Horner's Syndrome

Horner's Syndrome

An interruption of the oculo-sympathetic pathway leading to sympathetic inactivity

= Horner's syndrome (HS)

Clinical Triad of (Click HERE to see picture):

1. Miosis

2. Ptosis

3. Anhidrosis

Anatomy:

Sympathetic pathway extends from hypothalamus via lateral brainstem and cervical cord, with first-order neuron synapsing in ciliospinal center (of Budge) at level of C8-T2, in interomediolateral cell columns

- exits out of T1 nerve root in thoracic sympathetic trunk, over apex of lung and near subclavian artery, passing through stellate ganglion

- synapses in superior cervical ganglion (near bifurcation of common carotid artery)

- sudomotor and vasoconstrictor fibres to face travel then with external carotid artery

- fibres to pupillary dilators and eyelid retractor muscles travel with internal carotid artery to long ciliary nerve and nasociliary nerve (3rd order neuron, post-ganglionic)

- divide from ICA and travel transiently with abducens nerve within cavernous sinus, then with V1 branch of trigeminal nerve

Etiology and Localization of HS:

1. First-order neuron (brainstem and spinal cord) 50-60%

- Stroke (commonly Wallenberg's lateral medullary infarction)

- Neoplasm

- Demyelinating disease

- Syringomyelia

- Transverse myelitis

2. Second-order neuron (pre-ganglionic) 20-30%

- thoracic or neck tumor esp Pancoast's tumor at apex of lung, breast malignancy

- "Rowland-Payne" syndrome with HS + paresis of phrenic, vagus, and recurrent laryngeal nerve (elevation of hemidiaphragm, hoarse voice)

- neck trauma and disc protrusion at C8-T1

- compression from cervical ribs, lower plexus avulsions (eg obstetric), aortic aneurysms, thyroid malignancy, lymphadenopathy

- iatrogenic from thyroidectomy, radical neck exploration / surgery, carotid angiography (in days of direct carotid puncture !), vascular catheters, chest tubes, pacemaker insertion

3. Third-order neuron (post-ganglionic) 20%

NB: will not see facial anhidrosis in this localization

- some similar causes to #2

- vascular headaches (as in autonomic cephalgias, cluster headache)

- cavernous sinus / superior orbital fissure lesion (eg. tumor, aneurysm)

- carotid-cavernous fistula ... usually associated ophthalmoplegia, facial pain

- internal carotid artery dissection (with headache, represents Raeder's paratrigeminal neuralgia)

- nasopharyngeal carcinoma (or tumors at jugular foramen)

- complicated otitis media

- trauma with basal skull fracture

Congenital HS usually due to early brachial plexus injury (at birth), post-viral or with some early tumors

- may see straight hair on side of HS in patients with naturally curly hair !!

Differential Diagnosis:

Anisocoria:

- physiologic anisocoria (up to 0.5-1 mm in 20% of population)

- pharmacologic (eyedrops)

- if greater in light then parasympathetic defect such as CN III palsy, Adie's pupil, iris trauma or scopolamine / atropine effects

Ptosis:

- myasthenia gravis

- CN III palsy (with dilated pupil, may be unreactive, +/- ophthalmoplegia)

- levator dehiscence

Coincidental occurrence of physiological anisocoria and age-related ptosis can mimic closely a Horner's syndrome, but dilatation lag and other subtle features will be absent

History:

- notice pupillary asymmetry (affected side smaller, esp in dark)

- drooping of the eyelid (usually mild)

- when first noticed?

- does the ptosis fluctuate (suggesting neuromuscular dysfunction, not HS)

- is there any double vision (absent in isolated HS; suggests either another cause or associated damage to brainstem / cranial nerve structures by lesion causing HS)

- noticed any change in sweating on affected side of face (implies lesion proximal to carotid bifurcation in post-ganglionic neuron, or pre-ganglionic lesion)

- was the eye ever red (seen in acute stages of HS)?

- any associated brainstem features such as dysarthria, dysphagia, ataxia, vertigo, facial weakness, sensory abnormality (on face or in limbs)?

- any neck symptoms including neck pain (eg carotid dissection), masses palpated?

