Читать книгу Why It Hurts - Dr. Aneesh Singla - Страница 15

Shortly after becoming a pain specialist, I learned of a rare condition that renders a person completely unable to experience pain. Patients with congenital insensitivity to pain (CIP) are normal in every way except for their inability to feel pain, but their syndrome has a severe impact on their lives. The following case appeared in the Journal of Orthopedic Surgery:

In March 2010, a 7-month-old boy presented with a 4-day history of increasing swelling of the elbow, pseudo-paralysis of the right upper limb, and high fever. The child appeared to be toxic. The sensation of pain was less than expected. Multiple ulcers were noted over both hands and feet and tongue. Pain perception appeared to be completely absent, which the parents stated had been present since birth. The parents also stated the child frequently had self-inflicted wounds over the hands, feet, and tongue. Injections into the skin to test for a response produced no pain. The right elbow was found to be infected, and the patient was taken to the operating room where about 20 ml of infected pus was drained, and complete separation and dislocation of the joint were seen. The child was placed on antibiotics for four weeks. Unfortunately, the damage and erosion to the joint were so severe, the joint was permanently damaged and showed evidence of chronic lingering infection of the bone, called osteomyelitis.

This child suffered from CIP, a genetic disease occurring in roughly 1 out of every 25,000 people. Children afflicted with it have a short life expectancy because, without pain, they have little to no ability to avoid trauma from accidents. Without the ability to use pain as a protective reflex, they can’t reliably avoid the harmful things in their environment. In short, these individuals have no ability to adapt to their environment. Parents of children with CIP cannot trust that a child will cry to indicate that something is wrong and this makes it difficult for them to remedy injuries or illness.

As I learned more about the impact of CIP and other conditions that affect our sensitivity to pain, I began to realize that pain provides a critical survival advantage. When we’re caught in its grasp, it can be incredibly difficult to see it in this positive light, but my experience has shown me that pain is actually one of our greatest allies.

I have tried using the metaphor of gravity to help people put pain into perspective. Gravity, like pain, is simply a part of life. It’s not going anywhere. Like pain, gravity can shape, challenge, and direct you.

While most people don’t think very much about the earth’s gravitational force, it affects everything on the planet. For example, it works against a child learning to ride a bike, who must fight to stay balanced or risk scraping a knee. It can be fun to imagine all the things that might be possible if gravity weren’t as strong: effortlessly slam-dunking basketballs, gracefully floating through the air. In reality, a gravity-free world would be quite harmful. Without the constant pull of gravity on their bodies, astronauts’ muscles and bones atrophy despite the rigorous exercise routines they maintain in orbit. In fact, months in space with little to no gravity result in bones becoming brittle and osteoporotic.

Like gravity, pain helps us. Even though pain is certainly an unpleasant feeling that we have to experience, it would be far more dangerous not to be able to experience it.

Patrick Wall, a pioneer in the field of pain, commented on CIP:

Let us pause here to consider the fact that, very, very rarely, children are born who grow up with no sensation of pain. [They] have been the subject of intense study because they are so fascinating and test all our ideas about the meaning and usefulness of our normal ability to perceive pain.

In an interview with Wall, a Canadian student at McGill University with CIP reported a strong pinch felt merely like a “strong pressure.” Wall continued:

All her other body sensations—touch, pressure, warm, cold, and movement—appeared completely normal. How had she grown up without the massive protection supposedly provided by the withdrawal reflex? She had continuous monitoring by her doctor father, mother, and siblings, who were all aware of her problem. Gross damage such as a cut, burn, or fracture does not need pain to be rapidly detected by the victim. Appendicitis had been diagnosed in her by the signs of fever, inflammation, and gut motility, even though she had no pain. Unusual accidents do occur in such people in novel situations. For example, as a child in the deep Canadian winter, she climbed up to look out of the window and knelt on a hot radiator. One could still see the line scars on her knees as an adult.

