 30804875]
Koc F, Kavuncu S, Kansu T, Acaroglu G, Firat E. The sensitivity and specificity of 0.5% apraclonidine in the diagnosis of oculosympathetic paresis. Br J Ophthalmol. 2005 Nov;89(11):1442-4. [PMC free article: PMC1772929] [PubMed: 16234449]
Bellégo C, Borruat FX, Kawasaki A. Long-term prognosis of patients with idiopathic Horner syndrome. J Neurol. 2022 May;269(5):2781-2783. [PubMed: 34839389]

Disclosure: Zalan Khan declares no relevant financial relationships with ineligible companies.

Disclosure: Pradeep Bollu declares no relevant financial relationships with ineligible companies.

Copyright © 2024, StatPearls Publishing LLC.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Bookshelf ID: NBK500000PMID: 29763176


  • PubReader
  • Print View
  • Cite this Page

Related information

  • PMC
    PubMed Central citations
  • PubMed
    Links to PubMed

Similar articles in PubMed

See reviews...See all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...