Hendrik van de Meent, et al.
PAIN
April 2011 / Volume 152

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Why Review this Article?
Many people with CRPS find relief in movement. Jennifer Smith, who we hear from in Episode 1, uses movement to manage her pain. Understanding how physical activity and CRPS pain are interconnected can be integral for pain management.

Purpose
Pain exposure physical therapy (PEPT) consists of a progressive-loading exercise program and management of pain-avoidance behavior without the use of specific CRPS-1 medication or analgesics. Prior to this study, no research had been done on PEPT and CRPS. The goal of this study was to demonstrate if this type of treatment was both safe and effective.

Methods
In this study, patients were enrolled in a PEPT program over the course of 12 months. During this program, they were weaned off any medications for their CRPS, and were put on a progressive loading program. The program was designed around specific, patient chosen movement goals. Additionally, a lot of cognitive behavioral work was embedded into the programming. All conscious and unconscious signs of catastrophizing and kinesiophobic behavior talked through with the patient. If they could not overcome their fear or felt doubt about the treatment, it was stopped.

Results
In terms of safety, no one’s CRPS worsened throughout the course of the program. In fact, over the course of treatment, there was a statistically significant decrease in pain — 35%! Patients in the program showed a 25% increase in their walking speed, and ratings of disability dropped by 60%. Kinesiophobia (fear of movement) decreased by 18% at the end of the study, and quality of life improved a whopping 269%! Additionally, many other physical factors showed a significant improvement, including hand range of motion, grip strength, arm activity, and plantar flexion strength.

So What Does It Mean?
Although movement is scary and causes initial pain for CRPS patients, consistent movement is significantly connected to better long term health outcomes in terms of pain and quality of life — as well as many other important factors. Furthermore, and importantly, there are no harmful side effects from movement!

Limitations
This study was done with a very small sample size as it was intended to be a preliminary study for a larger RCT.

Lorimer Moseley, et al.
Arthritis & Rheumatism
May 2008 / Volume 59 / Number 5

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Why Review This Article?
Lorimer Moseley is to pain science what John Lennon is to rock and roll. Moseley is responsible for writing Explain Pain, a fantastic resource for people with chronic pain to gain a better understanding of pain’s biology and to learn effective ways to manage it. This article helps us understand the link between physical pain and mental pain, which is a topic touched on by almost everyone who speaks on the podcast.

Purpose
CRPS is associated with pain on movement, which is presumed to be caused by noxious stimulation. This study investigated whether motor imagery, in the absence of movement, increases CRPS symptoms of pain and swelling.

Methods
A motor imagery task was given to patients with CRPS and healthy controls. In this task, participants were shown images of left and right arms and hands and told to think about how they would perform the movement to achieve the position shown. They would then process a button and repeat this task with a new image. This kind of task engages our mind’s understanding of a body schema (ie, how we might have to move our body in space).

Measurements of the subjects pain (using a visual analog scale) and swelling (using direct measurement) were taken before, during, and 60 minutes after the experiment. Participants were also asked to rate how vividly they imagined these movements, and to rate their own level of catastrophizing and fear of movement.

Results
Imagining movement in the motor imagery task resulted in a significant increase in pain and swelling for people with CRPS. Pain and swelling were positively correlated with participants who said they had higher levels of catastrophizing and greater fear of movement. Additionally, the more vividly the participants imagined their movements, the higher their pain and swelling were.

So What Does It Mean?
Moseley concludes that it would be wise to “train the brain before you train the body.” If we react to thinking about pain with increased symptoms, through cognitive retraining, we can teach the brain that this, in fact, is not a painful stimulus. This was shown by the fact that people who had lower fear and lower catastrophizing experienced less pain in the task. Learning to manage the fear around movement can potentially enable more pain-free movement.

Limitations
This study had a small sample size, so may have limited statistical power to extrapolate to a larger population of those with CRPS. Additionally, neither brain conductivity nor temperature was measured as a signal of arousal.

Peter D. Drummond, Philip M. Finch
PAIN
April 2023 / Volume 164 / Number 4

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Why Review this Article?
This is hot off the press, 2023 research on CRPS! This line of research that aims to understand the impact of chronic pain on other forms of sensation, like hearing.

Helpful Definitions:
hyperacusis: reduced tolerance to sound

ipsilateral: happening on the same side of the body (eg: if you have pain in your right arm, your right leg is considered ipsilateral to the painful limb)

contralateral: happening on the opposite side of the body (eg: if you have pain in your right arm, your left arm is considered contralateral to the pain)

Purpose
Previous research has shown that people with CRPS have hyperacusis (reduced sound tolerance) on the ipsilateral side (same side) of where their CRPS pain originated. Hyperacusis usually stems from the brain “turning up the signals” to compensate for peripheral hearing loss. This study’s aim was to understand if people who had CRPS had hyperacusis due to actual damage to their cochlea or do to some other brain process that diminished their tolerance for noise.

Methods
The researchers recruited 30 people with CRPS (27 women and 9 men aged between 23 and 70 years), and a control group of 19 women and 7 men aged between
24 and 74 years (mean age 44.8 years) without chronic pain. Participant’s hearing threshold was measured in a first experiment by signaling whether or not they heard certain tones. In a second experiment, the experimenters played tones of increasing loudness, and allowed participants to indicate when they experienced the noise as painful. In a third experiment, speed of electrical signals inside the brain were measured when participants heard a click.

Results
The experiment found that CRPS patients did not have a significant difference in their hearing ability (ie, there was no difference for CRPS patients contralaterally or ipsilaterally compared to controls). However, they did discover that on the CRPS-affected side, patients had a significantly lower auditory discomfort threshold than compared contralateral side or the controls. Additionally, they found from measuring the brain’s electrical signals that the response to sound lasted longer on the CRPS affected side than in controls.

So What Does It Mean?
This study showed that auditory discomfort to sound for patients with CRPS was only present on the affected side of their body. More importantly, it showed that this auditory discomfort didn’t stem from hearing loss, but rather a difference in processing of auditory signals. Those with CRPS had greater ipsilateral brainstem activity which perpetuated signals longer than on their contralateral side or in healthy controls. This is interesting because it points to a reduction of inhibitory processes that might regulate how those with CRPS perceive pain.

Limitations
This study was only conducted on people with CRPS type 2. Additionally, participants with CRPS were often on medications (eg, psychoactive, anti-convulsive, anti-inflammatory, or analgesic drugs), which the researchers did not control for. It is unclear if these drugs impact the brain’s processing of auditory signals.