The Canadian student died at the age of 22 from osteomyelitis, the same bone infection contracted by the infant described in the Journal of Orthopedic Surgery. Why? Remember what I said earlier about the constant presence of low-level discomfort in our lives, how even as we jog, our stride adjusts to give breaks to parts of the body taking more than normal stress, so they can recover?

Whenever the student was injured in a minor way, this automatic recovery phase did not occur. The surfaces of her joints and ligaments were never given the time to fully recover from stress. This left them in a perpetually weakened state, ill-equipped to face future trivial injuries.

Counterintuitively, severe injuries such as fractures do not have such severe consequences for CIP sufferers. When a limb is severely damaged, it is simply put in a cast and held stationary until the healing is complete. Repetitive minor injuries, on the other hand, demolish the joints of those with CIP over time, particularly the ankles, knees, and wrists. The dead and damaged tissue in the joints then becomes a haven where bacteria can flourish, eating their way through the bone and into the marrow. This explosive invasion, osteomyelitis, is still extremely difficult to treat, even with antibiotics, because the medicine cannot easily penetrate this deeply into the body.

Learning about CIP brought me back to my work in anesthesiology. While under anesthesia, patients have to be cared for with vigilance. Nerve injury can occur if, for example, the patient’s body moves into the wrong position. Even when we’re asleep at home, our bodies feel pain and will adjust to anatomically comfortable positions. Under anesthesia, it falls on the anesthesiologist to vigilantly guard the patient while pain is turned off. Life without pain subjects you to the same need for constant attention.

Golnar Jahanmir, a pediatric dentist at Children’s Hospital in Washington, D.C., works with patients with CIP. In some cases, she and her colleagues have had to remove teeth because a child was continuously biting and producing skin erosions in the mouth. For some children with CIP, what should be pain is actually felt as a tingling that actually drives them to physically harm themselves because they find the sensation stimulating. This brings me back to my childhood. When I’d have a numb lip after a dental procedure, all I wanted to do was to keep biting it. Thankfully for me, that numbness was only temporary.

CIP isn’t the only way our capacity for pain can be lost. Diabetes, a chronic inability to correctly regulate blood sugar, can damage nerves when blood sugar levels are too high for too long. This nerve damage, called neuropathy, can cause patients to lose sensation in their feet and ankles. As with CIP, diabetic neuropathy makes the feet vulnerable to constant, repetitive stress due to walking or running. Because of the patient’s inability to sense the injury, ulcers can eventually occur. Decreased blood flow, also due to diabetes, combined with additional, unremitting pressure on the ulcer can result in infection. By the time these infections are detected, there is often erosion into the bones of the feet, culminating in osteomyelitis. This can result in the loss of the limb or the spread of the infection to other parts of the body.

Another threat to our protective pain response is leprosy. For most of human history, people believed that the disease of leprosy, widespread enough to be mentioned multiple times in the Bible, caused the body’s extremities to rot and fall off. But, as first discovered by the English physician Paul Brand, leprosy’s true effect is to damage the nerves that transmit pain.

After completing extensive work with leprosy patients in India, Brand noticed how patients with the disease would constantly injure themselves without realizing it, resulting in skin ulcers and trauma. One experience at the leprosarium opened his eyes to the effects of the disease, as he later related in his book, The Gift of Pain:

A woman…was roasting yams over a charcoal brazier…The yam fell off the stick, however, and I watched as she tried unsuccessfully to spear it, each jab driving the yam farther underneath the hot red coals. Finally, she shrugged and looked over to an old man squatting a few feet away. At her gesture, obviously knowing what was expected of him, he shambled over to the fire, reached in, pushed aside the hot coals to retrieve the yam, and then returned to his seat.

Aghast, Brand rushed over to examine the old man’s hands. He had no fingers left, only stubs covered in blisters and scars, the pain of which he seemed to be blissfully unaware. This experience led Brand to focus his efforts with leprosy patients on teaching them self-monitoring and constant vigilance. Without pain to warn them of damage to their bodies, they would have to rely on using their eyes. Once he’d successfully taught patients how to do this, the “rotting” effect of leprosy disappeared. Brand’s experiences with leprosy led him to dub pain “God’s greatest gift to mankind.”