- First Order Neuron (Preganglionic): Hypothalamus → Spinal Cord
o Caused by a stroke.
- Second Order Neuron (Preganglionic): Spinal Cord → Superior Cervical Ganglion
o Caused by a Pancoast ‘s Tumor at the apex of the lung.
- Third Order Neuron (Postganglionic): Superior Cervical Ganglion → Eye and sweat glands
o Caused by a vascular disorder (migraine, carotid-cavernous fistula)