Transganglionic degeneration in the spinal trigeminal nucleus following removal of tooth pulps in adult cats

Abstract

It is generally thought that transganglionic degeneration of central axons following lesions of their peripheral processes does not occur in adult nervous systemS, 6. For this reason there has been a lack of anatomical descriptions of the central distribution of specific groups of peripheral sensory axons. We, however, have found reproducible axonal and terminal degeneration in specific regions of the spinal trigeminal nucleus in adult cats following tooth pulpectomies 12. Healthy adult cats were used and the absence of dental pathology was confirmed prior to operation and in the controls. Under pentobarbital anesthesia and using appropriate aseptic dental procedures, the pulps were completely removed from all of the teeth on one side of 12 animals. Following postoperative survival times of 7, 9, 11, 14, 21, 28 and 100 days the animals were perfused with 4~o formaldehyde in a phosphate buffer 11. Transverse frozen sections through the brain stem, including the major parts of the spinal trigeminal nucleus, were stained by either the NautaGygax v or the Fink-Heimer (I) 4 technique. Two normal, unoperated animals were sacrificed and processed in the same fashion to serve as controls. Fig. 1 illustrates the pattern of degeneration observed at 1 l days. Unequivocal axonal and terminal degeneration (Fig. 2) is seen predominantly in the ventral half to one-third of the subnucleus interpolaris of the spinal trigeminal complex, near and immediately rostral to the obex, with very much less in the adjacent subnuclei (caudalis and oralis). The distribution is bilateral, but heaviest on the side of the lesion. The occurrence of contralateral degeneration is surprising in view of what is known of the organization of this system 2, but it is a consistent finding here. A crossing pathway of degenerating fibers cannot be identified with certainty. The amount of degeneration is less at shorter or longer survivals, but the pattern is similar in each. Control animals, with healthy teeth, show no degeneration.