28/04/2024
Viscerosomatic and Viscerovisceral Convergence 💡
👉 Viscerosomatic convergence of sensory pathways plasy an important role in the manifestation of acute and chronic visceral pain syndromes, contributing to referral of pain to somatic sites and to the coexistence of pain states affecting more than one organ. (https://pubmed.ncbi.nlm.nih.gov/10700338/, https://pubmed.ncbi.nlm.nih.gov/15940629/)
👉 Both visceral and somatic afferent signals synapse on the dorsal horn of the spinal cord. Visceral afferents are thought to represent less than 10% of all afferent signal inflow into the spinal cord, a relatively small number. (https://pubmed.ncbi.nlm.nih.gov/22246042/). Visceral afferent terminals also show extensive divergence and intraspinal distribution compared to cutaneous afferents. (https://pubmed.ncbi.nlm.nih.gov/11076915/)
🤕 The convergence of afferent visceral and somatic signals into the supraspinal centers is thought to generate the symptoms of referred pain felt by many patients. Despite these neurons initially being activated by visceral nociceptors, central processing can create the perception that the input is arising from various somatic dermatomes, resulting in pain perception distant to the primary site. This convergence of visceral and somatic messages may be one reason for visceral pains often accompanying somatic pain conditions or vice versa. In addition there can be viscero-visceral convergence whereby pain from one organ is referred to another.
🤕 An example of viscerosomatic convergence is illustrated in the figure below (https://shop.elsevier.com/books/pain-care-essentials-and-innovations/pangarkar/978-0-323-72216-2):
👉 In this case, pain from the gallbladder can sometimes be felt in the abdominal region as well as the shoulder and scapular region.