Is There a Pathway in the Posterior Funiculus That Signals Visceral Pain?

The present report provides evidence that axons in the medial part of the posterior column at T10 convey ascending nociceptive signals from pelvic visceral organs. This evidence was obtained from human surgical case studies and histological verification of the lesion in one of these cases, along with neuroanatomical and neurophysiological findings in animal experiments. A restricted lesion in this area can virtually eliminate pelvic pain due to cancer. The results remain excellent even in cases in which somatic structures of the pelvic body wall are involved. Following this procedure, neurological testing reveals no additional neurological deficit. There is no analgesia to pinprick stimuli applied to the body surface, despite the relief of the visceral pain. Since it is reasonable to attribute the favorable results of limited midline myelotomies to the interruption of axons of visceral nociceptive projection neurons in the posterior column, we have performed experiments in rats to test this hypothesis. The results in rats indicate that the dorsal column does indeed include a nociceptive component that signals pelvic visceral pain. The pathway includes neurons of the postsynaptic dorsal column pathway at the L6-S1 segmental level, axons of these neurons in the fasciculus gracilis, and neurons of the nucleus gracilis and the ventral posterolateral nucleus of the thalamus.