Anatomical variations of rami communicantes in the upper thoracic sympathetic trunk

The aim of this study was to clearly delineate the anatomical variations of the communicating rami in the upper thoracic sympathetic nervous system and to help develop better surgical method for essential palmar hyperhidrosis.

Anatomical dissections of the upper thoracic sympathetic chains with sympathetic ganglia and communicating rami have been carried out in 42 adult Korean cadavers (male 26, female 16). The rami communicantes were classified into three types (Normal: transverse or oblique rami connected to the intercostal nerve of the same level; AR: ascending rami connected to the higher level; DR: descending rami to the lower level) based on the anatomical relationship of the thoracic sympathetic ganglia to the intercostal nerves. Both sides of the upper thoracic sympathetic nervous system were compared in the same individual. The number of the communicating rami was recorded in 32 cadavers (64 sides). The distance from the rami communicantes to the sympathetic trunk was measured in 26 cadavers (52 sides).

The incidence of AR (ascending rami) and DR (descending rami) arising from the second sympathetic ganglion was 53.6% (45/84), 46.4% (39/84). From the third thoracic sympathetic ganglion, the incidence of AR was 5.9% (5/84) and that of DR was 26.2% (22/84). And in the fourth thoracic sympathetic ganglion, the incidence of AR was 4.8% (4/84) and DR was 8.3% (7/84), respectively. When we compared anatomical structures of both sides among the 42 cadavers dissected, only 14.3% (6/42) had similar anatomy of the rami communicantes bilaterally. Among 32 cadavers (64 sides), the mean number of rami communicantes at the second thoracic sympathetic ganglion was 2.1/2.5 in the left and the right side. At the third and the fourth thoracic sympathetic ganglion, the mean number was 1.9/1.6 and 1.7/1.7 in each side. The mean distance from the thoracic sympathetic chain to the most distal communicating rami of the left and right side at the second intercostal nerve was 7.81/9.40 mm among 26 cadavers. The mean distance of each side was 6.81/7.94 mm at the level of the third intercostal nerve. And at the level of the fourth intercostal nerve, the mean distance was 7.48/10.92 mm, respectively.

On the basis of this study, the anatomical variations of communicating rami could explain some surgical failures and recurrences. Moreover, in addition to the conventional surgical methods (sympathectomy, sympathicotomy, clipping of sympathetic chain and ramicotomy), dividing the inconstant sympathetic pathways (nerve of Kuntz, ascending or descending rami communicantes) on the second, the third and the fourth ribs will help to get better surgical effect.