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Why Pain Hurts: Understanding Pain and the Brain

Last updated: 04-22-2020

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Why Pain Hurts: Understanding Pain and the Brain

This story is the first installment of a three-part Exploring Your Health episode delving into the science of pain and the latest methods of treatment. All three parts are available now:

Airforce Lieutenant Colonel Tom Norris was 35 when he diagnosed himself with testicular cancer. He was stationed in Saudi Arabia at the time, it was six months before he could return to the U.S. to have his tumor removed.  By then, it had grown to the size of a large grapefruit.

“Either I got too much radiation or I reacted adversely to too much radiation. So about a year later I started having pain in my left hip. And it has gotten worse.” Norris says within two years he was unable to walk. “It took a urologist to look at my x-rays and she was able to see all the scar tissue from my left hip to the pubic bone and then up.”

It was the beginning of Norris’ epic journey of pain. Confined to a bed, Norris says his health issues compounded, “I've got nerve damage. I've got muscle damage. I've got scar tissue. I've got neuropathy. I've got fibromyalgia. Every one of my vertebrae is screwed up.”

He and his wife, Marianne Muellerleile, a well-known actor, sought every treatment imaginable. “We've done electricity, we've done magnets, we've done faith healing, we've done at distance healing, we've done bee stings,” said Norris, “You name it, anything that's on the list, we've tried it and I spent 10 years in bed unable to do anything.” 

The moment an injury happens, the pain felt is actually a gift of sorts. It warns us, protecting us from further injury. But when it becomes a constant, insufferable presence, pain can suck the joy out of life. More than 20 percent of adults, like Norris, struggle with chronic pain. The prevalence is even higher among those living in poverty. 

Scientists are trying to find better, non-addictive ways to treat pain.  The first step may be changing how we think about pain.

Traditionally, treatment has focused on the site of injury, like a knee that hurts or a back that aches.

These days, doctors and researchers are honing in on the role the brain plays.

Dr. Sean Mackey, Chief of Stanford Medicine’s Pain Division, says the way we experience pain is shaped by a myriad of things. “It's shaped by our early childhood life experiences. It's how our parents treated us when we had an injury and had pain,” said Mackey. “It's our genes, it is changed by the amount, for instance, of anxiety or depression that we may have.”

For some though, the brain gets confused and makes pain the new normal.

“What happens in some people, and we're still trying to understand this,” said Mackey, “is those changes in our brain and our spinal cord, changes in our immune system that can occur, in our inflammatory system, can stay activated as if we're in this acute state.” 

Making things even more difficult, Mackey said the circuits involved with emotions are closely tied to circuits involved with pain, so the pain may be amplified by our feelings.

How the brain processes pain is something other Stanford researchers are working on in the labs* of Greg Scherrer and Mark Schnitzer. 

We sat down with Scherrer, a neuroscientist. “We are changing the focus of the field, in a way, trying to understand what the pain mechanisms are in the brain. The approach that has been used so far, which is to target the peripheral nervous system, hasn't worked very well.  So we decided to try something else,” said Scherrer. “We've found that there is a region in the brain that is known to be important for emotions that seems to have a critical role for generating the unpleasantness that we perceive during pain experiences.”

That region of the brain is the amygdala.  Scherrer and Schnitzer’s experiments were done in mice, which have similar anatomy to humans. So there is reason to believe the human brain may perceive pain the same way.

When Scherrer says “unpleasantness” he’s referring to the “hurt” of pain–what makes us say “ouch” when we hit our elbow. He says the brain registers two things; first, the impact or sensation that something has happened and second, the hurt or the “emotion” of pain. 

Monitoring mice brains with a microscope,  Scherrer and his team found that painful stimuli, like walking on a hot track, caused neurons to light up in the basolateral region of the amygdala. The researchers were able to temporarily disable this cluster of pain-detecting cells, and the mice behaved as if they no longer felt pain on the walking track. 

Scherrer says the next step is to determine whether human brains have similar cells that can be turned on or off. A drug or a device that erases the “hurt” of pain in humans, is still more than a decade away.

“So, the idea is to not make unpleasantness disappear completely, but make chronic pain more tolerable for patients,” said Scherrer. 

A non-addictive way to stop or reduce the unnecessary pain would be a miracle for Norris. To numb his discomfort, he was prescribed fentanyl, a powerful synthetic opioid.

“Fentanyl did a number on me. I was able to walk from the bed to the bathroom and back. But that was really about it. I mean I've had hallucinations, I’ve slept for days, been unable to sleep,” said Norris. “So finally after 10 years. I said that's it.”

While pain continues to be a constant presence in Norris’ life. He says his perspective has changed, love and friendship rescued him from its depths. “My wife made sure that I stayed social. She would have a party at the house, and we've got lots of friends in Hollywood, so she'd have 100 people or so. I'd wind up with 10 to 15 people in my bedroom, on my bed with me in my PJs, unable to get out of bed, just talking for hours.” 

A couple of times a year he gets epidurals to ease his discomfort and he’s now using virtual reality therapy to help him control how his body processes pain. 

“I can't do the exercises but what I could do the breathing and the concentration. And that has served me with VR. Because I can pull myself out of the pain. I can pull the pain away from me if I've got my act together,” said Norris.

Take a closer look at virtual reality therapy in part two of this story.

*Scherrer, moved his lab to the University of North Carolina, shortly after we interviewed him.


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