Horner’s Syndrome: Rare and Possibly Life Threatening Causes – Part 1: Overview

Horner’s Syndrome/Bernard’s Syndrome – What Exactly Is It?

Horner’s Syndrome is a rare syndrome that is based upon findings that are due to an alteration in the sympathetic neuro-pathway. Approximately 60% of  cases studied are from known causes and the other 40% are idiopathic 1.The main and most common characteristics of this syndrome are ptosis of the eyelids and ipsilateral miosis of the pupil. Horner’s Syndrome is of high concern as it could be due to many possible causes, some being serious and possibly life threatening.

Symptoms of Horner’s Syndrome

There are many findings that are seen in Horner’s Syndrome patients. The most common visible signs are ipsilateral miosis, anhidrosis and ptosis of the affected eye:

  • Ptosis is caused by the paralysis of the Muller’s muscle and is typically mild while worsening later in the day. In addition to the upper lid ptosis, there is sometimes an inverse ptosis in the lower eyelid (where the lower lid assumes a higher position). Both ptosis of the upper eyelid and the inverse ptosis of the lower eyelid gives the eye a pseudo-enophthalmic appearance (in which the eyeball seems to recede back into the eye socket but, in reality, it has not).
  • Miosis can best be determined in dim illumination in which the paresis of the iris dilator becomes noticeable. In conjunction with this result, marked anisocoria typically occurs within seconds after the lights are dimmed (dilation lag). The affected pupil falters in dilation due to the reduced innervation to the iris dilator muscle. Since innervation to the iris sphincter is intact, pupil responses to near and light are still intact.
  • Anhidrosis is noted when the patient has ipsilateral loss of sweating on the half of his/her body where the affected eye is. It is noted that the sweating is different between patients with pre-ganglionic and post-ganglionic Horner’s Syndrome. Pre-ganglionic patients tend to have a reduced or absent sweating, while post-ganglionic patients often have normal sweating.

Adding to these 3 main characteristics are other less common findings, which include, but are not limited to 2, 3:

  • Heterochromia is usually noted in children (due to a congenital cause)
  • Change of accommodation, usually an increase in amplitude on affected side
  • Ocular hypotony (lower intraocular pressure)  by at least 5mmHg less than other eye
  • Possibility of difference in extraocular movement
  • Anhidrosis (ipsilateral sweating in the face)
  • Diplopia (double vision)
  • Harlequin (impaired hemi-facial flushing)
  • Ataxia (lack of voluntary coordination or muscle movements)
  • Nystagmus (involuntary eye movement)
  • Lateralized weakness/numbness
  • Hoarseness (difficulty in speaking)
  • Dysphagia (difficulty swallowing)
  • Sensory/motor abnormalities
  • Dysfunction of bowel/bladder movements
  • Erectile dysfunction
  • Pain/weakness in arm or hand

Possible Causes of Horner’s Syndrome

Since Horner’s Syndrome is just a list of findings, there are many possibilities causes. Doctors first have to determine where to look in the body to find what the possible cause is. This decision is made by using multiple tests:

  • Ask about medical history 3:
    • Neck/chest/heart operations that may have injured the sympathetic chain
    • Neck trauma which included wearing a neck collar
    • Examine patient with palpations of neck for masses, thyroid nodules, supraclavicular nodes
  • Topical cocaine: Used to block the reuptake of norepinephrine at the motor endplate and prolongs its action on the effector cell 3. If there is no dilation in the pupil this indicates that the sympathetic pathway is interrupted 3.
    • Topical cocaine has now become difficult to obtain in the US due to its short shelf life and is a controlled substance. The more popular dilation drops are now apraclonidine.
  • Epinephrine: Used as a stimulator of the motor endplate and will dilate a hypersensitive pupil 3.
  • Topical apraclonidine: Used as an alpha adrenergic agonist causing pupillary dilation of the smaller pupil due to denervation supersensitivity. However, the normal pupil is only mildly dilated due to the downregulation of norepinephrine 2.
  • Topical hydroxyamphetamine: Used to release endogenous norepinephrine from the intact adrenergic nerve allowing for pupil dilations 2. This is used to determine between pre-ganglionic (first order neuron) and post-ganglionic (second or third order neurons) defects. A Horner’s Syndrome pupil will not dilate in post-ganglionic patients but will dilate in pre-ganglionic patients.
    • Topical hydroxamphetamine, like cocaine, is no longer used in the US and has been substituted by pholedrine.
  • Pholedrine: Used to produce a forced release of endogenous norepinephrine from the presynaptic vesciles. Unlike hydroxyamphetamine, the pupil will not dilate in postganglionic patients.6

After these tests are preformed, it can be determined what neurons are affected and where in the body the doctor should be testing. Listed below are the different neuron pathways that can be affected and what causes could be of concern:

