Horner's syndrome overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Horner’s syndrome is a clinical syndrome caused by damage to the sympathetic nervous system.

It is named after Johann Friedrich Horner, the Swiss ophthalmologist who first described the syndrome in 1869.^[1][2] 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”.

It is important to distinguish the ptosis caused by Horner’s syndrome from the ptosis caused by a lesion to the oculomotor nerve. In the former, the ptosis occurs with a constricted pupil (due to a loss of sympathetics to the eye), whereas in the latter, the ptosis occurs with a dilated pupil (due to a loss of innervation to the sphincter pupillae). In an actual clinical setting, however, these two different ptoses are fairly easy to distinguish. In addition to the blown pupil in a CN III (oculomotor nerve) lesion, this ptosis is much more severe, occasionally occluding the whole eye. The ptosis of Horner’s syndrome can be quite mild or barely noticeable.

There are no direct complications of Horner’s syndrome itself. However, there may be complications from the disease that caused Horner’s syndrome or from its treatment. The outcome depends on whether treatment of the cause is successful.

An eye examination may show changes in how the pupil opens or closes and eyelid drooping. A complete medical and nervous system (neurological) examination can show whether any other parts of the body are affected.

Treatment depends on the cause of the problem. There is no treatment for Horner’s syndrome itself.

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