Neurons and pain

Pain is defined as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in these terms". Curiously, there are no neurons whose sole function is to transmit painful information from the viscera. Certainly, we recognize visceral pain , but it is detected by neurons that are sensitive to cutaneous stimulations . That is to say that they will perceive the sensitivity on a territory defined at the level of the skin. It follows from this arrangement that the disorders of the internal organs are sometimes taken for pains of a cutaneous territory .

Referred pain

It can also happen that a patient consults for a painful sensation felt at a place other than his real location, a phenomenon that is designated under the name of referred pain . The most banal clinical example is that of angina pectoris where the painful sensation, due to an insufficient irrigation of the cardiac muscle, is projected towards the top of the rib cage with irradiation towards the arm and the left hand.

Other important examples relate to different types of pain, such as:

• the gallbladder , projected onto the scapula region,
• the esophagus , projected onto the rib cage,
• the ureter (due to the passage of a kidney stone), projected onto the lower abdominal wall,
• the bladder , projected onto the perineum and,
• the pain of appendicitis , referred to the front of the abdominal wall, around the navel.

Knowledge of these phenomena makes it possible to diagnose the real cause of such painful sensations, although it would be easy to misunderstand.