Horner's Syndrome
This page was last updated: September 17, 2014
Horner's syndrome is the term used for the group of signs produced by paralysis of the cervical sympathetics whether of peripheral or central origin. At times known as the Claude Bernard - Horner's syndrome and also incorrectly as the Hare's syndrome. As a general rule syndrome is unilateral, therefore easier to detect and of localizing value.  The syndrome consists of the following features:

MIOSIS: Appears at once after sympathectomy or block. Difference in size of pupils evident in daylight and accentuated in dim light since pupil does not dilate in dark. Yet pupil contracts briskly to light and convergence since third cranial nerve (thru ciliary ganglion) still controls sphincter pupillae. Homatropine but not cocaine dilates Horner pupil. Cilio-spinal pupil reflex lost.

PTOSIS / NARROWING PALPEBRAL FISSURE: Due to combination of drooping of the upper lid and raising of the lower lid (at times with convex up appearance). Lid droops due to paralysis of non-striated part of levator palpebrae. Since voluntary portion of levator is controlled by 3rd nerve, ptosed lid can be voluntarily raised. Hence ptosis of Horner's syndrome is a pseudo-ptosis.

ENOPHTALMOS: This is usually due to at optical illusion produced by the narrowed palpebral fissure. Evidence favors idea that muscle of Muller although important in animals is vestigal in man and does not contribute to either enophthalmos by paralysis or exophthalmas by stimulation. Occasionally atrophy of orbit contens and hypotony of globe produce some degree of enophthalmos

ANHIDROSIS:  Lack of sweating on ipsilateral side.


Horner's Syndrome: Notice the left pupil is smaller than the right.  The left palpebral fissure is also narrower than the right because the left upper eyelid is drooping.

Bechara Y. Ghorayeb, MD
Otolaryngology - Head & Neck Surgery

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