Pain keeps us alive and helps doctors diagnose

Pain is a condition familiar to all and in no need of definition.

Pain sensation is one sensory perception experienced through our nervous system. Others are touch, vibration, proprioception (or joint position) and temperature, hot and cold. Pain is experienced by all vertebrate animals, but is not perceived by invertebrates with the exception of cephalopods – squids and octopi. Pain perception in fish and crustaceans remains controversial.

There is general agreement that pain perception increases survivability – indeed, vertebrates have much longer life spans than invertebrates. Research has shown that typical human cutaneous (skin) nerves have 83 percent Type C trauma receptors (for severe pain). Rare individuals with congenital pain insensitivity have 24 percent to 28 percent Type C receptors, while rainbow trout have 5 percent and sharks and rays 0 percent. Pain perception probably has little survival value in the aquatic environment.

Getting to the point, pain is the most common symptom or complaint for those entering emergency departments – about 50 percent of those coming through the doors. It is the single most important clue as to what injury or disease process has occurred. The quality of pain, burning, stabbing, cramping, steady, dull, sharp, etc., and the location of pain immensely shorten the long list of what can be wrong. Simply put, there is no reason to be X-raying an ankle when the pain is in the elbow.

Pain signals traverse the peripheral nerves to “connections” in the spine called ganglia, then through the spinal cord to the brain. There, the signals reach our consciousness and are interpreted – take a couple of aspirin, go to the liquor cabinet or the emergency room (or both), even call 911. The sophistication of the nervous system and all its sensors is vastly superior to anything in use for property or home alarms. However, Mother Nature is not without flaws.

We have radiating pain in which pain from a dental abscess can spread into the jaw or to the entire side of a face. Somewhat worse is referred pain, where pain from an injured spleen may be experienced as left shoulder pain. Heart attack pain may not appear in the anterior or left chest but in the neck, jaw or left arm – even just the elbow. Pneumonia low-down in a lung near the diaphragm may masquerade as an abdominal problem, even appendicitis in a child. How can this be?

Because both somatic (skin, mucous membranes) nerves and visceral (abdominal and chest organs) nerves pass through the spinal ganglia, the signals may get crossed before reaching the brain. Thus, referred pain remains a challenge for physicians. Another type of pain, not mentioned in medical school or in textbooks, is “feigned” pain.

The nurses had rolled their eyes. The story, appearance and behavior of a patient demanding narcotics for immobilizing back pain were bogus. At my request, a nurse discharged the patient. Next morning, I was confronted by administration and a complaint. I explained that I had simply denied the patient narcotics. Most fortuitously, however, the incoming doc and nurse had witnessed the patient’s bending over the waiting-room drinking fountain the night before – case and complaint closed – diagnosis, feigned pain. Dr. Fraser Houston is a retired emergency room physician who worked at area hospitals after moving to Southwest Colorado from New Hampshire in 1990.

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