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A 60-year-old male presented with a number of unusual signs and symptoms in the facial region. Among others, it was found that the right side of his face was flushed (red). Further testing revealed a lack of ability to sweat in the same cutaneous region. Which nervous structures were most likely implicated in this set of clinical abnormalities?
A. Cranial outflow of the ANS
B.Dorsal roots of cervical nerves
C.Gray rami communicantes of T 5
D.Sympathetic nerve fibers
E.Vagus nerves
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D.Sympathetic nerve fibers
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The correct answer is: D sympathetic nerve fibers
The sympathetic nerve fibers control the tone of the vasculature and allow for vasoconstriction. If these fibers are damaged, vessels will not be able to vasoconstrict and they will dialate, producing a flush. The cranial outflow of the autonomic nervous system refers to parasympathetic nervous fibers, which do not control the tone of the vasculature. Dorsal roots of cervical nerves carry afferent sensory fibers, not sympathetic neurons. The grey rami communicantes are structures that postganglionic sympathetic neurons travel on before rejoining a spinal nerve, so destroying the grey rami communicantes might disrupt the sympathetic outflow. This could be a good answer, except that the T5 spinal nerve will have no effect on the side of the face. Finally, the vagus nerve is a cranial nerve with mixed motor and sensory fibers which carries parasympathetic fibers to many organs. There is much more to come on all of these topics!
