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 th ese 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 invo lved. Following this procedure, neurological testing reveals no additi onal neurological deficit. There is no analgesia to pinprick stimuli a pplied to the body surface, despite the relief of the visceral pain, S ince it is reasonable to attribute the favorable results of limited mi dline myelotomies to the interruption of axons of visceral nociceptive projection neurons in the posterior column, we have performed experim ents in rats to test this hypothesis. The results in rats indicate tha t the dorsal column does indeed include a nociceptive component that s ignals pelvic visceral pain. The pathway includes neurons of the posts ynaptic dorsal column pathway at the L6-S1 segmental level, axons of t hese neurons in the fasciculus gracilis, and neurons of the nucleus gr acilis and the ventral posterolateral nucleus of the thalamus.