Low Back Pain: The Potential Contribution of Supraspinal Motor Control and Proprioception
SOURCE: Neuroscientist. 2018 (Nov 2) [Epub]
Michael Lukas Meier, Andrea Vrana1, and Petra Schweinhardt
Integrative Spinal Research,
Department of Chiropractic Medicine,
University Hospital Balgrist,
Motor control, which relies on constant communication between motor and sensory systems, is crucial for spine posture, stability and movement. Adaptions of motor control occur in low back pain (LBP) while different motor adaption strategies exist across individuals, probably to reduce LBP and risk of injury. However, in some individuals with LBP, adapted motor control strategies might have long-term consequences, such as increased spinal loading that has been linked with degeneration of intervertebral discs and other tissues, potentially maintaining recurrent or chronic LBP. Factors contributing to motor control adaptations in LBP have been extensively studied on the motor output side, but less attention has been paid to changes in sensory input, specifically proprioception.
Furthermore, motor cortex reorganization has been linked with chronic and recurrent LBP, but underlying factors are poorly understood. Here, we review current research on behavioral and neural effects of motor control adaptions in LBP. We conclude that back pain-induced disrupted or reduced proprioceptive signaling likely plays a pivotal role in driving long-term changes in the top-down control of the motor system via motor and sensory cortical reorganization. In the outlook of this review, we explore whether motor control adaptations are also important for other (musculoskeletal) pain conditions.
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KEYWORDS: chronic pain; low back pain; motor control; motor cortex; muscle spindle; proprioception; somatosensory cortex
From the Full-Text Article:
Low back pain (LBP) is extremely common with a lifetime prevalence around 75% to 84% [Thiese and others 2014] and is globally among the health conditions with the highest numbers of years lived with disability [Vos and others 2017]. In most instances of LBP, no underlying pathology can be identified [Maher and others 2016], resulting in the unfortunate diagnosis of “non-specific LBP” (nsLBP). An acute episode of LBP spontaneously resolves in one third of the patients within the first 3 months; however, about 65% of the patients still experience LBP 1 year after LBP onset [Itz and others 2013]. Consequently, recurrent or chronic LBP (LBP persisting for 12 weeks or more) is a common problem, with an enormous individual, economic and societal burden [Hoy and others 2014; van Tulder and others 2006].
Therefore, advancing the understanding of factors contributing to the chronification of LBP is a research priority [Hartvigsen and others 2018]. Among factors such as genetic, physical and psychosocial features, adaptions of motor control likely play a significant role in chronic or recurrent LBP [Hodges and others 2013] because they are associated with several important factors contributing to LBP chronification, including increased spinal tissue strains due to potential loss of trunk control and enhanced trunk muscle co-contraction, resulting in muscle fatigue [Madeleine 2010; van Dieën and others 2018b]. Both factors, loss of trunk control and enhanced muscle co-contraction, have been linked with sustained mechanical loading on spinal tissues, conceivably potentiating degeneration of intervertebral discs and other tissues [Lotz and Chin 2000; Paul and others 2013; Urban and Roberts 2003; van Dieën and thers 2018b].
The overarching hypothesis of this review is that motor control adaptions induced by acute LBP play an important role in the chronification of LBP. Following a short introduction to human motor control and proprioception, we summarize the findings on motor control adaptions in LBP on the behavioral and neural level, including (supra-)spinal and psychological contributions. We integrate new research suggesting a powerful role of reduced paraspinal proprioceptive input for the top-down control of cortical sensorimotor circuits, probably associated with neuroplastic changes. The resulting cortical reorganization would potentially explain persistent and dysfunctional motor control adaptions associated with LBP chronification.