Horner’s syndrome

Horner syndrome is a neurologic syndrome with 3 classic components: ptosis, miosis, and anhidrosis. 


It can be caused by a variety of conditions: arises from lesions that involve any of 3 neurons along a complex oculosympathetic pathway.


Constellation of signs that occur when sympathetic innervation to the eye is interrupted.

A functional sympathectomy of the ipsilateral eye and is caused by injury or disruption of the neural plexus that runs from the sympathetic chain, past the apex of the lung, and up the carotid artery to the eye.

Also known as Horner syndrome, Bernard-Horner syndrome, Claude Bernard-Horner syndrome or as oculosympathetic palsy.

It is the combination of drooping of the eyelid, ptosis, and constriction of the pupil, miosis, sometimes accompanied by decreased sweating, anhidrosis, of the face on the same side.

Redness of the conjunctiva of the eye is often also present, as is enophthalmos.

Indicates a sympathetic nervous system problem, a part of the autonomic nervous system.

A lesion at any point in the sympathetic pathway may cause the syndrome.

Signs include mild to moderate ptosis, slight elevation of the lower lid, miosis, and pupil dilation lag.

Ptosis occurs from denervation of the sympathetically controlled Muller muscle in the upper lid.

Elevation of the lower lid is due to denervation of the lower lid muscle analogous to the Muller muscle in the upper lid.

Dilation lag refers to slower pupillary dilation compared to the uninvolved pupil.

Ipsilateral impaired flushing and sweating may occur.

Anhydrosis of the ipsilateral face ot body may occur depending upon the level of the lesion.

If the lesion is postganglionic and occurs after vasomotor and sweat fibers have emerged from the sympathetic ganglion anhydrosis may be absent or confined to to the area above the brow.

Congenital Horner’s syndrome may be associated with hypopigmentation of the involved eye.

Refers to sympathetic paresis that affects the eye.

The exact presentation varies with the site of the lesion, and causes vary from life-threatening to benign condition.

Central sympathetic fibers begin in the posterolateral hypothalamus and descend via the mid brain and pons, ending in the intermediolateral cell column of the spinal cord levels C8-T2.

The sympathetic pathway begins in the hypothalamus, travels down the brain stem, through the cervical spinal cord to the level of the ciliospinal center of Budge-Waller at C8-T1, then over the lung apex, ultimately ascending with the carotid artery into the cavernous sinus to the pupil dilators and the Muller muscle of the lid.

The sudomotor sweat fibers supply the face and exit onto the external carotid and its branches.

The sympathetic nerve pathway has 3 divisions: first order involving the hypothalamus to C8-T1, second order involving C8-T1 to superior cervical ganglia, and third order involving the superior cervical ganglia to the pupil dilators and lid.

At T1 preganglionic fibers exit the spinal cord and enter the cervical sympathetic chain.

The cervical chain is in close association with the apex of the lung and the subclavian artery.

From the sympathetic chain fibers ascend and synapse in the superior cervical ganglion at C3-4 which is at the bifurcation of the common carotid artery.

Pupillomotor fibers exit from the superior cervical ganglion and ascend along the internal carotid artery.

Vasomotor fibers and sudomotor fibers leave the superior cervical ganglion along the external carotid artery to innervate the blood vessels and sweat glands of the face.

Pupillomotor fibers along the internal carotid artery enter the cavernous sinus and join the VIth cranial nerve in the cavernous sinus and enter the orbit through the superior orbital fissure along with the ophthalmic branch of the trigeminal nerve via the long ciliary nerves.

The long ciliary nerves innervate the iris dilator and the Muller muscles

Careful history allows for localization of the lesion causing the syndrome.

Commonly an incidental finding and benign, but may be a manifestation of a serious associated process.

Physical examination for upper and lower lid ptosis, measurement of pupil diameter and reaction to light and accommodation, evaluating extraocular movements, checking for facial sensation, cervical lymphadenopathy and the presence of nystagmus are required to evaluate the syndrome.

Causes include: First order neuron lesions-Arnold-Chiari malformation, basal meningitis, basal skull fractures, basal skull tumors, stroke with lateral medullary syndrome, pontine hemorrhage, neck trauma, pituitary tumor and syringomyelia.

