January 17, 2007

Horner Syndrome

Synonyms and related keywords: Bernard-Horner syndrome, Horner syndrome, Horner's syndrome, oculosympathetic paralysis, Raeder paratrigeminal syndrome, heterochromia irides, miosis, constricted pupil, partial ptosis, loss of hemifacial sweating, anhidrosis


Background: Horner syndrome results from an interruption of the sympathetic nerve supply to the eye, and is characterized by the classic triad of miosis (ie, constricted pupil), partial ptosis, and loss of hemifacial sweating (ie, anhidrosis).

Pathophysiology: Sympathetic innervation to the eye consists of a 3-neuron arc. First-order fibers descend from the ipsilateral hypothalamus through the brain stem and cervical cord to T1/T2. These fibers synapse on ipsilateral preganglionic sympathetic fibers, exit the cord, travel to the sympathetic chain as second-order neurons to the superior cervical ganglion, and then synapse on postganglionic sympathetic fibers. The third-order neurons travel via the internal carotid artery to the orbit and innervate the (dilator) radial smooth muscle of the iris.

Postganglionic sympathetic fibers also innervate the muscle of Mueller within the eyelid. This muscle is responsible for initiating eyelid retraction during eyelid opening. Postganglionic sympathetic fibers responsible for facial sweating follow the external carotid artery to the sweat glands of the face. Interruption at any location along this pathway results in ipsilateral Horner syndrome.

Horner syndrome may result from the following conditions:


Mortality/Morbidity: The implications of disease depend on the underlying cause.

Race: No known racial predilection exists.

Sex: No known sexual predilection exists.

Age: No known age predilection exists.


History: Symptoms depend on the underlying cause.


Causes: Horner syndrome can be congenital, acquired, or purely hereditary (autosomal dominant). The interruption of the sympathetic fibers may occur centrally (ie, between the hypothalamus and the fibers' point of exit from the spinal cord [C8 to T2]) or peripherally (ie, cervical sympathetic chain, superior cervical ganglion, along the carotid artery).


Other Problems to be Considered:

Simple anisocoria
Senile miosis
Argyll Robertson pupil
Miotic drugs
Holmes-Adie pupil (contralateral)


Imaging Studies:



Medical Care: In general, appropriate treatment depends on the underlying cause. In many cases, no effective treatment is known. The goal of treatment is to eradicate the underlying disease process. Recognizing the presence of the syndrome and expedient referral to appropriate specialists are tantamount to early diagnosis.

Consultations: Patients may require consultations with appropriate specialists (eg, pulmonologists, neurologists, internists) to manage the underlying cause.




Medical/Legal Pitfalls:

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