Horner Syndrome

Horner syndrome is a rare condition classically presenting with partial ptosis (drooping or falling of upper eyelid), miosis (constricted pupil), and facial anhidrosis (loss of sweating) due to a disruption in the sympathetic nerve supply. It is primarily acquired following damage to the sympathetic nerve supply, but rare cases of congenital forms have been seen. Therefore, treatment is centered around identifying and appropriate management of the underlying secondary cause.

The syndrome has several names, such as Bernard-Horner syndrome (French-speaking countries), Horner syndrome (English speaking countries), oculosympathetic palsy, and Von Passow syndrome (Horner syndrome in association with iris heterochromia).

The syndrome was first described by Francois Pourfour du Petit in 1727 when considering results from an animal experiment involving resection of intercostal nerves and subsequent changes seen in the ipsilateral eye and face. It was outlined more thoroughly by the French physiologist Claude Bernard in 1852, followed by several physicians who offered different interpretations.

The condition was formally described and later named after Swiss ophthalmologist Johann Friedrich Horner in 1869.

Anatomy

Understanding the sympathetic innervation of the eye is vital to understanding the features of this syndrome. The nerve supply is constituted by three different neurons, starting from the posterolateral hypothalamus and ending as the long ciliary nerves to supply the iris dilator and superior tarsal muscles (Müller muscle).

The first-order neurons originate from the hypothalamus and descend through the midbrain and pons uncrossed, terminating at the C8-T2 level of the spinal cord in the intermediolateral cell columns (ciliospinal center of Budge). Second-order preganglionic neurons exit at the T1 level of the spinal cord to enter the cervical sympathetic chain, where the fibers ascend to synapse in the superior cervical ganglion at the C3-C4 level.

Third-order, postganglionic fibers branch off into the sudomotor and vasomotor fibers, which follow the external carotid artery and innervate the sweat glands and blood vessels of the face. The remaining fibers ascend along the internal carotid artery in the carotid plexus to eventually enter the cavernous sinus, where they join the abducens nerve (CN VI). The fibers then exit the cavernous sinus to enter the orbit via the superior orbital fissure and the ophthalmic branch (V1) of the trigeminal nerve (CN V) as the long ciliary nerves.