First-order Horner syndrome may be caused by stroke, most commonly Wallenberg lateral medullary syndrome.

Cervical spine disease may cause either a first- or second-order Horner syndrome.

Lung apex lesions may produce a second-order Horner syndrome.

Carotid artery dissection often produces pain and is accompanied by Horner syndrome in many patients.

Causes include: Second order neuron lesions-Pancoast tumor of the lung, birth injury to lower brachial plexus, dissection/aneurysm of the aorta, subclavian artery, or carotid artery, cervical rib, central venous catheterization, traumatic or surgical injury with thyroidectomy, neck dissection, or coronary artery bypass graft, lymphadenopathy, chest tubes, and lesions of the middle ear.

Cavernous sinus disease may produce a third-order Horner syndrome, often accompanied by other symptoms such as diplopia.

Causes include: Third order neuron lesions-internal carotid dissection, paratrigeminal syndrome, carotid cavernous fistula, cluster or migraine headaches, and herpes zoster, carotid or vertebral artery dissection, aortic dissection, traumatic carotid injuries, deep neck infections, cerebrovascular accidents, cerebellar bleeds, cluster headache, and Pancoast tumor of the lung.

Associated with the administration of many drugs.

Clinical findings include partial ptosis of the upper eyelid from loss of sympathetic innervation to the superior tarsal muscle (Müller’s muscle), slight elevation of the lower lid, anhidrosis miosis. enophthalmos, loss of the ciliospinal reflex. and bloodshot conjunctiva.

Flushing on the affected side of the face may occur due to dilation of blood vessels.

The pupil’s light reflex is maintained as this is controlled via the parasympathetic nervous system.

In children, Horner’s syndrome sometimes leads to heterochromia, referring to the difference in eye color between the two eyes.

Heterochromia occurs due to a lack of sympathetic stimulation in childhood interfering with melanin pigmentation of the melanocytes in the superficial stroma of the iris.

Is acquired as a result of disease, but may also be congenital or iatrogenic.

Most causes are relatively benign, but its presence may reflect serious disease in the neck or chest such as a Pancoast tumor or thyrocervical venous dilatation.

May be due to lesion or compression of one side of the cervical or thoracic sympathetic chain.

Horner syndrome reflects deficiency of sympathetic activity on the ipsilateral side of the symptoms.

Conditions clinically associated with Horner’s syndrome include: central lesions that involve the hypothalamospinal tract such as transection of the cervical spinal cord, preganglionic lesions such as compression of the sympathetic chain by a lung tumor, and postganglionic lesions at the level of the internal carotid artery such as a tumor in the cavernous sinus or a carotid artery dissection.

Impaired sweating above the waist affecting only one side of the body, without a Horner’s syndrome, indicates the lesion is below the stellate ganglion in the sympathetic chain.

Diagnostic testing is to apply the alpha-agonist apraclonidine to both eyes and observe the increased mydriatic effect due to hypersensitivity on the affected side of Horner syndrome.


The  differential diagnosis is broad.


One of the most commonly found causes is carotid dissection.


To distinguish the ptosis caused by Horner’s syndrome from the ptosis caused by a lesion to the oculomotor nerve: In the former, the ptosis occurs with a constricted pupil due to a loss of sympathetics to the eye, whereas in the latter, the ptosis occurs with a dilated pupil due to a loss of innervation to the sphincter pupillae.

The ptosis of Horner syndrome can be quite mild or barely noticeable.

Miosis is more marked in dim light, as it may be difficult to notice in bright.


First-order lesions causing Horner syndrome  can occur from the hypothalamus, brainstem, and the intermediolateral spinal cord from C8 through T2: due to stroke, trauma, and tumors. 


Second-order lesions can occur anywhere from the ventral nerve roots of C8 through T2, to the apex of the lung, up the mediastinum, and into the cervical sympathetic chain. 


Third-order or postganglionic lesions may arise from the superior cervical ganglion, extending along the carotid artery, cavernous sinus, and to the eye itself.


The treatment of Horner syndrome involves targeting the underlying source. 


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