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Horner's syndrome

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Synonym: Bernard-Horner syndrome (commonly used in France); oculosympathetic paresis

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What is Horner's syndrome?

This is a rare condition that results from disruption of the sympathetic nerves supplying the eye. There is the triad of:

  • Partial ptosis (upper eyelid drooping).

  • Miosis (pupillary constriction) leading to anisocoria (difference in size of the pupils).

  • Hemifacial anhidrosis (absence of sweating).


  • First-order sympathetic fibres originate in the hypothalamus and descend through the brainstem to level C8-T2 of the spinal cord where they synapse on preganglionic sympathetic nerve fibres.

  • Second-order fibres leave the cord at level T1 and ascend in the sympathetic chain over the apex of the lung to synapse in the superior cervical ganglion at the level of the bifurcation of the common carotid artery (C3-C4).

  • Third-order (postganglionic) fibres pass alongside the internal carotid artery, sending branches to the blood vessels and sweat glands of the face, and pass via the cavernous sinus to enter the eye via the superior orbital fissure. They pass via the long ciliary nerves to supply the iris dilator and Müller's muscle.

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Horner's syndrome is an uncommon condition. with a frequency of 1 in 6,000. It has no predeliction for age, sex or race.

Horner's syndrome symptoms

May be asymptomatic.


  • Inability to open eye fully on the affected side.

  • Loss of sweating on the affected side.

  • Facial flushing (if preganglionic lesion).

  • Orbital pain/headache (if postganglionic lesion).

  • There may be other symptoms depending on the underlying cause (see 'Aetiology', below) - eg, head, neck or facial pain on the affected side if associated with carotid artery dissection.


Constricted pupil on the affected side, more apparent in a darkened room:

  • Shine a torch in the eye to make the pupil constrict.

  • Remove the torch and watch the pupil dilate.

  • Do the same on the other side and compare the response.

  • The affected pupil lags behind the other in dilation as it lacks sympathetic tone but the test may need to be repeated several times to detect it55 .

Horner's syndrome

Horner's syndrome

By Waster, CC BY 2.5, via Wikimedia Commons

Ipsilateral dry skin on the face due to loss of sweating:

  • Take both index fingers and place then together in the middle of the forehead. Then run them laterally over the forehead to just lateral to the eyebrows.

  • On the affected side there may be more friction as the skin is drier because there is no sweating on that side.

  • A lesion in the common carotid artery area causes loss of sweating that involves the entire side of the face.

  • Lesions distal to the carotid bifurcation produce lack of sweating on the medial aspect of the forehead and the side of the nose.

  • Ipsilateral partial ptosis (drooping of the upper eyelid) with possible paradoxical contralateral eyelid retraction.

  • There may be apparent mild enophthalmos due to the sagging lid.

  • There is increased amplitude of accommodation.

  • Heterochromia irides may occur with congenital Horner's syndrome6 . The iris on the affected side remains blue whilst the other changes to brown. Pigmentation of the iris is under sympathetic control and is usually complete by the age of 2 years.

  • Examine for the presence of lymphadenopathy (see table, below).

  • Other signs depend on underlying cause (see table, below).

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Horner's syndrome causes (Aetiology)78

Central (first-order) nerve lesions

Preganglionic (second-order) nerve lesions

Postganglionic (third-order) nerve lesions

Cerebrovascular accidents.

Apical lung tumours (eg, Pancoast's tumour).

Cluster headaches or migraine.

Multiple sclerosis.

Lymphadenopathy (lymphoma, leukaemia, tuberculosis, mediastinal tumours).

Herpes zoster infection.

Pituitary or basal skull tumours.

Lower brachial plexus trauma or cervical rib.

Internal carotid artery dissection, may be traumatic.910

Basal meningitis (eg, syphilis).

Aneurysms of the aorta, subclavian or common carotid arteries.

Raeder's syndrome (paratrigeminal syndrome).

Neck trauma (eg, cervical vertebral dislocation or dissection of the vertebral artery).

Trauma or surgical injury (neck or chest).11

Carotid-cavernous fistula.



Temporal arteritis12

Arnold-Chiari malformation.

Mandibular dental abscess.

Spinal cord tumours.

  • Horner's syndrome associated with pain always needs investigation. If there is arm, shoulder or hand pain think of Pancoast's syndrome. If pain is in the face or neck, think of carotid dissection. Pain and transient visual loss may be due to carotid dissection3 .

  • In children, unless there is a known aetiology such as birth trauma, acquired Horner's syndrome requires thorough investigation; there is frequently a serious underlying cause, including neuroblastoma, trauma, rhabdomyosarcoma and brainstem vascular malformation13 .

  • A rare congenital form of Horner's syndrome is described6 . It may present as an autosomal dominant condition or as a spontaneous mutation.

