[Studies on experimentally induced malformations of the spine and spinal cord: neuropathology of lumbosacral agenesis].

The neuropathology of rats with sacral agenesis were studied. On day 8 of gestation, Donryu rats were given an intraperitoneal injection of trypan blue (40 mg/kg), and the offspring were raised. Sixty (23.1%) out of 260 offspring showed abnormalities in the lower half of the body, tail of hind limbs, and the six-week survival rate of the rats with these abnormalities was 38.3%. The grown malformed rats showed complete or incomplete lumbosacral agenesis. In these rats, the spinal level of motor paralysis corresponded to the vertebral level of malformation, and the average spinal level of sensory disturbance was 4.1 segments lower than that of motor paralysis. In the lumbar enlargement of the spinal cord, the ventral horns and the ventral roots were more hypoplastic than the dorsal horns and the dorsal roots, which seemed to be the cause of the difference in the levels of motor paralysis and sensory disturbance. Rats displayed mirror movements of their hind limbs induced by a similar method, which might have resulted from dysplasia of the ventral region of the lumbar spinal cord.