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- Anatomy:
    - C-8 & T-1 anterior nerve roots convey preganglionic sympathetic fibers for innervation of head & neck
           to corresponding spinal nerves, from which they pass to ganglionated sympathetic chain;
    - further laterally these 2 spinal nerves acquire bulk of postganglionic fibers for the hand and arm;
    - injury of C-8 & T-1 nerve roots does not affect sympathetic innervation of arm but interrupts those to same side of head
           causing vasodilatation, anhydrosis, & dilated pupil (Horner's syndrome)