Investigation of Central Pain Processing in Shoulder Pain: Converging Results From 2 Musculoskeletal Pain Models

Abstract

Recent reports suggest deficits in conditioned pain modulation (CPM) and enhanced suprathreshold heat pain response (SHPR) potentially play a role in the development of chronic pain. The purpose of this study was to investigate whether central pain processing was altered in 2 musculoskeletal shoulder pain models. The goals of this study were to determine whether central pain processing: 1) differs between healthy subjects and patients with clinical shoulder pain, 2) changes with induction of exercise induced muscle pain (EIMP), and 3) changes 3 months after shoulder surgery. Fifty eight patients with clinical shoulder pain and 56 age and sex matched healthy subjects were included in these analyses. The healthy cohort was examined before inducing EIMP, and 48 and 96 hours later. The clinical cohort was examined before shoulder surgery and 3 months later. CPM did not differ between the cohorts, however; SHPR was elevated for patients with shoulder pain compared to healthy controls. Induction of acute shoulder pain with EIMP resulted in increased shoulder pain intensity but did not change CPM or SHPR. Three months following shoulder surgery clinical pain intensity decreased but CPM was unchanged from pre-operative assessment. In contrast SHPR was decreased and showed values comparable with healthy controls at 3 months. Therefore, the present study suggests that: 1) clinical shoulder pain is associated with measurable changes in central pain processing, 2) exercise-induced shoulder pain did not affect measures of central pain processing, and 3) elevated SHPR was normalized with shoulder surgery. Collectively our findings support neuroplastic changes in pain modulation were associated with decreases in clinical pain intensity only, and could be detected more readily with thermal stimuli.

Dynamic, but not static, pain sensitivity predicts exercise-induced muscle pain: Covariation of temporal sensory summation and pain intensity

“…In that study, patients who showed reductions in TSS after surgery experienced clinically meaningful improvements in shoulder pain at three months post-intervention. In contrast those patients in whom there was no change in TSS after surgery continued to report pain and interference in daily activity at three months [24]. …”

“…The observed reductions in TSS after body-based interventions are therefore hypothesized to indicate changes that would be favorable for clinical outcome. Recent work supporting this theory indicates available plasticity within the nervous system (reductions in TSS after an intervention) to be prognostic of recovery from shoulder pain [24]. …”

The Comparative Effects of Spinal and Peripheral Thrust Manipulation and Exercise on Pain Sensitivity and the Relation to Clinical Outcome: A Mechanistic Trial Using a Shoulder Pain Model

“…20,21,36,37,53,61 Central sensitization has been linked to the progression and maintenance of chronic pain, and disrupting this process is paramount. 2,34 Thus, the changes in pain sensitivity that accompany shoulder pain provide a therapeutic target for manual therapy and a potential mechanism for its beneficial clinical effects.…”

Biopsychosocial influence on shoulder pain: Rationale and protocol for a pre-clinical trial

“…These measures were selected because we expected them to be responsive to the combined personalized intervention and associated with pain relief. For example, elevated suprathreshold heat pain responses normalized post-operatively in the clinical cohort [93] and its changes were associated with improvements in post-operative shoulder pain and disability [96]. …”