Pain syndromes in the cervicobrachial region may be an expression of irritation of the periarterial autonomic nervous system. They show a vasal, arterial topography (here of the subclavian artery). If the cervical sympathetic chain is involved in the irritation, the area supplied by the carotid artery, i.e. the homolateral half of the head is also affected. Characteristics of these disturbances are their abnormal topography, which cannot be classified either as a radicular nor a segmental pattern. In this region the perception of pain is delayed. The quality of pain is protopathic (dull, intense, burning). In the sympathalgia region there is lowering of the pain threshold (dysesthesia), vasomotor disturbance (dyskinesia) local homeostatic disorders (dyscrasia), in certain circumstances trophic disturbances (dystrophy) which are usually accompanied by marked depression (dysthymia).
1: MMW Munch Med Wochenschr. 1979 Sep 14;121(37):1167-72.
http://www.ncbi.nlm.nih.gov/pubmed/114792