Surgical extirpation of portions of the sympathetic nervous system frequently fails to produce precisely that permanent peripheral denervation which is to be expected from text-book diagrams of the anatomical arrangement of the system.
The discrepancies are not uncommon even when the surgical technique is above suspiciion. They can in part, of course, be attributed to variations in the detailed anatomy of the sympathetic trunks or in the pattern of distribution of the branches and communications of these trunks. Such atypical arrangements in the autonomic nervous system are frequent. Thus, for example, during careful dissection of the cadaver, with all the relationships exposed, the correct identification of a particular paravertebral sympathetic ganglion can be very difficult; in the depths of a surgical incision, it is often impossible. But, even when the possibility of the usual anatomical anomalies of the sympathetic nervous system has been excluded, persistence of autonomic activity in unexpected areas may, and in certain regions always does, follow operative removal of parts of the system which should have caused complete sympathetic paralysis in the are or region concerned.
Intermediate sympathetic ganglia, J. D. Boyd, Univ. of Cambridge
