Write about Horner's Syndrome here.
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