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Impaired Motor Imagery Linked to Peripheral Pain Conditions

Patients with chronic pain affecting the face and/or limbs demonstrated impaired motor imagery, but findings are not as clear-cut for spine and neck pain.

With John D. Breckenridge, PhD and Gabriel Sella, MD, PhD, MPH, MSc

Motor imagery is impaired in patients with chronic musculoskeletal pain, particularly in those with peripheral pain conditions affecting the face and limbs, according to research from Australian physiotherapist John D. Breckenridge, PhD, and his team at the University of Sydney Faculty of Medicine and Health.

However, in people who suffer from axial pain conditions (such as those affecting the head and neck), this relationship is not as clear-cut. These findings come from a comprehensive systematic review and meta-analysis1 that Dr. Breckenridge and his colleagues recently conducted from 25 studies representing a total of 2,266 participants with a variety of chronic pain conditions who performed left/right body part judgment task (LRJT).

Using LRJT to Measure Motor Imagery Performance

“The LRJT has been used in neuropsychological studies for several decades, and a large body of evidence points to it being a good measure of motor imagery performance,” Dr. Breckenridge told PPM. LRJT requires participants to view images of a body part and identify which side of the body each image belongs.Slower and inaccurate responses are often signs of altered proprioception (the mental image of the body in space), which may be linked with chronic pain.

“Until now, no comprehensive systematic review has been performed to pool the findings across multiple chronic pain conditions,” Dr. Breckenridge told PPM, adding that gleaning a better understanding of the relationship between LRJT and different types of chronic pain may help clinicians develop more effective treatment plans.

Patients with chronic pain affecting the face and/or limbs demonstrated impaired motor imagery, but findings are not as clear-cut for spine and neck pain. (Source: 123RF)

The Mental and Physical Connection

The peripheral pain conditions represented in Dr. Breckenridge’s review included complex regional pain syndrome (CRPS), upper limb fracture, carpal tunnel syndrome, phantom limb pain, brachial plexus avulsion, osteoarthritis, inflammatory arthritis, and upper and lower limb pain from various causes.

At the heart of the pain-to-LRJT relationship, he noted, is that the time it takes for a person to mentally envision moving a body part to match the image provided in LRJT corresponds with the time it takes for that person to perform the corresponding physical movement. In other words, for people with biomechanical constraints in their physical actions, LRJT results have shown a corresponding delay in their central processing, when compared with “healthy” or “pain-free” people, he explained.

Possible Theories to Explain Impaired LRJT Findings

In terms of how it works, “one theory is that when pain is persistent, otherwise pain-free stimuli becomes associated with pain—for example, moving a sore joint in a pain-free range becomes associated with pain, [moving the] joint more cautiously or slowly,” Dr. Breckenridge said. This is reflected in the LRJT because “we use similar mental processes to complete the task as we do when we move our limb to match the image.”

Gabriel Sella, MD, PhD, MPH, MSc, of the Ohio Valley Medical Center in Wheeling, WV, described another scenario. “If there is a brain injury—for example, a concussion—the proprioceptionmay be affected first, with the results that the position of the limbs or axial skeleton is reacting more slowly than in a healthy person,” he said.

Dr. Sella, who serves on PPM’s editorial advisory board, also suggested that the differences in how different areas of pain affect proprioception may account for variations in the LRJT results. “Any injury that affects the capsules in the joints will affect proprioception,” he said, pointing out that the limbs have many more such “relays” than the axial skeleton.

Differences in Peripheral and Axial Pain Responses

“The body creates an engram [mental picture] in the brain of the limbs, trunk, face, or neck very early in life [with the right and left strongly engrained]. The more we use the movements needed to create a function, the stronger the engram gets. Obviously, we do more ‘movement’ with the limbs and the face than with the neck or trunk,” Dr. Sella noted, which could help explain why there wasn’t a clear correlation with LRJT results and axial pain conditions.

Dr. Breckenridge offered another possible explanation for the lack of consistent evidence: “Back and neck pain can be one-sided, central, affect both sides, or it can change over time. This may have made the overall pooled effect inconsistent, so it could be that chronic spinal pain does affect motor imagery, but the inconsistencies mean it is difficult to capture a clear picture.”

The Need for Further Research, Treatment Approaches

Another potential reason for the differences in findings among peripheral and axial pain conditions may have to do with the meta-analysis itself, which includedmany more peripheral studies than axial studies, meaning there may not be enough data available to gain meaningful insight, Dr. Breckenridge said. He pointed out, however, that the evidence may change over time as more research becomes available. “It could also be that the current LRJT tests for axial conditions are not sensitive enough,” he added.

While this leaves clinicians with inconclusive results for axial conditions, Dr. Breckenridge stressed that for practitioners treating peripheral pain, the findings may be especially helpful. Patients with peripheral conditions may benefit “from using graded motor imagery [that includes LRJT as well as mirror therapy]. This treatment aims to restore disrupted body schema [a collection of integrated body maps held in the brain that assist with movement] and has proven useful in the treatment of CRPS and chronic upper limb pain,” Dr. Breckenridge said.

Dr. Sella added that, “Another possible treatment for clinicians to consider for people presenting with peripheral pain is surface electromyography (SEMG)-assisted biofeedback [a treatment that incorporates visualization] to restore the disrupted body schema. I have found this to be a very useful restorative method for proprioception loss.”

He also stressed that the overall takeaway of thisreview for clinicians is to “pay more attention to the presence of proprioception dysfunction in any injury, especially that of the limbs. This needs to be considered both at the diagnostic time and also at the rehabilitation period.”

Last updated on: May 3, 2019
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