Where do fibers for sympathetic supply to structures in head and neck arise?

Sympathetic fibers originate in the intermediolateral column of the spinal cord at the levels of T1 down to about L2. Then the fiber travels out to the sympathetic trunk which runs parallel and lateral to the spinal cord from T1-L2. Inside the sympathetic trunk, the fiber synapses with another fiber which makes its way up into your head and neck.