- pulmonary symptoms such as cough, hemoptysis, dyspnea or pain (suggestive of apical lung tumor)

- ipsilateral arm symptoms including pain, numbness / paresthesias, weakness, wasting suggesting involvement of brachial plexus

- headache (if ipsilateral and facial pain consider carotid dissection; if occipital consider vertebral artery dissection with brainstem infarct)

- any Hx of prior neurological events (such as strokes or demyelinating episodes)

Examination:

Confirmation of Horner's syndrome (Click HERE to see picture):

1. Miosis

- affected pupil smaller, more apparent in dark or dim illumination than in light (where it may be inapparent); also stimulate sympathetics with sudden noise (accentuating anisocoria)

- anisocoria usually mild (0.5 - 1 mm) with paresis of iris dilators

- pupil reacts normally to light and accommodation

- dilation lag found when darken room (affected pupil dilates more slowly)

- may see paradoxical pupillary dilatation on affected side in states of adrenergic hyperactivity (eg emotional excitement or stress) due to denervation supersensitivity to circulating catecholamines

- look for heterochromia iridis (iris is different, lighter color in congenital HS due to depigmentation of iris; rarely can occur in acquired lesions)

- conjunctival injection in acute phase may be seen (loss of vasoconstrictor activity) as can hemi-facial flushing and nasal stuffiness

+/- reduced intraocular pressure and increased accommodation

2. Ptosis:

- usually subtle (2-3 mm) and may be variable (slight fluctuations)

- due to weakness of Muller's muscle (smooth muscle, involuntary retractor of upper lid)

- also get upside-down ptosis of lower lid on that side (due to paresis of inferior tarsal muscle) leading to lower lid drawn up higher (hiding bottom of cornea) vs other side

- may have apparent enophthalmos (eye looks sunken) with narrowed palpebral fissure

3. Anhidrosis:

- check sweating (by palpation) on both sides of face, seeing if less on affected side

- also see if hemibody involved (found with central lesions) vs hemi-face and neck down to clavicle in pre-ganglionic lesions

Looking for Etiology / Localization:

1. Brainstem testing:

- cranial nerve abnormalities (incl. CN V, VII, IX, X) may be seen in BS lesions

- ipsilateral ataxia if cerebellum or its connections affected

2. Examination of the Neck:

- palpate for masses, tenderness

- auscultate for carotid bruits and palpate for pulse present (absent if occlusion)

3. Examination of Limbs:

- look at ipsilateral arm for wasting or weakness suggestive of lower plexus involvement

- loss of reflexes and sensory loss can also be found

Diagnosis:

- initial clinical suspicion confirmed (if necessary) by pharmacologic stimulation of sympathetic pathways

1. Cocaine test

- 2 drops of 10% cocaine instilled into each eye

- prolongs action of norepinephrine on dilator muscle by blocking reuptake (requires its release from nerve terminals by intact oculosympathetic pathway)

- normal pupil will dilate while HS pupil will fail to dilate after 45 minutes (confirming diagnosis of HS); but still need to examine in dim room else bright light will overpower effect as PSNS intact - both eyes look constricted !

NB: metabolites of cocaine will be found in urine for 1-2 days afterwards !

2. 1% Hydroxyamphetamine:

- done only after confirming dx with cocaine test (or clinically) and waiting 24-28 hrs to allow cornea and pupils to recover

- 2 drops to also create sympathomimetic effect but does so by stimulating release of norepinephrine from nerve endings, stimulating dilator muscle

- requires that post-ganglionic (3rd-order) neuron be intact and have normal axoplasmic activity so norepinephrine available for release

- normal pupil will dilate, and also normal or accentuated in HS pupil if pre-ganglionic (first- or second-order) while incomplete dilatation seen if post-ganglionic lesion

NB: direct-acting topical adrenergic agents will dilate pupils of HS (eg. epinephrine solution)

- often becomes larger than unaffected side due to supersensitivity from denervation (in subacute to chronic, but not acute phase)

Localization:

1. First-order (central):

- MRI of head and cervical spine

2. Second-order (pre-ganglionic)

- Chest x-ray +/- CT of chest

- CT or MRI of neck

3. Post-Ganglionic:

- MRA for carotid dissection

- MRI for cavernous sinus lesions

References:

Kline LB, Bajandas FJ. Neuro-Ophthalmology review manual. 4th ed. 1996.

Miller NR, Newman N. Walsh & Hoyts Clinical Neuro-Ophthalmology. 5th ed. 1999.

Last update: July 2004

Reviewed by: pending

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