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THE MERCK MANUAL MEDICAL LIBRARY: The Merck Manual of Diagnosis and Therapy
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Horner's Syndrome

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Horner's syndrome is ptosis, miosis, and anhidrosis due to dysfunction of cervical sympathetic output.

Horner's syndrome results when the cervical sympathetic pathway running from the hypothalamus to the eye is disrupted. The syndrome may be central, preganglionic, or postganglionic in origin; it may be primary or secondary to another disorder. Central lesions include brain stem ischemia, syringomyelia, and brain tumor; peripheral lesions include Pancoast tumor, cervical adenopathy, neck and skull injuries, aortic or carotid dissection, and thoracic aortic aneurysm. A congenital form exists.

Symptoms include ptosis, miosis, anhidrosis, and hyperemia of the affected side. In the congenital form, the iris does not become pigmented and remains blue-gray. Liquid cocaine 10% can be applied to the affected eye; poor pupillary dilation after 30 min indicates Horner's syndrome. If results are positive, 1% hydroxyamphetamine solution or 5% n-methyl hydroxyamphetamine can be applied to the eye 48 h later to determine whether the lesion is preganglionic (if the pupil dilates) or postganglionic (if the pupil does not dilate). Patients with Horner's syndrome require MRI or CT of the brain, spinal cord, chest, or neck, depending on clinical suspicion.

Any identifiable causes are treated; there is no treatment for primary Horner's syndrome.

Last full review/revision November 2005

Content last modified November 2005

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