MULTIPLE PROTRACTED CAUDA-EQUINA CONSTRICTIONS CAUSE DEEP DERANGEMENTIN THE LUMBOSACRAL SPINAL-CORD CIRCUITRY IN THE DOG

Neuropathological changes of the neuronal pools and spinal cord circui try in the lumbosacral segments were studied in a canine model of mult iple protracted cauda equina constrictions. Anterograde degeneration o f all sacrococcygeal and L7 dorsal root fibers was detected in S1-S3 a nd lower lumbar segments. A narrow degenerated gracile fascicle was fo und in all thoracic and cervical segments terminating in the gracile n ucleus.; Transneuronal degeneration of middle-sized and large neurons, located in S1-S3 and sporadically in L7 segments, was noted. Identica l transneuronal degeneration was seen in a group of small neurons loca ted in the ventralmost part of lamina VIT in S1-S3 segments. Simultane ously, a terminal degeneration was detected in the lateral cervical nu cleus and in the ventral posterior lateral nucleus of the ventrobasal thalamic complex. Concomitantly, a fully developed retrograde degenera tion affecting motoneurons in the ventrolateral portion of the anterio r horn in S1-S3 segments appeared.