Rôle of Preganglionic Fibers of First Thoracic Nerve in Sympathetic Innervation of Upper Extremity

Abstract

Tel ford 1 and Smithwick 2 have described operative procedures for sympathetic denervation of the upper extremity by means of which the preganglionic fibers in question from the second thoracic nerve downward are interrupted but the inferior cervical and upper thoracic sympathetic ganglia are left in situ and the preganglionic fibers of the first thoracic nerve and the gray communicating rami joining the nerves of the brachial plexus are left intact. The advantages claimed for these procedures are avoidance of the unwanted effects of extirpation of the inferior cervical and upper thoracic sympathetic ganglia, particularly Horner's syndrome and sensitization of the vascular musculature in the affected area to adrenin.

The assumption that preganglionic components of the first thoracic nerve play no part in the sympathetic innervation of the upper extremity, although in accord with certain early experimental data recorded by Langley, 3 is not supported by certain more recent experimental and clinical observations. In view of the importance of complete functional sympathetic denervation of the upper extremity in the treatment of peripheral vascular disease it has seemed desirable to obtain additional data regarding the distribution of the preganglionic components of the upper thoracic nerves by means of anatomical and physiological experimentation. The anatomical experiments have been carried out on cats; the physiological experiments on both cats and dogs.

In the anatomical experiments, some cats were subjected to unilateral section of the roots of the second and third thoracic nerves proximal to the communicating rami and division of the sympathetic trunk below the level of the third thoracic nerve; others were subjected to unilateral section of the roots of the first thoracic nerve, leaving the sympathetic trunk intact. Preparations of the inferior cervical ganglia, taken after degeneration of the divided fibers, in the first series, showed extensive degeneration of the intercellular