Referred pain

One of the first symptoms of a heart attack can be pain in the teeth and/or jaws. In the case of a heart attack, the presence of pain in the teeth or jaws doesn't mean that there is any dental condition that needs to be treated, in the absence of any pre-existing dental condition. The experience of dentally related pain during a heart attack is a classical example of referred pain which is pain felt at a site distant from the site of origin. But referred pain can also occur under less dramatic circumstances unrelated to any cardiac pathology. Thus pain referral is frequently found in patients with chronic musculoskeletal pain (for example, temporomandibular disorder (TMD), fibromyalgia, and chronic low back pain). In patients with TMD, for example, muscle and/or jaw joint pain could refer to the teeth and other parts of the orofacial area. Patients and clinicians alike can become convinced that the pain is actually due to some form of dental pathology and there are clinical cases where tooth extractions have been carried out in the mistaken belief that there is a dental cause to the pain. In these circumstances, tooth extractions have no effect whatsoever on the cardiac pain. How does pain referral arise? Is the patient imagining the pain? Or is there a neural basis for pain referral? Are there any diagnostic tests that can be done to help distinguish pain referral to a tooth as distinct from pain arising in that tooth? Pain referral is, indeed thought to have a neural basis. Specific pathways and neural connections in the brain are thought to lead to the possibility of pain referral. Convergence is one of the important neural phenomena that plays a critical role in pain referral. To understand convergence it is necessary to revise our understanding of how sensory information enters into and is processed in the brain. Information about touch and tissue damage is conveyed as action potentials along specific sensory nerve fibres that have their sensory receptors in the periphery (e.g. muscle, skin, joint, tooth pulp). One group of nerve fibres conveys information about touch and another group conveys information about tissue damage or noxious stimulation. The sensory nerve fibres conveying information about noxious stimuli are called nociceptive nerve fibres. Both the nociceptive and the touch nerve fibres convey action potentials into the brainstem to terminate on second order neurones in the trigeminal …