  • Preganglionic lesions are less common but are more likely to be malignant.

Differential diagnosis


Investigations will be guided by suspected aetiology. For example14 :

  • CXR may show an apical carcinoma of the lung.

  • CT/MRI may be useful to identify a cerebrovascular accident.

  • CT angiography/carotid ultrasound may demonstrate dissection of the carotid artery.

Pharmacological testing

Pharmacological testing can help to confirm the diagnosis and identify if the lesion is preganglionic or postganglionic14 :

  • Cocaine eye drops will normally cause dilatation of the pupil but there is no response in Horner's syndrome. Cocaine inhibits the reuptake of noradrenaline (norepinephrine) but this requires an intact sympathetic system. Cocaine drops can confirm the diagnosis but do not localise the lesion. Their use was universal in the past but has been superseded by the newer agents below.

  • Apraclonidine is an alternative to cocaine. It has little effect on a normal pupil but causes dilation of a pupil affected by Horner's syndrome.

  • Hydroxyamfetamine 1% drops can also be instilled to both eyes but it is necessary to wait at least 48 hours after performing the cocaine test. The drops stimulate the release of noradrenaline (norepinephrine) from postganglionic nerves and cause dilation of the pupil (similar to that in the unaffected eye) if these nerves are intact. Hence, a first- or second-order nerve lesion will result in dilation but no dilation occurs with third-order (postganglionic) lesions.

Horner's syndrome treatment and management

Horner's syndrome is a physical sign. Management involves diagnosis of the underlying condition and treatment as appropriate.


Johann Friedrich Horner (1831-1886) was a Swiss ophthalmologist. He was made Professor of Ophthalmology in Zurich in 1873. He described the syndrome that bears his name in 1869 although it was reported by others in earlier animal and human studies15 . In France it is called Bernard-Horner syndrome, adding the name of Claude Bernard. Horner's other achievements included the observation that red-green colour blindness is transferred to males through the female line.

Further reading and references

  1. Bazari F, Hind M, Ong YE; Horner's syndrome - not to be sneezed at. Lancet. 2010 Feb 27;375(9716):776.
  2. Khan Z, Bollu PC; Horner Syndrome
  3. Chopra NR, Jones DA, Gadi N, et al; Sudden onset of pain in the eye and blurring of vision. BMJ. 2009 Jan 21;338:a3111. doi: 10.1136/bmj.a3111.
  4. Horner's Syndrome; Atlas of Ophthalmology, 2021
  5. Crippa SV, Borruat FX, Kawasaki A; Pupillary dilation lag is intermittently present in patients with a stable oculosympathetic defect (Horner syndrome). Am J Ophthalmol. 2007 Apr;143(4):712-5. Epub 2006 Dec 8.
  6. Horner Syndrome, Congenital; Online Mendelian Inheritance in Man (OMIM)
  7. How and When Should I Work-Up Horner Syndrome?; Ocular Surgery News, 2020
  8. Bucci T, Califano L; Bernard-Horner's syndrome: unusual complication after neck dissection. J Oral Maxillofac Surg. 2008 Apr;66(4):833.
  9. Costopoulos C, Patel RS, Mistry CD; Painful Horner's syndrome. Emerg Med J. 2008 May;25(5):295.
  10. Makhlouf F, Scolan V, Detante O, et al; Post-traumatic dissection of the internal carotid artery associated with ipsilateral facial nerve paralysis: diagnostic and forensic issues. J Forensic Leg Med. 2013 Oct;20(7):867-9. doi: 10.1016/j.jflm.2013.06.018. Epub 2013 Aug 13.
  11. Allen AY, Meyer DR; Neck procedures resulting in Horner syndrome. Ophthal Plast Reconstr Surg. 2009 Jan-Feb;25(1):16-8.
  12. Pupillary abnormalities; Atlas of Ophthalmology
  13. Mahoney NR, Liu GT, Menacker SJ, et al; Pediatric horner syndrome: etiologies and roles of imaging and urine studies to detect neuroblastoma and other responsible mass lesions. Am J Ophthalmol. 2006 Oct;142(4):651-9.
  14. Davagnanam I, Fraser CL, Miszkiel K, et al; Adult Horner's syndrome: a combined clinical, pharmacological, and imaging algorithm. Eye (Lond). 2013 Mar;27(3):291-8. doi: 10.1038/eye.2012.281. Epub 2013 Feb 1.
  15. Abbas A, Manjila S, Singh M, et al; Johann Friedrich Horner and the Repeated Discovery of Oculosympathoparesis: Whose Syndrome Is It? Neurosurgery. 2015 Sep;77(3):486-91; discussion 491. doi: 10.1227/NEU.0000000000000832.

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The information on this page is written and peer reviewed by qualified clinicians.

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