Horner’s Syndrome

Something as ‘minor’ as a drooping eyelid may herald a diagnosis of an underlying cancer, or life threatening carotid dissection.

Horner’s syndrome is damage to the sympathetic nerve supply to the eye – oculosympathetic palsy. It’s features are usually described as the medical triad

  1. Ptosis
  2. Miosis (small pupil)
  3. Anhidrosis (loss of sweating on one side of face)

Although fairly rare, it is common in exams, and can be the presenting feature of some important diagnosis.


Which of the following are possible causes of a Horner’s syndrome?

    • Breast cancer
    • Lung Cancer
    • Bowel Cancer
    • Carotid Artery stenosis
    • Carotid Artery Dissection
    • Brainstem Stroke
    • Migraine
    • Cluster Headache
    • Tension Headache

How can the small pupil (miosis) be identified during examination?

For a full introduction to horner’s syndrome watch my video, the full transcript is below.


Motor supply of pupil movements is by the autonomic nervous system, with the sympathetic nervous system supplying the pupil dilation, and the parasympathetic system controlling constriction.

A defect of the sympathetic supply to the eye, also called an oculosympathetic palsy is horner’s syndrome.
It makes the affected pupil smaller or meiotic, causing the pupils to be unequal in size. This pupillary size difference is termed anisocoria.

Here, the right pupil is slightly smaller than the left. When the lights are switched off this anisocoria becomes more obvious as the normal left pupil dilates. The affected right pupil may also dilate, but more slowly, this is called a dilation lag. The anisoria may therefore be greatest a few seconds after switching off the room lights.

Another feature of horner’s, illustrated here, is an upper and lower lid ptosis, making the upper and lower eyelids slightly closer together and making the eye appear smaller. The patient may also notice a loss of sweating on one side of the forehead or face, called anhidrosis.

We therefore have a triad of ptosis, meiosis and anhidrosis.

If the horner’s syndrome is congenital, or occasionally if longstanding, then iris heterochromia may also be noted. The affected iris being lighter in colour than the other eye.

Horners syndrome can be confirmed pharmacologically by use of apraclonidine 0.5%, commercially available as iopidine drops. First measure the pupil sizes – this is readily acheived by taking a quick photo with a digital camera. Then instill a single drop of apraclonidine into each eye. After 1 hour re-examine the pupils. Horners syndrome is confirmed if the anisocoria is reversed, since apraclonidine has no affect on the normal pupil, but dilates the affected pupil. The ptosis may also disappear. Care is needed with infants under 6 months, as they have been reported to become very lethargic after this test.

An alternative test is the Cocaine 4% test. Here a single drop is instilled in each eye and the eyes re-examined after 1 hour. The cocaine dilates the normal pupil but has little or no effect on the horner’s pupil. The anisocoria is therefore increased, most noticeably in light conditions.

Having now diagnosed a horners syndrome, we need to try to locate the cause.
This is divided into 3 groups along the oculosympathetic pathway. Central, preganglionic and postganglionic. It does not cross sides along its entire course.

The central pathway arises at the hypothalamus, then travels down the brainstem and cervical spinal cord to synapse at the ciliospinal centre of budge between C8 and T2. Central horners syndromes are usually not an isolated clinical finding, instead they are part of a wider clinical picture featuring other brainstem or spinal symptoms and signs. Causes of central lesions include stroke, tumour, syrinx, vascular malformations, trauma or demyelination. An example is Lateral Medullary or Wallenberg Syndrome, caused by Posterior Inferior Cerebellar Artery Ischaemia. This features dysphagia, analgesia in ipsilateral face and contralateral trunk and extremities, ipsilateral cerebellar ataxia, and rotary nystagmus; skew deviation may occur, with vertical diplopia. Suspected central lesions are usually investigated by imaging with MRI.

From the ciliospinal centre the second order neurone leaves the spine and joins the sympathetic chain close to the lung apex and passes up to synapse at the superior cervical ganglion in the neck. This preganglionic pathway is damaged in a number of ways. The T1 nerve root may be damaged at birth, with an associated brachial plexus palsy causing hand weakness, termed a klumpke palsy. Compression at the pulmonary apex may arise from pancoast lung tumour or breast cancer and also, TB, cervical rib or vascular anomolies. There may be associated shoulder tip or arm pain where the brachial plexus is affected. This presentation would indicate the need for a Chest X-ray and appropriate referall. Neck surgery or trauma may also injure this preganglionic part of the pathway.

The postganglionic pathway passes from the superior cervical ganglion onto the carotid plexus. It ascends with the internal carotid artery to the cavernous sinus. Here the fibres join the ophthalmic branch of the trigeminal nerve passing through the superior orbital fissure into the orbital apex and becoming the long ciliary nerve before entering the eye. Sweating is not usually affected by postganglionic horners lesions due to divison of the nerve supply at the carotid bifurcation. A horner’s syndrome associated with unexplained neck or facial pain should be considered as a carotid dissection and promtly investigated usually by MR Angiography.

A horner’s syndrome associated with a gaze palsy should lead to investigation of the cavernous venous sinus region, usually with an MRI.

Cluster headache often features transient horner’s syndrome during the attack. Men are affected 6 times more than women. Features of cluster headache are severe headache around the eye or temple associated with lacrimation and redness, blocked or watering nose and sweating all on the one side. The attacks last 30 minutes to 2 hours, are often 1 to 2 times per day and after 4 – 8 weeks they stop, on average for around a year. They are both debilitating and treatable, with verapamil and steroids effective for prophylaxis.

2 thoughts on “Horner’s Syndrome

  1. Janet Williams

    I was diagnosed with Horners Syndrome after mitral valve repair surgery 1 month ago. Since it was the result of interference of the nerves with catheter insertion in the carotid what are the chances of recovery of my drooping eyelid, and slow responding pupil?

    1. Jeff Clark

      Janet Williams , none the headache may go away but the eye damage will always be with you . 2010 a chiropractor moved to my little mid west town , I was having back pain he took a jack hammer to my neck and 3 weeks later my eye lid dropped and my pupil would not change , 2013 my eyes started to drift my left eye is off by 60 degree , purism glasses only go to 20 , im not getting blood flow to the eye they do offer surgery cut the muscles that control the eye movement , but im scared with no blood flow i will lose my left eye , both eyes work i have 20 /20 vision just see 2 of every thing each eye is working on its own , at first it was like watching a tv over a tv now the 1 tv is 60 foot in the air at 100 foot . i have over come the 2 over laying images and drive and ride a motorcycle . but a zero chance of any recovery.


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