Write about Horner's Syndrome here.

• Ptosis

• Miosis

• Enophthalmos

• Anhydrosis

Characterised by an interruption of the oculosympathetic nerve pathway somewhere between hypothalamus and the eye.  The pathway is a 3 neuron arc:

• First neuron = Hypothalamus -> C8-T4 level of the spinal cord

• Second neuron = Axons pass over apex of lung -> sympathetic chain in the neck -> superior cervical ganglion

• Third neuron = Superior cervical ganglion -> with post-ganglionic axons -> via cavernous sinus -> eye via uveal tract to the dilator of the iris (with long posterior ciliary nerves)

• Post-ganglionic axons also innervate the muscle of Mueller within the eyelid (responsible for initiation of eyelid retraction during eyelid opening)

• Post-ganglionic fibres for facial sweating following external carotid to the sweat glands of the face

Pancoast Tumour is an preganglionic cause