Horner's syndrome is a clinical syndrome caused by damage to the sympathetic nervous system. more...
It results in ptosis (drooping upper eyelid), miosis (constricted pupil), and occasionally enophthalmos (the impression that the eye is sunk in) and anhidrosis (decreased sweating) on one side of the face.
In children Horner's syndrome sometimes leads to a difference in eye color between the two eyes (heterochromia). This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris.
It is named after Dr Johann Friedrich Horner (1831-1886), the Swiss ophthalmologist who first described the syndrome in 1869. Several others had previously described cases, but "Horner's syndrome" is most prevalent. In France, Claude Bernard is also eponymised with the condition being called "syndrome Bernard-Horner".
Horner's syndrome is usually acquired but may also be congenital. Although most causes are relatively benign, Horner's syndrome may reflect serious pathology in the neck or chest (such as a Pancoast tumor) and hence requires workup.
Horner's Syndrome is due to a deficiency of sympathetic activity. The site of lesion to the sympathetic outflow is on the ipsilateral side that the symptoms are on. The following are examples of conditions that cause the clinical appearance of Horner's Syndrome:
- First-order neuron disorder: Central lesions that involve the hypothalamospinal pathway (e.g. transection of the cervical spinal cord).
- Second-order neuron disorder: Preganglionic lesions (e.g. compression of the sympathetic chain by a lung tumor).
- Third-order neuron disorder: Postganglionic lesions at the level of the internal carotid artery (e.g. a tumor in the cavernous sinus).
Three tests are useful in confirming the presence and severity of Horner's syndrome:
- Cocaine test - Cocaine blocks the reuptake of norepinephrine resulting in the dilation of a normal pupil. The pupil will fail to dilate in Horner's syndrome.
- Paredrine test
- Dilation lag test
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