Horner's syndrome involves interruption of the sympathetic nerve supply to the pupil, while the parasympathetic nerve supply is intact. The affected pupil is smaller, especially in the dark.


Synonym: Claude-Bernard-Horner Syndrome


Nerves involved:

(1) first neuron (central): brainstem and spinal cord (hypothalamus to ciliospinal center of Budge at spinal cord level C8-T2)

(2) second neuron (preganglionic): spinal cord, sympathetic chain below superior cervical ganglion

(3) third neuron (postganglionic): superior cervical ganglion to pupil (runs adjacent to internal carotid and ophthalmic arteries)


Mechanism of injury:

(1) cerebrovascular accident (stroke): first neuron

(2) CNS neoplasm: first neuron

(3) demyelinating disease: first neuron

(4) syringomyelia: first neuron

(5) neck trauma): first neuron, second neuron, third neuron

(6) obstetrical epidural block: first neuron

(7) apical bronchial carcinoma (Pancoast tumor): second neuron

(8) mediastinal lymphoma: second neuron

(9) mediastinal metastases: second neuron

(10) cervical rib: second neuron

(11) neck abscess: second neuron, third neuron

(12) thyroid neoplasm: second neuron, third neuron

(13) cervical lymphadenopathy: second neuron, third neuron

(14) s/p thyroidectomy: second neuron

(15) s/p cervical sympathectomy: second neuron

(16) radical neck surgery: second neuron

(17) carotid angiography: second neuron

(18) insertion of central line in the internal jugular vein: second neuron

(19) internal carotid artery dissection: third neuron

(20) cluster headache: third neuron

(21) Raeder's syndrome (ipsilateral hemicrania): third neuron

(22) cavernous sinus disorder: third neuron

(23) orbital fissure disorder: third neuron

(24) carotid-cavernous sinus fistula: third neuron

(25) complication of otitis media: third neuron

(26) nasopharyngeal carcinoma: third neuron

(27) skull fracture: third neuron


Clinical features:

(1) unilateral miosis (rarely bilateral) which is maximal in the dark. The pupil with the interrupted sympathetic nerve supply is affected. Bilateral miosis may occur in diabetic autonomic neuropathy or with primary amyloidosis and may be difficult to detect.

(2) pupil redilitation lag (pupillary redilatation after a light reflex is slowed)

(3) upper lid ptosis (1-2 mm)

(4) lower lid ("upside down") ptosis (elevation of lower eyelid)

(5) apparent enophthalmos (from narrowing of the palpebral fissure; exclude true enophthalmos with exophthalmometry)

(6) facial anhydrosis (if first or second neurone involved, usually forehead above eyebrow on the affected side)

(7) conjunctival injection

(8) loss of iris pigment (heterochromia): if congenital or of very long duration


Pharmacologic testing:

(1) cocaine 4% drops: affected pupil dilates less, causing increased anisocoria (poor dilitation, loss of mydriatic response)

(2) OH-amphetamine 1%, pholedrine 0.5-1%: If third neuron injury (postganglionic) then affected pupil dilates less and anisocoria increases. If first or second neuron injury (central or preganglionic), then both pupils dilate equally, so that the anisocoria is reduced or disappears..


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