Hundreds of millions of people worldwide suffer from chronic pain, which is pain that lasts more than three months. Although figures vary from country to country, most studies estimate that about 10% of the world’s population is affected, or more than 800 million people.
The Centers for Disease Control and Prevention estimates that in 2021, about 20% of American adults, or more than 50 million people, suffered from chronic pain. Of those, about 7% had what’s known as high-impact chronic pain, which is pain that significantly limits a person’s daily activities.
In the past, doctors tended to prescribe medications as an easy solution. But the opioid crisis in the United States has led doctors to reevaluate their use of medications and consider new treatments for patients with chronic pain.
The Conversation spoke with Rachael Rzasa Lynn, a pain management specialist at the University of Colorado Anschutz Medical Campus for our podcast The Conversation Weekly. She explains some of the new advances in pain treatment and why there is hope for patients with chronic pain.
What causes chronic pain, at the most basic level?
In general, pain is a complex interaction between tissue injury or inflammation, nerves, and brain processing.
There are several biological processes that can cause pain. Nociceptive pain is the type that occurs in most people who experience acute pain. This is pain that occurs when tissues are injured or potentially damaged in some way, triggering the activation of surrounding nerves. These nerves are like electrical wires that send signals from the injured tissues, through the spinal cord, and up to the brain, where pain is ultimately perceived.
But activating these nerves alone is not enough to cause pain, because these electrical signals are amplified or diminished at several points along their journey to the brain. The brain’s perception of pain is essential, because pain does not occur when people are unconscious.
Nociceptive pain can also result from tissue damage or ongoing inflammation, as in arthritis. In these injuries, peripheral nerves are constantly transmitting information to the brain, resulting in a continuous perception of pain.
There are other conditions, such as diabetic peripheral neuropathy, in which the nerves themselves are damaged. In these cases, the nerves send pain signals to the brain that reflect damage to the nerves themselves, not the tissues from which they originate. This is called neuropathic pain.
In other forms of chronic pain called nociplastic pain, the initial tissue damage may heal completely, but the brain and nervous system continue to generate pain signals.
Many chronic pain conditions actually involve a combination of these three phenomena – nociceptive, neuropathic and nociplastic pain – which adds to the difficulty of diagnosis and treatment.
How do doctors like you measure pain?
I think anyone who has been to a hospital, at least in the United States in the last decade, is familiar with the numeric scale that asks you to rate your pain. It’s a one-dimensional assessment of pain that only asks for its intensity.
But pain is a very complex phenomenon that involves much more than just intensity. So a single numerical value based on pain intensity doesn’t take into account the impact that pain can have on a patient’s daily life, such as their activities, relationships, ability to sleep, happiness, and overall satisfaction with life.
I think the hardest thing about pain, in general, but especially with many forms of chronic pain, is that you can’t see it. There’s no external, validated way to really know how much pain someone is in. We have new methods of measuring pain that try to get at some of the more complex aspects, but it’s still a very incomplete science. It’s all subjective and depends on what the patient tells you about their experience.
What are the most promising new pain treatment options?
A treatment that has recently become popular is called pain reprocessing therapy, which takes a behavioral approach to eliminating pain.
At our medical campus, therapists help patients understand the causes of chronic pain and reappraise sensations they experience as painful, such as when they perform movements that are typically painful for them. The goal of pain reprocessing therapy is to help patients perceive the pain signals sent to their brain as less threatening, so their brains “unlearn” the pain.
Another approach that is gaining new applications is nerve ablation, a procedure in which the nerves around a painful area are anesthetized with drugs and then intentionally damaged. In this case, doctors inject a chemical around the nerves or gently heat them so that they can no longer send pain signals effectively for months or even years. This approach has been used for decades for spinal pain, but it is now being applied more broadly to pain originating elsewhere in the body.
A similar approach involves using electricity to stimulate the nerves that serve a painful area to change or block the way pain signals travel through them. This method involves placing a tiny electrical device along the nerve to deliver a low level of electricity. This is an example of neuromodulation, which is increasingly being used to treat a wide variety of chronic pain conditions throughout the body, from foot pain to migraines. It has even shown promise in managing acute pain after surgeries like knee replacements.
A classic example of neuromodulation is spinal cord stimulation, which is used to treat a variety of conditions that cause chronic pain. A surgeon places wires under the bones of the back, but outside of the spinal cord and spinal fluid. The wires are connected to a battery, much like a pacemaker battery, which delivers electrical signals to the nerves in the spinal cord to scramble the pain signals.
Images by Cinefootage/iStock via Getty Images
What role did the opioid crisis play?
These new treatment options for patients with chronic pain may not have advanced as quickly without the opioid crisis.
For decades, opioids have been overprescribed to treat chronic pain. Yet some patients with chronic pain can actually benefit from opioids in terms of pain relief and improved quality of life. In my opinion, doctors have overcorrected, to the point where it is now difficult for these patients to access the opioid treatments that have worked so well for them. Partly because of the slowdown in opioid production in recent years, in some parts of the United States, many patients no longer have access to these medications at all.
Researchers are now working to identify new drugs that relieve pain without the risks of addiction and overdose that opioids, including cannabinoids, pose. In recent years, patient care has shifted away from medications to behavioral and procedural interventions, including neuromodulation.
Looking to the future: what’s next?
I think the holy grail of pain medicine is determining which patients with the same condition will respond to the same treatment. For example, two patients with a degenerative tissue disease like knee osteoarthritis may have nearly identical X-rays and yet their pain experience and response to treatments are completely different. One patient may respond well to physical therapy, while another may not improve with physical therapy alone and may require multiple medications, injections and eventually surgery – and potentially continue to live with pain.
Researchers like me don’t yet know what characteristics distinguish one patient from another in terms of outcomes. That means current treatment plans involve a lot of trial and error, which can be slow and frustrating for patients with pain.
My goal and main hope for the future of pain medicine is that researchers find a better way to predict who will respond to a particular treatment, which would allow them to match each patient to the right treatment regimen the first time.