Motor Imagery Performance and Tactile Spatial Acuity: Are They Altered in People with Frozen Shoulder?

Abstract

Frozen shoulder (adhesive capsulitis) is a severe chronic pain condition that is not well understood and current treatment is suboptimal. In several other chronic pain conditions motor imagery and tactile acuity deficits are present, which are thought to represent associated neuroplastic changes. The aims of this study were to determine if motor imagery performance assessed by the left/right judgement task, and tactile acuity assessed by two-point discrimination, are altered in people with unilateral frozen shoulder. In this cross-sectional, prospective study eighteen adults diagnosed with frozen shoulder in a physiotherapy clinic setting completed a left/right judgement task, response times (RT) and accuracy for the left/right judgement task were determined. Next, tactile acuity over both shoulders was assessed with a novel, force-standardised two-point discrimination test. Results corresponding to the affected side were compared to the pain free shoulder; Left/right judgement task: mean RT (SD) corresponding to the affected shoulder was significantly slower than RT for the healthy shoulder (p = 0.031). There was no side-to-side difference in accuracy (p > 0.05). Neither RT nor accuracy was related to pain/disability scores or duration of symptoms (p > 0.05). Two-point discrimination: mean two-point discrimination threshold of the affected shoulder was significantly larger than the contralateral healthy shoulder (p < 0.001). Two-point discrimination threshold was not related to pain/disability scores or pain duration (p > 0.05); One explanation for these findings is altered sensorimotor processing and/or disrupted sensorimotor cortex representations of the affected shoulder. A case then exists for the use of treatments aimed at reversing these changes, training the brain to reduce chronic shoulder pain.

Understanding the Left Right Judgement Test: A Literature Review

“…The effect of back and neck pain on the LRJT performance was controversial, which was consistent with the findings of a previously published meta-analysis study [8]. Although two-point discrimination test (TPDT) was usually conducted to investigate an alterations of primary somatosensory cortex (S1) representation [37,38,40,41,[45][46][47]49,51,53] and the results of TPDT was significantly difference from the healthy participants, the relationship between the LRJT and the TPDT was not statistically significant. Therefore, it can be suggested that peripheral pain may alter both motor and sensory cortical representations, but the interaction between two representations requires a further study.…”

“…Since Coslett et al [6,7] established the evidence of the effect of pain on motor imagery, the LRJT has been widely used for research in cohorts with pain. Most studies were conducted in patients with upper limb pain [37][38][39][40][41][42][43][44], including frozen shoulder, hand OA, carpal tunnel syndrome, wrist pain and lateral epicondylitis. The performance of the LRJT in patients with low limb pain [45][46][47][48], fibromyalgia [49] back and neck pain [50][51][52][53], and facial pain [54] was also investigated.…”

Functional cortical changes associated with shoulder instability – a systematic review

“…Furthermore, two-point discrimination was altered in patients with frozen shoulders when compared to controls 23 or the unaffected shoulder. 22 These studies indicate altered cortical function within certain shoulder pathologies. Therefore, it could be suggested that this may also be possible in patients with GHJ instability.…”

The Spatial Extent of Pain Is Associated with Pain Intensity, Catastrophizing and Some Measures of Central Sensitization in People with Frozen Shoulder

“…Taking into account that FS is characterized by being long-lasting, it is plausible that neuroplastic changes occurring at different levels of the central nervous system might contribute to pain maintenance [ 8 ]. Apart from some preliminary research [ 9 , 10 , 11 , 12 , 13 ], the implication of central pain mechanisms in people with FS remains uncertain. On the other hand, the role of low-grade inflammation and immune system response dysregulation leading to pathological changes in the shoulder capsule is gaining interest in the scientific literature [ 2 , 3 ].…”