Should central pain be sub-classified? A hypothesis of Musculoskeletal Body Image Pain - initial insights into diagnostic criteria

Background:

Sub-classification of pain mechanisms is recommended over time frame based pain classification. The concept of central sensitization (CS) has been critical to interpreting pain presentations. Despite the importance, CS does not adequately explain complex presentations such as: phantom limb pain, complex regional pain syndrome, fibromyalgia, thalamic pain, zero gravity symptoms or laboratory induced sensory incongruence. These presentations are either left unexplained, sub-grouped along with CS or labeled as "dysfunctional pain". An understanding of the characteristics of these presentations can lead to a diagnosis and treatment strategies.

Purpose:

The purpose of this study was describe the clinical characteristics of a sub-group of dysfunctional pain patients that could not be sub-classified by a pain mechanism to provide a preliminary strategy to diagnosis of a possible separate central pain mechanism.

Methods:

A chart review was done to collect self report and physical assessment items for 131 patients who had dysfunctional pain.  They were dichotomized into (1) those who did not fit a preliminary clinical prediction rule for CS and did not have neuro-immune-endocrine-autonomic symptoms in all bodily systems (NSB) (2) and those that did (SB). Descriptive statistics were used to describe items relating to central pain. The items were dichotomized into being present or not being present. Those which were present in over 80% of subjects were placed in a standard 2 x 2 table to calculate odds ratios (OR). Sensitivity (SN) and specificity (SP) were also calculated to provide initial insights into diagnostic accuracy.

Results:

The self report items identified were the Kinesthetic and Visual Imagery Questionnaire (KVIQ) and Body Image Drawing (BID). The physical assessment were the Cross March Midline Test (CM) and the Infinity Pattern (IP) Oculomotor Test. The OR of NSB were: KVIQ: 26; BID: 114; CM: 1.88; IP: 1.50. The SN and SP of NSB were: KVIQ: 0.92, 0.70; BID: 0.99, 0.62; CM: 0.97, 0.66; IP: 0.88, 0.64, respectively.

Conclusion(s):

Musculoskeletal body image pain (MBIP) may be a unique sub-group of central pain. Preliminary findings suggest that it may be identified by the inability to perform internal intrinsic motor imagery, the inability to draw the outline of their body image, or use their  symptoms as feedback for drawing, and poor ability to cross midline. This group lacks extreme widespread sensory hypersensitivity, as assessed by quantitative sensory testing, and high constant pain. MBIP provides a logical sub-classification of other central or dysfunctional pain syndromes by adapting Moseley's definition of pain. Here, the "threat" may be interpreted as the brain not knowing what is happening in the body. The result is that pain and musculoskeletal symptoms are produced to act as a default sensory system. Further research is needed to confirm the validity of MBIP and the diagnostic accuracy.

Implications:

Clinicians can use the self report and physical assessment items to help differentiate MBIP from central sensitization. SP and SN should be interpreted with caution since there is no true gold standard established.

Reference as: Gibbons SGT 2016 Can a strategy for motor imagery relearning used in learning difficulties be used for complex pain presentations? A case series. Proceedings of "Expanding Horizons": The 11th International Conference of IFOMT. July 4-8; Glasgow, Scotland

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Facilitator

Sean Gibbons graduated from Manchester University in 1995. He has been rehabilitating movement patterns, chronic pain and concussion for over 20 years. His PhD was on the development of the Motor Control Abilities Questionnaire which predicts motor skill learning. His research has found that the questionnaire is more predictive of monitoring outcome than the Rivermead Concussion Questionnaire. His research has identified key new sub-classifications relevant for Concussion: Neurological Factors; Midline as a sensory system and Chronic Low Grade Systemic Inflammation. His current work follows this and aims to further understand the mechanisms of poor outcome and the Individual Factors influencing treatment. His dissection and research into psoas major, gluteus maximus and other muscles has led to the development of new rehabilitation options. He has presented his research at national and international conferences and has several journal publications and book chapters on related topics. He is an Assistant Clinical Professor (Adjunct) at McMaster's Advanced Orthopaedic Musculoskeletal / Manipulative Physiotherapy specialization and lectures at Manchester Metropolitan University's Masters in Advanced Physiotherapy program.