Onuf's motoneuron is resistant to poliovirus

Onuf's nucleus, located in the anterior horn of the sacral spinal cord, has been shown to innervate the striated muscles of the urethral and anal sphincters and is known to be well preserved in patients who have motoneuron disease. To answer the question whether the nucleus is also safe from motoneurotrophic virus infections, we examined the spinal cords of 3 individuals who had suffered severe poliomyelitis. In 2 of these which were acutely fatal cases, all motoneurons were damaged by neuronophagia, but Onuf's nucleus escaped the inflammatory degeneration. In a chronic case, neuronal loss in the anterior horn with replacement by gliosis was prominent below the thoracic cord down to the sacral cord, but Onuf's nucleus was well preserved. Thus, Onuf's nucleus appears to differ from other motoneurons with regard to susceptibility to poliovirus infection.