Horner's syndrome

Horner's syndrome
Synonyms	Bernard-Horner syndrome, oculosympathetic palsy
Left-sided Horner's syndrome
Classification and external resources
Specialty	neurology
ICD-10	G90.2
ICD-9-CM	337.9
OMIM	143000
DiseasesDB	6014
MedlinePlus	000708
eMedicine	med/1029 oph/336
Patient UK	Horner's syndrome
MeSH	D006732
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Horner's syndrome is a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged. The signs and symptoms occur on the same side as the lesion of the sympathetic trunk. It is characterized by miosis (a constricted pupil), partial ptosis (a weak, droopy eyelid), apparent anhidrosis (decreased sweating), with or without enophthalmos (inset eyeball).

The nerves of the sympathetic trunk arise from the spinal cord in the chest, and from there ascend to the neck and face. The nerves are part of the sympathetic nervous system, a part of the autonomic (or involuntary) nervous system. Once the syndrome has been recognized, medical imaging and response to particular eye drops may be required to identify the location of the problem and the underlying cause.

Signs that are found in patients on the affected side of the face include

Interruption of sympathetic pathways leads to several implications. It inactivates the dilator muscle and thereby produces miosis. It inactivates the superior tarsal muscle which produces ptosis. It inactivates the orbitalis muscle which produces the effect of enophthalmos. It also reduces sweat secretion in the face.

Sometimes there is flushing on the affected side of the face due to dilation of blood vessels under the skin. The pupil's light reflex is maintained as this is controlled via the parasympathetic nervous system.

In children, Horner's syndrome sometimes leads to heterochromia, a difference in eye color between the two eyes. This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris.

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Wikipedia