First Order Neuron (Central Horner’s Syndrome)

  • Pathway: Descends from the hypothalamus and runs down spinal cord 4
  • Causes 3,4
    • Vertebral-basilar insufficiency (Wallenberg Syndrome)
    • Residual signs of transient ischemic episode
    • Severe osteoarthritis of neck indicated by obvious bony spurs
    • Severe whiplash injury
    • Ischemia or hemorrhage in brain
    • Vascular malformations
    • Brain tumor
    • Chiara malformations
    • Basal meningitis
    • Demyelinating disease
    • Cervical spine injury
    • Syrinx
    • Cervical spinal cord tumor
    • Vascular malformations
  • Signs: neurological signs appear to be on opposite sides of the nervous system 3

Second Order Neuron (Pre-Ganglionic Horner’s Syndrome)

  • Pathway:  Originates from ciliospinal center (C8 – T2) 4 and ascends down the cervical sympathetic chain through the brachial plexus. Afterwards, the pathway enters the pulmonary apex and synapses in the superior cervical ganglion 2
  • Causes 3,4
    • Apical lung cancer (pancoast tumour)
    • Mediastinal tumour
    • Phrenic nerve syndrome
    • Trauma to spinal cord/chest/neck
    • Syrinx
    • Herniated disk
    • Cervical rib displacement
    • Aneurysm or dissection of aorta/subclavian artery/carotid artery
    • Spinal cord/thyroid/mediastinal tumours
    • Neuroblastoma
    • Lymphadenopathy (abnormal lymph nodes size)
    • Mandibular tooth abscess
    • Middle ear lesions
    • Iatrogenic causes (illness caused by medical examination/procedure):
      • lumbar epidural anesthesia, chest tube placement, central line placement in internal jugular vein, neck/chest/heart surgery, assisted delivery with forceps

Third Order Neuron (Postganglionic Horner’s Syndrome)

  • Pathway:  originates from superior cervical ganglion 4 and enters the cranium in adventitia of the internal carotid artery into the cavernous sinus. The oculosympathetic fibers then exit the carotid artery into the trigeminal ganglion in the sixth cranial nerve which then joins the division of the trigeminal nerve 2
  • Causes 3,4
    • Raeder’s Paratrigeminal Syndrome
    • Cluster headaches
    • Migraines
    • Idiopathic hemifacial hyperhidrosis
    • Carotid artery dissection/aneurysm/thrombosis
    • Venous sinus thrombosis (blood clot)
    • Carotid-cavernous fistula (abnormal connection between tissue) 
    • Jugular venous ectasia (dilation/distention of hollow organ)
    • Trauma
    • Orbital apex and skull base tumours
    • Cavernous sinus tumours
    • Herpes zoster/shingles
    • Lyme disease
    • Granulomatosis with polyangititis (blood vessel disease)
    • Temporal arteritis
  • Signs 3,4: postsympathectomy facial hyperhidrosis and hemifacial anhidrosi (forms of abnormal sweating)

Interested in learning more about Horner’s Syndrome from a patient’s perspective? Stay tuned for the next article in this series, coming soon!

  1. Maloney WF, Younge BR, Moyer NJ. Evaluation of the causes and accuracy of pharmalogica localization in Horner’s syndrome. American Journal of Ophthalmology. 1980; 90: 394-402. Available at American Journal of Ophthalmology. Accessed February 9, 2014
  2. Horner’s syndrome. In EyeWiki [database online]. http://eyewiki.aao.org/Horner’s_syndrome. Updated January 22, 2013. Accessed February 9, 2014.
  3. Horner syndrome. In Orbis [database online]. http://telemedicine.orbis.org/bins/volume_page.asp?cid=1-2630-2644-2656. Updated January 22, 2013. Accessed February 9, 2014.
  4. Horner syndrome evaluation. In DynaMed [database online]. EBSCO Information Services. http://eds.a.ebscohost.com.login.ezproxy.library.ualberta.ca/eds/detail?sid=544f801e-e663-43bb-b845-884485ad4241%40sessionmgr4005&vid=4&hid=4213&bdata=JnNpdGU9ZWRzLWxpdmUmc2NvcGU9c2l0ZQ%3d%3d#db=dme&AN=900287. Updated January 25, 2011. Accessed February 9, 2014.
  5. Horner syndrome. Clinical and Experimental Optometry. 2007; 90: 336-344. Available at http://www.academia.edu/408995/Horner_SyndromeAccesses February 9, 2014
  6. Horner’s syndrome. In the first of a three-part series on pupils, Dr Andrew Gurwood looks at Horner’s syndrome. In OptometryToday [database online]. http://www.optometry.co.uk/uploads/articles/01a6c2aba55fdd8939103cd3e6c1e341_Gurwood1990604.pdf. Accessed March 7, 2014.
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