Neuroplasticity and chronic low back pain: an investigation into altered tactile discrimination, body schema and motor function.

Abstract

Chronic low back pain (CLBP) ranks 3rd in the Global Burden of Non-Communicable Diseases, behind heart disease and stroke and the problem is increasing with an aging and growing population. It is a painful, long-term condition contributing to increased morbidity, low quality-of-life and a significant socio-economic burden. Aetiologies are often unknown and unrelated to specific spinal pathology. Treatments typically focus on pain management and improving motor function. However, the outcomes are inadequate, remaining moderate at best with one approach no better than another. Sadly, many sufferers stop seeking help and their quality of life deteriorates. In other chronic pain conditions such as Phantom Limb Pain (PLP) and Complex Regional Pain Syndrome (CRPS), cortical neurophysiology and sensory outputs such as body schema and perception are altered alongside motor function impairments. Novel interventions to reverse these impairments coincide with reductions in pain intensity and perception. CLBP shares some characteristics with PLP and CRPS so it is plausible that novel interventions may improve CLBP outcomes. However, for intervention studies to be considered reliable they must be underpinned by robust research to identify the baseline characteristics within the population. This study explored sensory and motor characteristics in adults with CBLP. A systematic review of peer reviewed publications identified seven studies which utilised different techniques and populations to explore tactile discrimination, body schema and motor function. Critically, none explored all three and the review revealed the characteristics of these constructs to be unclear in the CLBP samples. A narrative synthesis concluded two-point discrimination threshold (TPDT) to be impaired at the anatomical region of pain. Limited evidence suggested that sub-groups within the CLBP group may exist and may be related to impaired body schema. Body schema impairment may also be anatomically linked. TPDT appears negatively correlated with body schema and lumbopelvic motor function but the relationship between body schema and motor control was unexplored. This study sought to address this gap by comparing key measures of TPDT, body schema (motor imagery performance and back perception) and motor function from 31 adults with CLBP which affected their activities of daily living (ADL’s), with an equivalent sized control group, within a UK context. Following two reliability studies to select appropriate methods of data collection, a cross-sectional research design identified differences between the two groups. Correlations between the key measures and pain, disability and kinesiophobia were explored. Significant differences between the groups were observed for measures of low back TPDT, back-perception and motor function, but not for measures of tactile threshold or motor imagery performance using left/right discrimination tasks. The left/right discrimination results and the predominantly absent correlations between the key variables differed from the findings in previous studies. New discoveries from this study included; 1) the most accurate and preferred tool to measure low back and fingertip TPDT was identified; 2) that Luomajoki’s Battery of Tests were reliable for use by registered chiropractors and osteopaths without the need for further training; 3) TPDT was impaired at and near to the ‘typical’ region of CLBP; 4) higher ‘typical’ pain scores moderately correlated with greater low back TPDT impairment; 5) a significant moderate positive correlation occurred between low back motor control and back perception scores; 6) this was the first study to explore tactile threshold, TPDT, body schema and motor function together in the same groups, and 7) it was the first to explore this combination of variables within the UK population. This study provides reliable baseline measures of factors known to be impaired in other chronic pain conditions. Small studies have found therapeutically targeting these factors reduces pain and disability in some chronic pain conditions. It is anticipated that this new knowledge may guide future sensorimotor therapeutic interventions to support pain management in those with CLBP.