Anisocoria after bilateral sympathicotomy.

The fundamental mechanistic factors in the Schafer phenomenon consisted of pseudo- and true paradoxical phenomena induced in part by the sympathetic section and in part by lesion of the nociceptive paths at the first operation. The mechanistic factor in the second operation hinges upon the “shock” incidental to the general surgical procedure rather than the second sympathetic section. The Schafer phenomenon can be duplicated by operations in other parts of the body, e. g., by section of one sciatic followed some days later by the section of the other sciatic. The most interesting feature of the Schafer phenomenon is the shortening of the period of incubation for true paradoxical dilatation phenomena. This is induced by the shock of the second operation which causes suspension of function in the decentralized neurones situated within, and distal to, the superior cerivcal ganglion.